cmd/compile: don't create 2 Sym's and 2 Node's for every string
For every string constant the compiler was creating 2 Sym's and 2
Node's. It would never refer to them again, but would keep them alive
in gostringpkg. This changes the code to just use obj.LSym's instead.
When compiling x/tools/go/types, this yields about a 15% reduction in
the number of calls to newname and a 3% reduction in the total number of
Node objects. Unfortunately I couldn't see any change in compile time,
but reducing memory usage is desirable anyhow.
Passes toolstash -cmp.
Change-Id: I24f1cb1e6cff0a3afba4ca66f7166874917a036b
Reviewed-on: https://go-review.googlesource.com/20792
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go
index 4473ee6..6feb5fb 100644
--- a/src/cmd/compile/internal/gc/go.go
+++ b/src/cmd/compile/internal/gc/go.go
@@ -249,8 +249,6 @@
var importpkg *Pkg // package being imported
-var gostringpkg *Pkg // fake pkg for Go strings
-
var itabpkg *Pkg // fake pkg for itab cache
var Runtimepkg *Pkg // package runtime
diff --git a/src/cmd/compile/internal/gc/gsubr.go b/src/cmd/compile/internal/gc/gsubr.go
index efc48c7..ddaa3f2 100644
--- a/src/cmd/compile/internal/gc/gsubr.go
+++ b/src/cmd/compile/internal/gc/gsubr.go
@@ -234,10 +234,14 @@
}
func ggloblsym(s *Sym, width int32, flags int16) {
+ ggloblLSym(Linksym(s), width, flags)
+}
+
+func ggloblLSym(s *obj.LSym, width int32, flags int16) {
p := Thearch.Gins(obj.AGLOBL, nil, nil)
p.From.Type = obj.TYPE_MEM
p.From.Name = obj.NAME_EXTERN
- p.From.Sym = Linksym(s)
+ p.From.Sym = s
if flags&obj.LOCAL != 0 {
p.From.Sym.Local = true
flags &= ^obj.LOCAL
diff --git a/src/cmd/compile/internal/gc/main.go b/src/cmd/compile/internal/gc/main.go
index f4396d1..63a0ab8 100644
--- a/src/cmd/compile/internal/gc/main.go
+++ b/src/cmd/compile/internal/gc/main.go
@@ -122,11 +122,6 @@
Runtimepkg.Name = "runtime"
// pseudo-packages used in symbol tables
- gostringpkg = mkpkg("go.string")
-
- gostringpkg.Name = "go.string"
- gostringpkg.Prefix = "go.string" // not go%2estring
-
itabpkg = mkpkg("go.itab")
itabpkg.Name = "go.itab"
diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index 91d0ac8..6093d4a 100644
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -159,12 +159,16 @@
}
func duintxx(s *Sym, off int, v uint64, wid int) int {
+ return duintxxLSym(Linksym(s), off, v, wid)
+}
+
+func duintxxLSym(s *obj.LSym, off int, v uint64, wid int) int {
// Update symbol data directly instead of generating a
// DATA instruction that liblink will have to interpret later.
// This reduces compilation time and memory usage.
off = int(Rnd(int64(off), int64(wid)))
- return int(obj.Setuintxx(Ctxt, Linksym(s), int64(off), v, int64(wid)))
+ return int(obj.Setuintxx(Ctxt, s, int64(off), v, int64(wid)))
}
func duint8(s *Sym, off int, v uint8) int {
@@ -183,7 +187,18 @@
return duintxx(s, off, v, Widthptr)
}
-func stringsym(s string) (hdr, data *Sym) {
+// stringConstantSyms holds the pair of symbols we create for a
+// constant string.
+type stringConstantSyms struct {
+ hdr *obj.LSym // string header
+ data *obj.LSym // actual string data
+}
+
+// stringConstants maps from the symbol name we use for the string
+// contents to the pair of linker symbols for that string.
+var stringConstants = make(map[string]stringConstantSyms, 100)
+
+func stringsym(s string) (hdr, data *obj.LSym) {
var symname string
if len(s) > 100 {
// Huge strings are hashed to avoid long names in object files.
@@ -197,31 +212,34 @@
symname = strconv.Quote(s)
}
- symhdr := Pkglookup("hdr."+symname, gostringpkg)
- symdata := Pkglookup(symname, gostringpkg)
+ const prefix = "go.string."
+ symdataname := prefix + symname
- // SymUniq flag indicates that data is generated already
- if symhdr.Flags&SymUniq != 0 {
- return symhdr, symdata
+ // All the strings have the same prefix, so ignore it for map
+ // purposes, but use a slice of the symbol name string to
+ // reduce long-term memory overhead.
