cmd/internal/gc, cmd/internal/ld, cmd/internal/obj: teach compiler about local symbols

This lets us avoid loading string constants via the GOT and (together with
http://golang.org/cl/9102) results in the fannkuch benchmark having very similar
register usage with -dynlink as without.

Change-Id: Ic3892b399074982b76773c3e547cfbba5dabb6f9
Reviewed-on: https://go-review.googlesource.com/9103
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/6g/prog.go b/src/cmd/6g/prog.go
index 5aeaeaa4ed4f56db0e7c9a1f1c5875cab7bdd049..5f604742c37842124f854f5fea3b2bb52d46c048 100644 (file)
--- a/src/cmd/6g/prog.go
+++ b/src/cmd/6g/prog.go
@@ -299,7 +299,7 @@ func proginfo(p *obj.Prog) {
                if p.As == x86.ALEAQ || info.Flags == gc.Pseudo || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
                        return
                }
-               if p.As == obj.ADUFFZERO || p.As == obj.ADUFFCOPY || p.From.Name == obj.NAME_EXTERN || p.To.Name == obj.NAME_EXTERN {
+               if p.As == obj.ADUFFZERO || p.As == obj.ADUFFCOPY || (p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local) || (p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local) {
                        info.Reguse |= R15
                        info.Regset |= R15
                        return

diff --git a/src/cmd/internal/gc/gsubr.go b/src/cmd/internal/gc/gsubr.go
index 1f6b7d2ec6a70afbcddc641f6eb514cc62025937..53b3f6c41de6db2bb0a7af5d2262d1475c89ffb2 100644 (file)
--- a/src/cmd/internal/gc/gsubr.go
+++ b/src/cmd/internal/gc/gsubr.go
@@ -218,11 +218,15 @@ func ggloblnod(nam *Node) {
        }
 }
 
-func ggloblsym(s *Sym, width int32, flags int8) {
+func ggloblsym(s *Sym, 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)
+       if flags&obj.LOCAL != 0 {
+               p.From.Sym.Local = true
+               flags &= ^obj.LOCAL
+       }
        p.To.Type = obj.TYPE_CONST
        p.To.Offset = int64(width)
        p.From3.Offset = int64(flags)

diff --git a/src/cmd/internal/gc/obj.go b/src/cmd/internal/gc/obj.go
index 5885eb5d7e767b923c5cd0d072a399a4122a4006..891f5548f7f47ae7d16e3b687dc85dcc51a07936 100644 (file)
--- a/src/cmd/internal/gc/obj.go
+++ b/src/cmd/internal/gc/obj.go
@@ -245,7 +245,7 @@ func stringsym(s string) *Sym {
 
        off = duint8(sym, off, 0)                    // terminating NUL for runtime
        off = (off + Widthptr - 1) &^ (Widthptr - 1) // round to pointer alignment
-       ggloblsym(sym, int32(off), obj.DUPOK|obj.RODATA)
+       ggloblsym(sym, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
 
        return sym
 }
@@ -269,7 +269,7 @@ func slicebytes(nam *Node, s string, len int) {
                off = dsname(sym, off, s[n:n+m])
        }
 
-       ggloblsym(sym, int32(off), obj.NOPTR)
+       ggloblsym(sym, int32(off), obj.NOPTR|obj.LOCAL)
 
        if nam.Op != ONAME {
                Fatal("slicebytes %v", nam)

diff --git a/src/cmd/internal/gc/pgen.go b/src/cmd/internal/gc/pgen.go
index 5848f98af033f8b0839c729690e40b2506a52c5b..1667a5c13e629042fe602150adbd53e810b736ac 100644 (file)
--- a/src/cmd/internal/gc/pgen.go
+++ b/src/cmd/internal/gc/pgen.go
@@ -161,7 +161,7 @@ func emitptrargsmap() {
                }
        }
 
-       ggloblsym(sym, int32(off), obj.RODATA)
+       ggloblsym(sym, int32(off), obj.RODATA|obj.LOCAL)
 }
 
