pkg/compiler: move bitfield marking from sys

7 files changed, 191 insertions, 232 deletions

diff --git a/sys/align.go b/sys/align.go
index 08f1acb03..1be1ccc82 100644
--- a/sys/align.go
+++ b/sys/align.go
@@ -22,7 +22,6 @@ func initAlign() {
 					rec(f)
 				}
 				t1.Varlen() // dummy call to initialize t1.varlen
-				markBitfields(t1)
 				addAlignment(t1)
 			}
 		case *UnionType:
@@ -42,46 +41,6 @@ func initAlign() {
 	}
 }
 
-func setBitfieldOffset(t Type, offset uint64, last bool) {
-	switch t1 := t.(type) {
-	case *IntType:
-		t1.BitfieldOff = offset
-		t1.BitfieldLst = last
-	case *ConstType:
-		t1.BitfieldOff = offset
-		t1.BitfieldLst = last
-	case *LenType:
-		t1.BitfieldOff = offset
-		t1.BitfieldLst = last
-	case *FlagsType:
-		t1.BitfieldOff = offset
-		t1.BitfieldLst = last
-	case *ProcType:
-		t1.BitfieldOff = offset
-		t1.BitfieldLst = last
-	default:
-		panic(fmt.Sprintf("type %+v can't be a bitfield", t1))
-	}
-}
-
-func markBitfields(t *StructType) {
-	var bfOffset uint64
-	for i, f := range t.Fields {
-		if f.BitfieldLength() == 0 {
-			continue
-		}
-		off, last := bfOffset, false
-		bfOffset += f.BitfieldLength()
-		if i == len(t.Fields)-1 || // Last bitfield in a group, if last field of the struct...
-			t.Fields[i+1].BitfieldLength() == 0 || // or next field is not a bitfield...
-			f.Size() != t.Fields[i+1].Size() || // or next field is of different size...
-			bfOffset+t.Fields[i+1].BitfieldLength() > f.Size()*8 { // or next field does not fit into the current group.
-			last, bfOffset = true, 0
-		}
-		setBitfieldOffset(f, off, last)
-	}
-}
-
 func addAlignment(t *StructType) {
 	if t.IsPacked {
 		// If a struct is packed, statically sized and has explicitly set alignment, add a padding.
diff --git a/sys/decl.go b/sys/decl.go
index fe5744648..4295b014c 100644
--- a/sys/decl.go
+++ b/sys/decl.go
@@ -123,9 +123,9 @@ func (t *ResourceType) Align() uint64 {
 type IntTypeCommon struct {
 	TypeCommon
 	TypeSize    uint64
-	BigEndian   bool
 	BitfieldOff uint64
 	BitfieldLen uint64
+	BigEndian   bool
 	BitfieldLst bool
 }
 
diff --git a/sys/sys_386.go b/sys/sys_386.go
index f29514dce..61d65f2c1 100644
--- a/sys/sys_386.go
+++ b/sys/sys_386.go
@@ -482,11 +482,11 @@ var structFields = []*StructFields{
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "dst_port"}, TypeSize: 2, BigEndian: true}, ValuesStart: 20000, ValuesPerProc: 4},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "offset"}, TypeSize: 1}, ByteSize: 4, Buf: "parent"},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "cscov"}, TypeSize: 1, BitfieldLen: 4}, Val: 1},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "parent", Protocol: 33},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "x"}, TypeSize: 1, BitfieldLen: 1}},
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldLen: 3}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldOff: 5, BitfieldLen: 3, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "seq_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "ack_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
@@ -1488,9 +1488,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmp_ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "total_len"}, TypeSize: 2, BigEndian: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -1602,7 +1602,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmpv6_ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "length"}, TypeSize: 2, BigEndian: true}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2062,9 +2062,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "total_len"}, TypeSize: 2, BigEndian: true}, Buf: "ipv4_packet"},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -2136,7 +2136,7 @@ var structFields = []*StructFields{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 1}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "pointer"}, TypeSize: 1}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_flags", FldName: "flg"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "timestamps"}, Type: &StructType{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_timestamp"}, IsPacked: true}},
 	}},
 	{Key: StructKey{Name: "ipv4_option_timestamp_timestamp"}, Fields: []Type{
@@ -2255,8 +2255,8 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_hi"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "m_flag"}, TypeSize: 1, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldLen: 5}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 2}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldOff: 3, BitfieldLen: 5, BitfieldLst: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "identification"}, TypeSize: 4}, ValuesStart: 100, ValuesPerProc: 4},
 	}},
 	{Key: StructKey{Name: "ipv6_hopots_ext_header"}, Fields: []Type{
@@ -2275,7 +2275,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 2, BigEndian: true}, Buf: "payload"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2878,13 +2878,13 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "kvm_setup_opt_vmwrite"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "typ"}, TypeSize: 8}, Val: 8},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "sz"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldLen: 5}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldLen: 48}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldOff: 1, BitfieldLen: 5}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldOff: 6, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldOff: 10, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldOff: 12, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldOff: 13, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldOff: 15, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldOff: 16, BitfieldLen: 48, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "kvm_setup_opt_x86"}, Fields: []Type{
