1 files changed, 47 insertions, 61 deletions

diff --git a/pkg/compiler/gen.go b/pkg/compiler/gen.go
index 6ba312d3c..ff9cb51e2 100644
--- a/pkg/compiler/gen.go
+++ b/pkg/compiler/gen.go
@@ -199,9 +199,8 @@ func (ctx *structGen) walkStruct(t *prog.StructType) {
 			varlen = true
 		}
 	}
-	comp.markBitfields(t.Fields)
 	packed, sizeAttr, alignAttr := comp.parseStructAttrs(structNode)
-	t.Fields = comp.addAlignment(t.Fields, varlen, packed, alignAttr)
+	t.Fields = comp.layoutStruct(t.Fields, varlen, packed, alignAttr)
 	t.AlignAttr = alignAttr
 	t.TypeSize = 0
 	if !varlen {
@@ -259,79 +258,44 @@ func (comp *compiler) genStructDesc(res *prog.StructDesc, n *ast.Struct, dir pro
 	}
 }
 
-func (comp *compiler) markBitfields(fields []prog.Type) {
-	var bfOffset uint64
-	for i, f := range fields {
-		if f.BitfieldLength() == 0 {
-			continue
-		}
-		off, middle := bfOffset, true
-		bfOffset += f.BitfieldLength()
-		if i == len(fields)-1 || // Last bitfield in a group, if last field of the struct...
-			fields[i+1].BitfieldLength() == 0 || // or next field is not a bitfield...
-			f.Size() != fields[i+1].Size() || // or next field is of different size...
-			bfOffset+fields[i+1].BitfieldLength() > f.Size()*8 { // or next field does not fit into the current group.
-			middle, bfOffset = false, 0
-		}
-		setBitfieldOffset(f, off, middle)
-	}
-}
-
-func setBitfieldOffset(t0 prog.Type, offset uint64, middle bool) {
-	size := t0.Size()
-	unit := size
-	if middle {
-		size = 0
-	}
-	switch t := t0.(type) {
-	case *prog.IntType:
-		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
-	case *prog.ConstType:
-		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
-	case *prog.LenType:
-		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
-	case *prog.FlagsType:
-		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
-	case *prog.ProcType:
-		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
-	default:
-		panic(fmt.Sprintf("type %#v can't be a bitfield", t))
-	}
-}
-
-func (comp *compiler) addAlignment(fields []prog.Type, varlen, packed bool, alignAttr uint64) []prog.Type {
+func (comp *compiler) layoutStruct(fields []prog.Type, varlen, packed bool, alignAttr uint64) []prog.Type {
 	var newFields []prog.Type
-	if packed {
-		// If a struct is packed, statically sized and has explicitly set alignment,
-		// add a padding at the end.
-		newFields = fields
-		if !varlen && alignAttr != 0 {
-			size := uint64(0)
-			for _, f := range fields {
-				size += f.Size()
-			}
-			if tail := size % alignAttr; tail != 0 {
-				newFields = append(newFields, genPad(alignAttr-tail))
+	var align, off, bfOffset uint64
+	for i, f := range fields {
+		if f.IsBitfield() {
+			off, middle := bfOffset, true
+			bfOffset += f.BitfieldLength()
+			// Last bitfield in a group, if last field of the struct...
+			if i == len(fields)-1 ||
+				// or next field is not a bitfield...
+				fields[i+1].BitfieldLength() == 0 ||
+				// or next field is of different size...
+				f.Size() != fields[i+1].Size() ||
+				// or next field does not fit into the current group.
+				bfOffset+fields[i+1].BitfieldLength() > f.Size()*8 {
+				middle, bfOffset = false, 0
 			}
+			setBitfieldOffset(f, off, middle)
 		}
-		return newFields
-	}
-	var align, off uint64
-	for i, f := range fields {
-		if i == 0 || fields[i-1].Size() != 0 {
+		needPadding := true
+		if i != 0 {
+			prev := fields[i-1]
+			needPadding = !prev.Varlen() && prev.Size() != 0
+		}
+		if needPadding && !packed {
 			a := comp.typeAlign(f)
 			if align < a {
 				align = a
 			}
 			// Append padding if the last field is not a bitfield or it's the last bitfield in a set.
-			if off%a != 0 {
+			if !packed && off%a != 0 {
 				pad := a - off%a
 				off += pad
 				newFields = append(newFields, genPad(pad))
 			}
 		}
 		newFields = append(newFields, f)
-		if !(i == len(fields)-1 && f.Varlen()) {
+		if !f.Varlen() {
 			// Increase offset if the current field except when it's
 			// the last field in a struct and has variable length.
 			off += f.Size()
@@ -348,6 +312,28 @@ func (comp *compiler) addAlignment(fields []prog.Type, varlen, packed bool, alig
 	return newFields
 }
 
+func setBitfieldOffset(t0 prog.Type, offset uint64, middle bool) {
+	size := t0.Size()
+	unit := size
+	if middle {
+		size = 0
+	}
+	switch t := t0.(type) {
+	case *prog.IntType:
+		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
+	case *prog.ConstType:
+		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
+	case *prog.LenType:
+		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
+	case *prog.FlagsType:
+		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
+	case *prog.ProcType:
+		t.BitfieldOff, t.BitfieldUnit, t.TypeSize = offset, unit, size
+	default:
+		panic(fmt.Sprintf("type %#v can't be a bitfield", t))
+	}
+}
+
 func (comp *compiler) typeAlign(t0 prog.Type) uint64 {
 	switch t := t0.(type) {
 	case *prog.IntType, *prog.LenType, *prog.FlagsType, *prog.ProcType,