 // Sort the list of stack variables. Autos after anything else,

diff --git a/src/cmd/internal/gc/reflect.go b/src/cmd/internal/gc/reflect.go
index 47697befba0c85a9bfc6bd451b13e464767d4890..824ed0b4277f3d02eec7e7ac86d9876aa35ee536 100644 (file)
--- a/src/cmd/internal/gc/reflect.go
+++ b/src/cmd/internal/gc/reflect.go
@@ -814,7 +814,7 @@ func dcommontype(s *Sym, ot int, t *Type) int {
                        for i := 0; i < 2*Widthptr; i++ {
                                duint8(sbits, i, gcmask[i])
                        }
-                       ggloblsym(sbits, 2*int32(Widthptr), obj.DUPOK|obj.RODATA)
+                       ggloblsym(sbits, 2*int32(Widthptr), obj.DUPOK|obj.RODATA|obj.LOCAL)
                }
 
                ot = dsymptr(s, ot, sbits, 0)
@@ -1203,7 +1203,7 @@ ok:
        }
 
        ot = dextratype(s, ot, t, xt)
-       ggloblsym(s, int32(ot), int8(dupok|obj.RODATA))
+       ggloblsym(s, int32(ot), int16(dupok|obj.RODATA))
 
        // generate typelink.foo pointing at s = type.foo.
        // The linker will leave a table of all the typelinks for
@@ -1229,7 +1229,7 @@ ok:
                case TARRAY, TCHAN, TFUNC, TMAP:
                        slink := typelinksym(t)
                        dsymptr(slink, 0, s, 0)
-                       ggloblsym(slink, int32(Widthptr), int8(dupok|obj.RODATA))
+                       ggloblsym(slink, int32(Widthptr), int16(dupok|obj.RODATA))
                }
        }
 

diff --git a/src/cmd/internal/ld/objfile.go b/src/cmd/internal/ld/objfile.go
index 1e45d72fd8b009c84819e9f6a96b061425147b44..41534c857c54eccd2d1d2b22524c2df01316621f 100644 (file)
--- a/src/cmd/internal/ld/objfile.go
+++ b/src/cmd/internal/ld/objfile.go
@@ -72,8 +72,12 @@ func readsym(ctxt *Link, f *Biobuf, pkg string, pn string) {
        if v != 0 && v != 1 {
                log.Fatalf("invalid symbol version %d", v)
        }
-       dupok := int(rdint(f))
-       dupok &= 1
+       flags := int(rdint(f))
+       dupok := flags & 1
+       local := false
+       if flags&2 != 0 {
+               local = true
+       }
        size := int(rdint(f))
        typ := rdsym(ctxt, f, pkg)
        var data []byte
@@ -125,6 +129,7 @@ overwrite:
        if s.Size < int64(size) {
                s.Size = int64(size)
        }
+       s.Local = local
        if typ != nil { // if bss sym defined multiple times, take type from any one def
                s.Gotype = typ
        }

diff --git a/src/cmd/internal/ld/symtab.go b/src/cmd/internal/ld/symtab.go
index 4d57d87c49ac38b3789d188b2c5731de8a4a0fd4..31baba010b265b5cea6c060dacc37c0c0d2c6300 100644 (file)
--- a/src/cmd/internal/ld/symtab.go
+++ b/src/cmd/internal/ld/symtab.go
@@ -373,15 +373,7 @@ func symtab() {
        // just defined above will be first.
        // hide the specific symbols.
        for s := Ctxt.Allsym; s != nil; s = s.Allsym {
-               if !s.Reachable || s.Special != 0 {
-                       continue
-               }
-
-               if strings.Contains(s.Name, "..gostring.") || strings.Contains(s.Name, "..gobytes.") {
-                       s.Local = true
-               }
-
-               if s.Type != obj.SRODATA {
+               if !s.Reachable || s.Special != 0 || s.Type != obj.SRODATA {
                        continue
                }
 

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 33b28580eaadf13fa10e2061cd94cd56088eb332..39f8941779be49f352b07e6b873c5f684f9a6625 100644 (file)
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -273,6 +273,7 @@ const (
        A_ARCHSPECIFIC
 )
 