 		&StructType{TypeCommon: TypeCommon{TypeName: "kvm_setup_opt_cr0", FldName: "cr0"}},
@@ -4828,13 +4828,13 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct0"}, Fields: []Type{
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10}, Vals: []uint64{0, 1, 2}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10, BitfieldLst: true}, Vals: []uint64{0, 1, 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f2"}, TypeSize: 2, BitfieldLen: 5}, Val: 66},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldLen: 6}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15}, Val: 66},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11}, Buf: "parent"},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BigEndian: true, BitfieldLen: 11}, Buf: "parent"},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldOff: 5, BitfieldLen: 6, BitfieldLst: true}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15, BitfieldLst: true}, Val: 66},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11, BitfieldLst: true}, Buf: "parent"},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BitfieldLen: 11, BigEndian: true, BitfieldLst: true}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f7"}, TypeSize: 1}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1"}, Fields: []Type{
@@ -4843,15 +4843,15 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1_internal"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "syz_csum_encode"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f0"}, TypeSize: 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "f1"}, TypeSize: 2, BigEndian: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f2"}, Type: &IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32"}, TypeSize: 4}}, Kind: 1, RangeEnd: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f3"}, TypeSize: 1, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f5"}, Kind: 1, RangeBegin: 4, RangeEnd: 4},
 	}},
 	{Key: StructKey{Name: "syz_csum_icmp_packet"}, Fields: []Type{
@@ -4925,12 +4925,12 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_length_bf_struct_inner"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f4"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldOff: 16, BitfieldLen: 16, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f7"}, TypeSize: 4}, Buf: "parent"},
 	}},
 	{Key: StructKey{Name: "syz_length_bytesize2_struct"}, Fields: []Type{
@@ -5140,8 +5140,8 @@ var structFields = []*StructFields{
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "seq_num"}},
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "ack_num"}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ns"}, TypeSize: 1, BitfieldLen: 1}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldLen: 3}},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 3}},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, ByteSize: 4, Buf: "parent"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "tcp_flags", FldName: "flags"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 8, 16, 32, 64, 128, 194}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "window_size"}, TypeSize: 2, BigEndian: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "tcp_packet", Protocol: 6},
@@ -5550,14 +5550,14 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "vlan_tag_ad"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 37120},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vlan_tag_q"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 33024},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vt_consize"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "rows"}, TypeSize: 2}},
diff --git a/sys/sys_amd64.go b/sys/sys_amd64.go
index 7c5beaf04..5a0403a84 100644
--- a/sys/sys_amd64.go
+++ b/sys/sys_amd64.go
@@ -482,11 +482,11 @@ var structFields = []*StructFields{
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "dst_port"}, TypeSize: 2, BigEndian: true}, ValuesStart: 20000, ValuesPerProc: 4},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "offset"}, TypeSize: 1}, ByteSize: 4, Buf: "parent"},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "cscov"}, TypeSize: 1, BitfieldLen: 4}, Val: 1},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "parent", Protocol: 33},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "x"}, TypeSize: 1, BitfieldLen: 1}},
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldLen: 3}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldOff: 5, BitfieldLen: 3, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "seq_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "ack_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