+ key := symdataname[len(prefix):]
+
+ if syms, ok := stringConstants[key]; ok {
+ return syms.hdr, syms.data
}
- symhdr.Flags |= SymUniq
- symhdr.Def = newname(symhdr)
+
+ symhdrname := "go.string.hdr." + symname
+
+ symhdr := obj.Linklookup(Ctxt, symhdrname, 0)
+ symdata := obj.Linklookup(Ctxt, symdataname, 0)
+
+ stringConstants[key] = stringConstantSyms{symhdr, symdata}
// string header
off := 0
- off = dsymptr(symhdr, off, symdata, 0)
- off = duintxx(symhdr, off, uint64(len(s)), Widthint)
- ggloblsym(symhdr, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
+ off = dsymptrLSym(symhdr, off, symdata, 0)
+ off = duintxxLSym(symhdr, off, uint64(len(s)), Widthint)
+ ggloblLSym(symhdr, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
// string data
- if symdata.Flags&SymUniq != 0 {
- return symhdr, symdata
- }
- symdata.Flags |= SymUniq
- symdata.Def = newname(symdata)
-
- off = dsname(symdata, 0, s)
- ggloblsym(symdata, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
+ off = dsnameLSym(symdata, 0, s)
+ ggloblLSym(symdata, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
return symhdr, symdata
}
@@ -250,8 +268,7 @@
_, symdata := stringsym(s)
a.Type = obj.TYPE_MEM
a.Name = obj.NAME_EXTERN
- a.Sym = Linksym(symdata)
- a.Node = symdata.Def
+ a.Sym = symdata
a.Offset = 0
a.Etype = uint8(Simtype[TINT])
}
@@ -260,8 +277,7 @@
symhdr, _ := stringsym(sval)
a.Type = obj.TYPE_MEM
a.Name = obj.NAME_EXTERN
- a.Sym = Linksym(symhdr)
- a.Node = symhdr.Def
+ a.Sym = symhdr
a.Offset = 0
a.Etype = uint8(TSTRING)
}
@@ -279,19 +295,27 @@
}
off = int(Rnd(int64(off), int64(Widthptr)))
symhdr, _ := stringsym(*lit)
- Linksym(s).WriteAddr(Ctxt, int64(off), Widthptr, Linksym(symhdr), 0)
+ Linksym(s).WriteAddr(Ctxt, int64(off), Widthptr, symhdr, 0)
off += Widthptr
return off
}
func dsname(s *Sym, off int, t string) int {
- Linksym(s).WriteString(Ctxt, int64(off), len(t), t)
+ return dsnameLSym(Linksym(s), off, t)
+}
+
+func dsnameLSym(s *obj.LSym, off int, t string) int {
+ s.WriteString(Ctxt, int64(off), len(t), t)
return off + len(t)
}
func dsymptr(s *Sym, off int, x *Sym, xoff int) int {
+ return dsymptrLSym(Linksym(s), off, Linksym(x), xoff)
+}
+
+func dsymptrLSym(s *obj.LSym, off int, x *obj.LSym, xoff int) int {
off = int(Rnd(int64(off), int64(Widthptr)))
- Linksym(s).WriteAddr(Ctxt, int64(off), Widthptr, Linksym(x), int64(xoff))
+ s.WriteAddr(Ctxt, int64(off), Widthptr, x, int64(xoff))
off += Widthptr
return off
}
@@ -368,6 +392,6 @@
func gdatastring(nam *Node, sval string) {
s := Linksym(nam.Sym)
_, symdata := stringsym(sval)
- s.WriteAddr(Ctxt, nam.Xoffset, Widthptr, Linksym(symdata), 0)
+ s.WriteAddr(Ctxt, nam.Xoffset, Widthptr, symdata, 0)
s.WriteInt(Ctxt, nam.Xoffset+int64(Widthptr), Widthint, int64(len(sval)))
}
diff --git a/src/cmd/compile/internal/gc/reflect.go b/src/cmd/compile/internal/gc/reflect.go
index e72fa4f..a8d0c93 100644
--- a/src/cmd/compile/internal/gc/reflect.go
+++ b/src/cmd/compile/internal/gc/reflect.go
@@ -770,7 +770,7 @@
prefix = 1
}
_, symdata := stringsym(p) // string
- ot = dsymptr(s, ot, symdata, prefix)
+ ot = dsymptrLSym(Linksym(s), ot, symdata, prefix)
ot = duintxx(s, ot, uint64(len(p)-prefix), Widthint)
return ot
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 716be35..06e317e 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -3845,7 +3845,14 @@
switch sym := v.Aux.(type) {
case *ssa.ExternSymbol:
a.Name = obj.NAME_EXTERN
- a.Sym = Linksym(sym.Sym.(*Sym))
+ switch s := sym.Sym.(type) {
+ case *Sym:
+ a.Sym = Linksym(s)
+ case *obj.LSym:
+ a.Sym = s
+ default:
+ v.Fatalf("ExternSymbol.Sym is %T", s)
+ }
case *ssa.ArgSymbol:
n := sym.Node.(*Node)
a.Name = obj.NAME_PARAM
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 7da7ada..8cae125 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -343,6 +343,12 @@
R []Reloc
}
+// The compiler needs LSym to satisfy fmt.Stringer, because it stores
+// an LSym in ssa.ExternSymbol.
+func (s *LSym) String() string {
+ return s.Name
+}
+
type Pcln struct {
Pcsp Pcdata
Pcfile Pcdata