+// An LSym is the sort of symbol that is written to an object file.
 type LSym struct {
        Name      string
        Type      int16
@@ -283,18 +284,25 @@ type LSym struct {
        Leaf      uint8
        Seenglobl uint8
        Onlist    uint8
-       Args      int32
-       Locals    int32
-       Value     int64
-       Size      int64
-       Next      *LSym
-       Gotype    *LSym
-       Autom     *Auto
-       Text      *Prog
-       Etext     *Prog
-       Pcln      *Pcln
-       P         []byte
-       R         []Reloc
+       // Local means make the symbol local even when compiling Go code to reference Go
+       // symbols in other shared libraries, as in this mode symbols are global by
+       // default. "local" here means in the sense of the dynamic linker, i.e. not
+       // visible outside of the module (shared library or executable) that contains its
+       // definition. (When not compiling to support Go shared libraries, all symbols are
+       // local in this sense unless there is a cgo_export_* directive).
+       Local  bool
+       Args   int32
+       Locals int32
+       Value  int64
+       Size   int64
+       Next   *LSym
+       Gotype *LSym
+       Autom  *Auto
+       Text   *Prog
+       Etext  *Prog
+       Pcln   *Pcln
+       P      []byte
+       R      []Reloc
 }
 
 type Pcln struct {

diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index 62426a5d7304d72bae610ebcd95096b2f469bb95..473a4bffe21f20743fc2c041813f511824e113cc 100644 (file)
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -400,7 +400,11 @@ func writesym(ctxt *Link, b *Biobuf, s *LSym) {
        wrint(b, int64(s.Type))
        wrstring(b, s.Name)
        wrint(b, int64(s.Version))
-       wrint(b, int64(s.Dupok))
+       flags := int64(s.Dupok)
+       if s.Local {
+               flags |= 2
+       }
+       wrint(b, flags)
        wrint(b, s.Size)
        wrsym(b, s.Gotype)
        wrdata(b, s.P)

diff --git a/src/cmd/internal/obj/textflag.go b/src/cmd/internal/obj/textflag.go
index e0e641da9bb7542ba9211501960b1284e7d5d803..b5d27a60ee18c4a5904ff776db4a20d944363a54 100644 (file)
--- a/src/cmd/internal/obj/textflag.go
+++ b/src/cmd/internal/obj/textflag.go
@@ -30,4 +30,7 @@ const (
 
        // This function uses its incoming context register.
        NEEDCTXT = 64
+
+       // When passed to ggloblsym, causes Local to be set to true on the LSym it creates.
+       LOCAL = 128
 )

diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index d4c10e61cb8b8e1bc4d0d47104232d8570eafc7b..e70bdca9df205d87b779e144397f70c4fcf29736 100644 (file)
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -251,6 +251,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
                        p.From.Type = obj.TYPE_MEM
                        p.From.Name = obj.NAME_EXTERN
                        p.From.Sym = s
+                       p.From.Sym.Local = true
                        p.From.Offset = 0
                }
 
@@ -294,6 +295,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
                        p.From.Type = obj.TYPE_MEM
                        p.From.Name = obj.NAME_EXTERN
                        p.From.Sym = s
+                       p.From.Sym.Local = true
                        p.From.Offset = 0
                }
        }
@@ -327,11 +329,11 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
        }
 
        if ctxt.Flag_dynlink {
-               if p.As == ALEAQ && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN {
+               if p.As == ALEAQ && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
                        p.As = AMOVQ
                        p.From.Type = obj.TYPE_ADDR
                }
-               if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN {
+               if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
                        if p.As != AMOVQ {
                                ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
                        }
@@ -356,12 +358,12 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
                        ctxt.Diag("don't know how to handle %v with -dynlink", p)
                }
                var source *obj.Addr
-               if p.From.Name == obj.NAME_EXTERN {
-                       if p.To.Name == obj.NAME_EXTERN {
+               if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
+                       if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
                                ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
                        }
                        source = &p.From
-               } else if p.To.Name == obj.NAME_EXTERN {
+               } else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
                        source = &p.To
                } else {
                        return