@@ -1488,9 +1488,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmp_ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "total_len"}, TypeSize: 2, BigEndian: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -1602,7 +1602,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmpv6_ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "length"}, TypeSize: 2, BigEndian: true}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2062,9 +2062,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "total_len"}, TypeSize: 2, BigEndian: true}, Buf: "ipv4_packet"},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -2136,7 +2136,7 @@ var structFields = []*StructFields{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 1}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "pointer"}, TypeSize: 1}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_flags", FldName: "flg"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "timestamps"}, Type: &StructType{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_timestamp"}, IsPacked: true}},
 	}},
 	{Key: StructKey{Name: "ipv4_option_timestamp_timestamp"}, Fields: []Type{
@@ -2255,8 +2255,8 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_hi"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "m_flag"}, TypeSize: 1, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldLen: 5}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 2}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldOff: 3, BitfieldLen: 5, BitfieldLst: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "identification"}, TypeSize: 4}, ValuesStart: 100, ValuesPerProc: 4},
 	}},
 	{Key: StructKey{Name: "ipv6_hopots_ext_header"}, Fields: []Type{
@@ -2275,7 +2275,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 2, BigEndian: true}, Buf: "payload"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2878,13 +2878,13 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "kvm_setup_opt_vmwrite"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "typ"}, TypeSize: 8}, Val: 8},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "sz"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldLen: 5}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldLen: 48}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldOff: 1, BitfieldLen: 5}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldOff: 6, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldOff: 10, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldOff: 12, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldOff: 13, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldOff: 15, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldOff: 16, BitfieldLen: 48, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "kvm_setup_opt_x86"}, Fields: []Type{
 		&StructType{TypeCommon: TypeCommon{TypeName: "kvm_setup_opt_cr0", FldName: "cr0"}},
@@ -4828,13 +4828,13 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct0"}, Fields: []Type{
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10}, Vals: []uint64{0, 1, 2}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10, BitfieldLst: true}, Vals: []uint64{0, 1, 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f2"}, TypeSize: 2, BitfieldLen: 5}, Val: 66},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldLen: 6}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15}, Val: 66},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11}, Buf: "parent"},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BigEndian: true, BitfieldLen: 11}, Buf: "parent"},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldOff: 5, BitfieldLen: 6, BitfieldLst: true}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15, BitfieldLst: true}, Val: 66},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11, BitfieldLst: true}, Buf: "parent"},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BitfieldLen: 11, BigEndian: true, BitfieldLst: true}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f7"}, TypeSize: 1}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1"}, Fields: []Type{
@@ -4843,15 +4843,15 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1_internal"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "syz_csum_encode"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f0"}, TypeSize: 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "f1"}, TypeSize: 2, BigEndian: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f2"}, Type: &IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32"}, TypeSize: 4}}, Kind: 1, RangeEnd: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f3"}, TypeSize: 1, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f5"}, Kind: 1, RangeBegin: 4, RangeEnd: 4},
 	}},
 	{Key: StructKey{Name: "syz_csum_icmp_packet"}, Fields: []Type{
@@ -4925,12 +4925,12 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_length_bf_struct_inner"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f4"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldOff: 16, BitfieldLen: 16, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f7"}, TypeSize: 4}, Buf: "parent"},
 	}},
 	{Key: StructKey{Name: "syz_length_bytesize2_struct"}, Fields: []Type{
@@ -5140,8 +5140,8 @@ var structFields = []*StructFields{
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "seq_num"}},
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "ack_num"}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ns"}, TypeSize: 1, BitfieldLen: 1}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldLen: 3}},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 3}},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, ByteSize: 4, Buf: "parent"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "tcp_flags", FldName: "flags"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 8, 16, 32, 64, 128, 194}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "window_size"}, TypeSize: 2, BigEndian: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "tcp_packet", Protocol: 6},
