cmd/compile, cmd/link: stop generating unused go.string.hdr symbols.

name       old s/op    new s/op    delta
LinkCmdGo   0.29 ± 5%   0.29 ± 8%  -2.60%   (p=0.000 n=97+98)

name       old MaxRSS  new MaxRSS  delta
LinkCmdGo   106k ± 4%   105k ± 3%  -1.00%  (p=0.000 n=100+99)

Change-Id: I75a1c3b24ea711a15a5d2eae026b70b97ee7bad4
Reviewed-on: https://go-review.googlesource.com/31030
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>

diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index cb9ea52b62cdeac418697cfd7e90acb42aec49a7..1c4851795514df8f6728bc55be23dcec6ab36e87 100644 (file)
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -280,18 +280,7 @@ func dbvec(s *Sym, off int, bv bvec) int {
        return off
 }
 
-// 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) {
+func stringsym(s string) (data *obj.LSym) {
        var symname string
        if len(s) > 100 {
                // Huge strings are hashed to avoid long names in object files.
@@ -308,33 +297,15 @@ func stringsym(s string) (hdr, data *obj.LSym) {
        const prefix = "go.string."
        symdataname := prefix + symname
 
-       // 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
-       }
-
-       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 = 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
-       off = dsnameLSym(symdata, 0, s)
-       ggloblLSym(symdata, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
+       if !symdata.Seenglobl {
+               // string data
+               off := dsnameLSym(symdata, 0, s)
+               ggloblLSym(symdata, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
+       }
 
-       return symhdr, symdata
+       return symdata
 }
 
 var slicebytes_gen int
@@ -357,14 +328,6 @@ func slicebytes(nam *Node, s string, len int) {
        duintxx(nam.Sym, off, uint64(len), Widthint)
 }
 
-func datagostring(sval string, a *obj.Addr) {
-       symhdr, _ := stringsym(sval)
-       a.Type = obj.TYPE_MEM
-       a.Name = obj.NAME_EXTERN
-       a.Sym = symhdr
-       a.Offset = 0
-}
-
 func dsname(s *Sym, off int, t string) int {
        return dsnameLSym(Linksym(s), off, t)
 }
@@ -465,7 +428,7 @@ func gdatacomplex(nam *Node, cval *Mpcplx) {
 
 func gdatastring(nam *Node, sval string) {
        s := Linksym(nam.Sym)
-       _, symdata := stringsym(sval)
+       symdata := stringsym(sval)
        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/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 452d449f2130c9025c50faf216e0c7ce2ed31125..45070c8d310690f2d19413726da7dc6a54d279c1 100644 (file)
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -4525,7 +4525,7 @@ func (s *ssaExport) TypeBytePtr() ssa.Type { return ptrto(Types[TUINT8]) }
 // is the data component of a global string constant containing s.
 func (*ssaExport) StringData(s string) interface{} {
        // TODO: is idealstring correct?  It might not matter...
-       _, data := stringsym(s)
+       data := stringsym(s)
        return &ssa.ExternSymbol{Typ: idealstring, Sym: data}
 }
 

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index fecd71f674fb8723e850a8e5d299d1b51198f8e3..46d249f88a39edac1a6b426528db5daac756ba71 100644 (file)
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -393,7 +393,6 @@ const (
        STYPE
        SSTRING
        SGOSTRING
-       SGOSTRINGHDR
        SGOFUNC
        SGCBITS
        SRODATA
@@ -417,7 +416,6 @@ const (
        STYPERELRO
        SSTRINGRELRO
        SGOSTRINGRELRO
-       SGOSTRINGHDRRELRO
        SGOFUNCRELRO
        SGCBITSRELRO
        SRODATARELRO
@@ -466,7 +464,6 @@ var ReadOnly = []SymKind{
        STYPE,
        SSTRING,
        SGOSTRING,
-       SGOSTRINGHDR,
        SGOFUNC,
        SGCBITS,
        SRODATA,
@@ -476,14 +473,13 @@ var ReadOnly = []SymKind{
 // RelROMap describes the transformation of read-only symbols to rel-ro
 // symbols.
 var RelROMap = map[SymKind]SymKind{
-       STYPE:        STYPERELRO,
-       SSTRING:      SSTRINGRELRO,
-       SGOSTRING:    SGOSTRINGRELRO,
-       SGOSTRINGHDR: SGOSTRINGHDRRELRO,
-       SGOFUNC:      SGOFUNCRELRO,
-       SGCBITS:      SGCBITSRELRO,
-       SRODATA:      SRODATARELRO,
-       SFUNCTAB:     SFUNCTABRELRO,
+       STYPE:     STYPERELRO,
+       SSTRING:   SSTRINGRELRO,
+       SGOSTRING: SGOSTRINGRELRO,
+       SGOFUNC:   SGOFUNCRELRO,
+       SGCBITS:   SGCBITSRELRO,
+       SRODATA:   SRODATARELRO,
+       SFUNCTAB:  SFUNCTABRELRO,
 }
 
 type Reloc struct {

diff --git a/src/cmd/internal/obj/symkind_string.go b/src/cmd/internal/obj/symkind_string.go
index e8fed78841081eb4b2b3965b66ba4fa172fae33f..fef8c355e45025e2c761c3bc385520bda1530923 100644 (file)
--- a/src/cmd/internal/obj/symkind_string.go
+++ b/src/cmd/internal/obj/symkind_string.go
@@ -4,9 +4,9 @@ package obj
 
 import "fmt"
 
