pkg/compiler: deduplicate Types in descriptions

Add prog.Ref Type that serves as a proxy for real types
and allows to deduplicate Types in generated descriptions.
The Ref type is effectively an index in an array of types.
Just before serialization pkg/compiler replaces real types
with the Ref types and prepares corresponding array of real types.
When a Target is registered in prog package, we do the opposite
operation and replace Ref's with the corresponding real types.

This brings improvements across the board:
compiler memory consumption is reduced by 15%,
test building time by 25%, descriptions size by 33%.

Before:
$ du -h sys/linux/gen
54M	sys/linux/gen

$ time GOMAXPROCS=1 go test -p=1 -c ./prog
real	0m54.200s
real	0m53.883s

$ time GOMAXPROCS=1 go install -p=1 ./tools/syz-execprog
real	0m27.911s
real	0m27.767s

$ TIME="%e %P %M" GOMAXPROCS=1 time go tool compile ./sys/linux/gen
20.59 100% 3200016
20.97 100% 3445976
20.25 100% 3209684

After:
$ du -h sys/linux/gen
36M	sys/linux/gen

$ time GOMAXPROCS=1 go test -p=1 -c ./prog
real	0m42.290s
real	0m43.230s

$ time GOMAXPROCS=1 go install -p=1 ./tools/syz-execprog
real	0m24.337s
real	0m24.727s

$ TIME="%e %P %M" GOMAXPROCS=1 time go tool compile ./sys/linux/gen
19.11 100% 2764952
19.66 100% 2787624
19.35 100% 2749376

Update #1580

1 files changed, 6 insertions, 2 deletions

diff --git a/sys/syz-sysgen/sysgen.go b/sys/syz-sysgen/sysgen.go
index 8043adf9d..a424e1488 100644
--- a/sys/syz-sysgen/sysgen.go
+++ b/sys/syz-sysgen/sysgen.go
@@ -205,11 +205,11 @@ func generate(target *targets.Target, prg *compiler.Prog, consts map[string]uint
 	fmt.Fprintf(out, "\tRegisterTarget(&Target{"+
 		"OS: %q, Arch: %q, Revision: revision_%v, PtrSize: %v, "+
 		"PageSize: %v, NumPages: %v, DataOffset: %v, Syscalls: syscalls_%v, "+
-		"Resources: resources_%v, Structs: structDescs_%v, Consts: consts_%v}, "+
+		"Resources: resources_%v, Structs: structDescs_%v, Types: types_%v, Consts: consts_%v}, "+
 		"InitTarget)\n}\n\n",
 		target.OS, target.Arch, target.Arch, target.PtrSize,
 		target.PageSize, target.NumPages, target.DataOffset,
-		target.Arch, target.Arch, target.Arch, target.Arch)
+		target.Arch, target.Arch, target.Arch, target.Arch, target.Arch)
 
 	fmt.Fprintf(out, "var resources_%v = ", target.Arch)
 	serializer.Write(out, prg.Resources)
@@ -223,6 +223,10 @@ func generate(target *targets.Target, prg *compiler.Prog, consts map[string]uint
 	serializer.Write(out, prg.Syscalls)
 	fmt.Fprintf(out, "\n\n")
 
+	fmt.Fprintf(out, "var types_%v = ", target.Arch)
+	serializer.Write(out, prg.Types)
+	fmt.Fprintf(out, "\n\n")
+
 	constArr := make([]prog.ConstValue, 0, len(consts))
 	for name, val := range consts {
 		constArr = append(constArr, prog.ConstValue{Name: name, Value: val})