@@ -5550,14 +5550,14 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "vlan_tag_ad"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 37120},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vlan_tag_q"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 33024},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vt_consize"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "rows"}, TypeSize: 2}},
diff --git a/sys/sys_arm.go b/sys/sys_arm.go
index a15465aca..b46740a5f 100644
--- a/sys/sys_arm.go
+++ b/sys/sys_arm.go
@@ -482,11 +482,11 @@ var structFields = []*StructFields{
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "dst_port"}, TypeSize: 2, BigEndian: true}, ValuesStart: 20000, ValuesPerProc: 4},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "offset"}, TypeSize: 1}, ByteSize: 4, Buf: "parent"},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "cscov"}, TypeSize: 1, BitfieldLen: 4}, Val: 1},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "parent", Protocol: 33},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "x"}, TypeSize: 1, BitfieldLen: 1}},
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldLen: 3}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldOff: 5, BitfieldLen: 3, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "seq_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "ack_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
@@ -1488,9 +1488,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmp_ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "total_len"}, TypeSize: 2, BigEndian: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -1602,7 +1602,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmpv6_ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "length"}, TypeSize: 2, BigEndian: true}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2062,9 +2062,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "total_len"}, TypeSize: 2, BigEndian: true}, Buf: "ipv4_packet"},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -2136,7 +2136,7 @@ var structFields = []*StructFields{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 1}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "pointer"}, TypeSize: 1}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_flags", FldName: "flg"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "timestamps"}, Type: &StructType{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_timestamp"}, IsPacked: true}},
 	}},
 	{Key: StructKey{Name: "ipv4_option_timestamp_timestamp"}, Fields: []Type{
@@ -2255,8 +2255,8 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_hi"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "m_flag"}, TypeSize: 1, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldLen: 5}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 2}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldOff: 3, BitfieldLen: 5, BitfieldLst: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "identification"}, TypeSize: 4}, ValuesStart: 100, ValuesPerProc: 4},
 	}},
 	{Key: StructKey{Name: "ipv6_hopots_ext_header"}, Fields: []Type{
@@ -2275,7 +2275,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 2, BigEndian: true}, Buf: "payload"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2878,13 +2878,13 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "kvm_setup_opt_vmwrite"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "typ"}, TypeSize: 8}, Val: 8},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "sz"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldLen: 5}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldLen: 48}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldOff: 1, BitfieldLen: 5}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldOff: 6, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldOff: 10, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldOff: 12, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldOff: 13, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldOff: 15, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldOff: 16, BitfieldLen: 48, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "kvm_setup_opt_x86"}, Fields: []Type{
 		&StructType{TypeCommon: TypeCommon{TypeName: "kvm_setup_opt_cr0", FldName: "cr0"}},
@@ -4828,13 +4828,13 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct0"}, Fields: []Type{
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10}, Vals: []uint64{0, 1, 2}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10, BitfieldLst: true}, Vals: []uint64{0, 1, 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f2"}, TypeSize: 2, BitfieldLen: 5}, Val: 66},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldLen: 6}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15}, Val: 66},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11}, Buf: "parent"},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BigEndian: true, BitfieldLen: 11}, Buf: "parent"},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldOff: 5, BitfieldLen: 6, BitfieldLst: true}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15, BitfieldLst: true}, Val: 66},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11, BitfieldLst: true}, Buf: "parent"},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BitfieldLen: 11, BigEndian: true, BitfieldLst: true}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f7"}, TypeSize: 1}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1"}, Fields: []Type{