-const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOSTRINGHDRSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSMACHOPLTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOSTRINGHDRRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILESFILEPATHSCONSTSDYNIMPORTSHOSTOBJSDWARFSECTSDWARFINFO"
+const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSMACHOPLTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILESFILEPATHSCONSTSDYNIMPORTSHOSTOBJSDWARFSECTSDWARFINFO"
 
-var _SymKind_index = [...]uint16{0, 4, 9, 19, 24, 31, 40, 52, 59, 66, 73, 81, 91, 100, 110, 122, 136, 153, 165, 177, 189, 202, 211, 220, 227, 235, 243, 249, 258, 266, 273, 283, 291, 296, 300, 309, 316, 321, 333, 345, 362, 379, 384, 393, 399, 409, 417, 427, 437}
+var _SymKind_index = [...]uint16{0, 4, 9, 19, 24, 31, 40, 47, 54, 61, 69, 79, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 214, 220, 229, 237, 244, 254, 262, 267, 271, 280, 287, 292, 304, 316, 333, 350, 355, 364, 370, 380, 388, 398, 408}
 
 func (i SymKind) String() string {
        if i < 0 || i >= SymKind(len(_SymKind_index)-1) {

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index 4714d20866e348be7251f82ffe9d2d5cd93a36e3..5460b76c99f4aa32293b6e64957f1ffbdf1f531d 100644 (file)
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -1135,7 +1135,7 @@ func symalign(s *Symbol) int32 {
        } else if s.Align != 0 {
                return min
        }
-       if (strings.HasPrefix(s.Name, "go.string.") && !strings.HasPrefix(s.Name, "go.string.hdr.")) || strings.HasPrefix(s.Name, "type..namedata.") {
+       if strings.HasPrefix(s.Name, "go.string.") || strings.HasPrefix(s.Name, "type..namedata.") {
                // String data is just bytes.
                // If we align it, we waste a lot of space to padding.
                return min
@@ -1336,7 +1336,7 @@ func (ctxt *Link) dodata() {
                        for _, s := range data[symnro] {
                                isRelro := len(s.R) > 0
                                switch s.Type {
-                               case obj.STYPE, obj.SGOSTRINGHDR, obj.STYPERELRO, obj.SGOSTRINGHDRRELRO, obj.SGOFUNCRELRO:
+                               case obj.STYPE, obj.STYPERELRO, obj.SGOFUNCRELRO:
                                        // Symbols are not sorted yet, so it is possible
                                        // that an Outer symbol has been changed to a
                                        // relro Type before it reaches here.

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 735408cd4740c0ed0dde20a808025e61906bfd81..629facdc45d4adba3d501663d98c243b1147e0e1 100644 (file)
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1890,13 +1890,11 @@ func genasmsym(ctxt *Link, put func(*Link, *Symbol, string, SymbolType, int64, *
                        obj.STYPE,
                        obj.SSTRING,
                        obj.SGOSTRING,
-                       obj.SGOSTRINGHDR,
                        obj.SGOFUNC,
                        obj.SGCBITS,
                        obj.STYPERELRO,
                        obj.SSTRINGRELRO,
                        obj.SGOSTRINGRELRO,
-                       obj.SGOSTRINGHDRRELRO,
                        obj.SGOFUNCRELRO,
                        obj.SGCBITSRELRO,
                        obj.SRODATARELRO,

diff --git a/src/cmd/link/internal/ld/symtab.go b/src/cmd/link/internal/ld/symtab.go
index e4280f0ccbcbee4ed92a18a8f56eabb2588ad1fb..97c6c2db72f3464a336116b387e21c300acbc8a7 100644 (file)
--- a/src/cmd/link/internal/ld/symtab.go
+++ b/src/cmd/link/internal/ld/symtab.go
@@ -435,10 +435,9 @@ func (ctxt *Link) symtab() {
                return s
        }
        var (
-               symgostring    = groupSym("go.string.*", obj.SGOSTRING)
-               symgostringhdr = groupSym("go.string.hdr.*", obj.SGOSTRINGHDR)
-               symgofunc      = groupSym("go.func.*", obj.SGOFUNC)
-               symgcbits      = groupSym("runtime.gcbits.*", obj.SGCBITS)
+               symgostring = groupSym("go.string.*", obj.SGOSTRING)
+               symgofunc   = groupSym("go.func.*", obj.SGOFUNC)
+               symgcbits   = groupSym("runtime.gcbits.*", obj.SGCBITS)
        )
 
        var symgofuncrel *Symbol
@@ -508,10 +507,6 @@ func (ctxt *Link) symtab() {
                        s.Type = obj.SGOSTRING
                        s.Attr |= AttrHidden
                        s.Outer = symgostring
-                       if strings.HasPrefix(s.Name, "go.string.hdr.") {
-                               s.Type = obj.SGOSTRINGHDR
-                               s.Outer = symgostringhdr
-                       }
 
                case strings.HasPrefix(s.Name, "runtime.gcbits."):
                        s.Type = obj.SGCBITS