@@ -4843,15 +4843,15 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1_internal"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "syz_csum_encode"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f0"}, TypeSize: 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "f1"}, TypeSize: 2, BigEndian: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f2"}, Type: &IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32"}, TypeSize: 4}}, Kind: 1, RangeEnd: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f3"}, TypeSize: 1, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f5"}, Kind: 1, RangeBegin: 4, RangeEnd: 4},
 	}},
 	{Key: StructKey{Name: "syz_csum_icmp_packet"}, Fields: []Type{
@@ -4925,12 +4925,12 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_length_bf_struct_inner"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f4"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldOff: 16, BitfieldLen: 16, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f7"}, TypeSize: 4}, Buf: "parent"},
 	}},
 	{Key: StructKey{Name: "syz_length_bytesize2_struct"}, Fields: []Type{
@@ -5140,8 +5140,8 @@ var structFields = []*StructFields{
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "seq_num"}},
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "ack_num"}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ns"}, TypeSize: 1, BitfieldLen: 1}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldLen: 3}},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 3}},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, ByteSize: 4, Buf: "parent"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "tcp_flags", FldName: "flags"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 8, 16, 32, 64, 128, 194}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "window_size"}, TypeSize: 2, BigEndian: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "tcp_packet", Protocol: 6},
@@ -5550,14 +5550,14 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "vlan_tag_ad"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 37120},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vlan_tag_q"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 33024},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vt_consize"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "rows"}, TypeSize: 2}},
diff --git a/sys/sys_arm64.go b/sys/sys_arm64.go
index d4616b469..35f037ae0 100644
--- a/sys/sys_arm64.go
+++ b/sys/sys_arm64.go
@@ -482,11 +482,11 @@ var structFields = []*StructFields{
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "dst_port"}, TypeSize: 2, BigEndian: true}, ValuesStart: 20000, ValuesPerProc: 4},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "offset"}, TypeSize: 1}, ByteSize: 4, Buf: "parent"},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "cscov"}, TypeSize: 1, BitfieldLen: 4}, Val: 1},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "parent", Protocol: 33},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "x"}, TypeSize: 1, BitfieldLen: 1}},
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldLen: 3}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldOff: 5, BitfieldLen: 3, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "seq_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "ack_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
@@ -1488,9 +1488,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmp_ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "total_len"}, TypeSize: 2, BigEndian: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -1602,7 +1602,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmpv6_ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "length"}, TypeSize: 2, BigEndian: true}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2062,9 +2062,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "total_len"}, TypeSize: 2, BigEndian: true}, Buf: "ipv4_packet"},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -2136,7 +2136,7 @@ var structFields = []*StructFields{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 1}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "pointer"}, TypeSize: 1}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_flags", FldName: "flg"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "timestamps"}, Type: &StructType{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_timestamp"}, IsPacked: true}},
 	}},
 	{Key: StructKey{Name: "ipv4_option_timestamp_timestamp"}, Fields: []Type{
@@ -2255,8 +2255,8 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_hi"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "m_flag"}, TypeSize: 1, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldLen: 5}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 2}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldOff: 3, BitfieldLen: 5, BitfieldLst: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "identification"}, TypeSize: 4}, ValuesStart: 100, ValuesPerProc: 4},
 	}},
 	{Key: StructKey{Name: "ipv6_hopots_ext_header"}, Fields: []Type{
@@ -2275,7 +2275,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 2, BigEndian: true}, Buf: "payload"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2878,13 +2878,13 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "kvm_setup_opt_vmwrite"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "typ"}, TypeSize: 8}, Val: 8},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "sz"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldLen: 5}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldLen: 48}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldOff: 1, BitfieldLen: 5}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldOff: 6, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldOff: 10, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldOff: 12, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldOff: 13, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldOff: 15, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldOff: 16, BitfieldLen: 48, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "kvm_setup_opt_x86"}, Fields: []Type{
 		&StructType{TypeCommon: TypeCommon{TypeName: "kvm_setup_opt_cr0", FldName: "cr0"}},
@@ -4828,13 +4828,13 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct0"}, Fields: []Type{
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10}, Vals: []uint64{0, 1, 2}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10, BitfieldLst: true}, Vals: []uint64{0, 1, 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f2"}, TypeSize: 2, BitfieldLen: 5}, Val: 66},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldLen: 6}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15}, Val: 66},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11}, Buf: "parent"},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BigEndian: true, BitfieldLen: 11}, Buf: "parent"},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldOff: 5, BitfieldLen: 6, BitfieldLst: true}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15, BitfieldLst: true}, Val: 66},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11, BitfieldLst: true}, Buf: "parent"},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BitfieldLen: 11, BigEndian: true, BitfieldLst: true}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f7"}, TypeSize: 1}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1"}, Fields: []Type{
@@ -4843,15 +4843,15 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1_internal"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "syz_csum_encode"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f0"}, TypeSize: 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "f1"}, TypeSize: 2, BigEndian: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f2"}, Type: &IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32"}, TypeSize: 4}}, Kind: 1, RangeEnd: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f3"}, TypeSize: 1, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f5"}, Kind: 1, RangeBegin: 4, RangeEnd: 4},
 	}},
 	{Key: StructKey{Name: "syz_csum_icmp_packet"}, Fields: []Type{
@@ -4925,12 +4925,12 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_length_bf_struct_inner"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f4"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldOff: 16, BitfieldLen: 16, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f7"}, TypeSize: 4}, Buf: "parent"},
 	}},
 	{Key: StructKey{Name: "syz_length_bytesize2_struct"}, Fields: []Type{
@@ -5140,8 +5140,8 @@ var structFields = []*StructFields{
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "seq_num"}},
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "ack_num"}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ns"}, TypeSize: 1, BitfieldLen: 1}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldLen: 3}},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 3}},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, ByteSize: 4, Buf: "parent"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "tcp_flags", FldName: "flags"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 8, 16, 32, 64, 128, 194}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "window_size"}, TypeSize: 2, BigEndian: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "tcp_packet", Protocol: 6},
@@ -5550,14 +5550,14 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "vlan_tag_ad"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 37120},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vlan_tag_q"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 33024},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vt_consize"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "rows"}, TypeSize: 2}},
diff --git a/sys/sys_ppc64le.go b/sys/sys_ppc64le.go
index fd6afb16c..c99c07297 100644
--- a/sys/sys_ppc64le.go
+++ b/sys/sys_ppc64le.go
@@ -482,11 +482,11 @@ var structFields = []*StructFields{
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "dst_port"}, TypeSize: 2, BigEndian: true}, ValuesStart: 20000, ValuesPerProc: 4},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "offset"}, TypeSize: 1}, ByteSize: 4, Buf: "parent"},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "cscov"}, TypeSize: 1, BitfieldLen: 4}, Val: 1},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ccval"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "parent", Protocol: 33},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "x"}, TypeSize: 1, BitfieldLen: 1}},
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldLen: 3}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "dccp_types", FldName: "type"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1, BitfieldOff: 5, BitfieldLen: 3, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "seq_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "ack_num"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
@@ -1488,9 +1488,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmp_ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "total_len"}, TypeSize: 2, BigEndian: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -1602,7 +1602,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "icmpv6_ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "length"}, TypeSize: 2, BigEndian: true}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2062,9 +2062,9 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv4_header"}, Fields: []Type{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "ihl"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 4},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ecn"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldLen: 6}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "dscp"}, TypeSize: 1, BitfieldOff: 2, BitfieldLen: 6, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "total_len"}, TypeSize: 2, BigEndian: true}, Buf: "ipv4_packet"},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "id"}, TypeSize: 2, BigEndian: true}, ValuesStart: 100, ValuesPerProc: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "frag_off"}, TypeSize: 2, BigEndian: true}},
@@ -2136,7 +2136,7 @@ var structFields = []*StructFields{
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 1}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "pointer"}, TypeSize: 1}},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_flags", FldName: "flg"}, TypeSize: 1, BitfieldLen: 4}, Vals: []uint64{0, 1, 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "oflw"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "timestamps"}, Type: &StructType{TypeCommon: TypeCommon{TypeName: "ipv4_option_timestamp_timestamp"}, IsPacked: true}},
 	}},
 	{Key: StructKey{Name: "ipv4_option_timestamp_timestamp"}, Fields: []Type{
@@ -2255,8 +2255,8 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved1"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_hi"}, TypeSize: 1}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "m_flag"}, TypeSize: 1, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldLen: 2}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldLen: 5}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "reserved2"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 2}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "fragment_off_lo"}, TypeSize: 1, BitfieldOff: 3, BitfieldLen: 5, BitfieldLst: true}},
 		&ProcType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "proc", FldName: "identification"}, TypeSize: 4}, ValuesStart: 100, ValuesPerProc: 4},
 	}},
 	{Key: StructKey{Name: "ipv6_hopots_ext_header"}, Fields: []Type{
@@ -2275,7 +2275,7 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "ipv6_packet"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "priority"}, TypeSize: 1, BitfieldLen: 4}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldLen: 4}, Val: 6},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "version"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, Val: 6},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "flow_label"}, Kind: 1, RangeBegin: 3, RangeEnd: 3},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "length"}, TypeSize: 2, BigEndian: true}, Buf: "payload"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "ipv6_types", FldName: "next_header"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 6, 8, 12, 17, 22, 29, 33, 41, 46, 47, 50, 51, 92, 94, 98, 103, 108, 132, 136, 137, 255, 0, 43, 44, 58, 59, 60, 135, 0, 43, 44, 47, 50, 51, 58, 59, 60, 135}},
@@ -2878,13 +2878,13 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "kvm_setup_opt_vmwrite"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "typ"}, TypeSize: 8}, Val: 8},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "sz"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldLen: 5}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldLen: 2}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldLen: 48}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fld"}, TypeSize: 8, BitfieldOff: 1, BitfieldLen: 5}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad0"}, TypeSize: 8, BitfieldOff: 6, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "ftyp"}, TypeSize: 8, BitfieldOff: 10, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad1"}, TypeSize: 8, BitfieldOff: 12, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "fsz"}, TypeSize: 8, BitfieldOff: 13, BitfieldLen: 2}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "pad2"}, TypeSize: 8, BitfieldOff: 15, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "val"}, TypeSize: 8, BitfieldOff: 16, BitfieldLen: 48, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "kvm_setup_opt_x86"}, Fields: []Type{
 		&StructType{TypeCommon: TypeCommon{TypeName: "kvm_setup_opt_cr0", FldName: "cr0"}},
@@ -4828,13 +4828,13 @@ var structFields = []*StructFields{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct0"}, Fields: []Type{
-		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10}, Vals: []uint64{0, 1, 2}},
+		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "syz_bf_flags", FldName: "f0"}, TypeSize: 2, BitfieldLen: 10, BitfieldLst: true}, Vals: []uint64{0, 1, 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int64", FldName: "f1"}, TypeSize: 8}},
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f2"}, TypeSize: 2, BitfieldLen: 5}, Val: 66},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldLen: 6}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15}, Val: 66},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11}, Buf: "parent"},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BigEndian: true, BitfieldLen: 11}, Buf: "parent"},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f3"}, TypeSize: 2, BitfieldOff: 5, BitfieldLen: 6, BitfieldLst: true}},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "f4"}, TypeSize: 4, BitfieldLen: 15, BitfieldLst: true}, Val: 66},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f5"}, TypeSize: 2, BitfieldLen: 11, BitfieldLst: true}, Buf: "parent"},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f6"}, TypeSize: 2, BitfieldLen: 11, BigEndian: true, BitfieldLst: true}, Buf: "parent"},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f7"}, TypeSize: 1}},
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1"}, Fields: []Type{
@@ -4843,15 +4843,15 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_bf_struct1_internal"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "syz_csum_encode"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "f0"}, TypeSize: 2}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "f1"}, TypeSize: 2, BigEndian: true}},
 		&ArrayType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f2"}, Type: &IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32"}, TypeSize: 4}}, Kind: 1, RangeEnd: 4},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f3"}, TypeSize: 1, BitfieldLen: 4}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldLen: 4}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "f4"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}},
 		&BufferType{TypeCommon: TypeCommon{TypeName: "array", FldName: "f5"}, Kind: 1, RangeBegin: 4, RangeEnd: 4},
 	}},
 	{Key: StructKey{Name: "syz_csum_icmp_packet"}, Fields: []Type{
@@ -4925,12 +4925,12 @@ var structFields = []*StructFields{
 	}},
 	{Key: StructKey{Name: "syz_length_bf_struct_inner"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f0"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldLen: 10}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f1"}, TypeSize: 4, BitfieldOff: 10, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f2"}, TypeSize: 4, BitfieldOff: 20, BitfieldLen: 10, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f3"}, TypeSize: 4, BitfieldLen: 32, BitfieldLst: true}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f4"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldLen: 16}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f5"}, TypeSize: 4, BitfieldOff: 16, BitfieldLen: 16, BitfieldLst: true}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int32", FldName: "f6"}, TypeSize: 4, BitfieldLen: 10, BitfieldLst: true}},
 		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "len", FldName: "f7"}, TypeSize: 4}, Buf: "parent"},
 	}},
 	{Key: StructKey{Name: "syz_length_bytesize2_struct"}, Fields: []Type{
@@ -5140,8 +5140,8 @@ var structFields = []*StructFields{
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "seq_num"}},
 		&ResourceType{TypeCommon: TypeCommon{TypeName: "tcp_seq_num", FldName: "ack_num"}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int8", FldName: "ns"}, TypeSize: 1, BitfieldLen: 1}},
-		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldLen: 3}},
-		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldLen: 4}, ByteSize: 4, Buf: "parent"},
+		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "reserved"}, TypeSize: 1, BitfieldOff: 1, BitfieldLen: 3}},
+		&LenType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "bytesize4", FldName: "data_off"}, TypeSize: 1, BitfieldOff: 4, BitfieldLen: 4, BitfieldLst: true}, ByteSize: 4, Buf: "parent"},
 		&FlagsType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "tcp_flags", FldName: "flags"}, TypeSize: 1}, Vals: []uint64{0, 1, 2, 4, 8, 16, 32, 64, 128, 194}},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16be", FldName: "window_size"}, TypeSize: 2, BigEndian: true}},
 		&CsumType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "csum", FldName: "csum"}, TypeSize: 2, BigEndian: true}, Kind: 1, Buf: "tcp_packet", Protocol: 6},
@@ -5550,14 +5550,14 @@ var structFields = []*StructFields{
 	{Key: StructKey{Name: "vlan_tag_ad"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 37120},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vlan_tag_q"}, Fields: []Type{
 		&ConstType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "const", FldName: "tpid"}, TypeSize: 2, BigEndian: true}, Val: 33024},
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "pcp"}, TypeSize: 2, BitfieldLen: 3}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldLen: 1}},
-		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldLen: 12}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "dei"}, TypeSize: 2, BitfieldOff: 3, BitfieldLen: 1}},
+		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "vid"}, TypeSize: 2, BitfieldOff: 4, BitfieldLen: 12, BitfieldLst: true}},
 	}},
 	{Key: StructKey{Name: "vt_consize"}, Fields: []Type{
 		&IntType{IntTypeCommon: IntTypeCommon{TypeCommon: TypeCommon{TypeName: "int16", FldName: "rows"}, TypeSize: 2}},