cmd/compile: remove isStmt symbol from FuncInfo

As promised in CL 188238, removing the obsolete symbol.

Here are the latest stats. This is baselined at "e53edafb" with only
these changes applied, run on magna.cam. The linker looks straight
better (in memory and speed).

There is still a change I'm working on walking the progs to generate the
debug_lines data in the compiler. That will likely result in a compiler
speedup.

name                      old time/op       new time/op       delta
Template                        324ms ± 3%        317ms ± 3%   -2.07%  (p=0.043 n=10+10)
Unicode                         142ms ± 4%        144ms ± 3%     ~     (p=0.393 n=10+10)
GoTypes                         1.05s ± 2%        1.07s ± 2%   +1.59%  (p=0.019 n=9+9)
Compiler                        4.09s ± 2%        4.11s ± 1%     ~     (p=0.218 n=10+10)
SSA                             12.5s ± 1%        12.7s ± 1%   +1.00%  (p=0.035 n=10+10)
Flate                           199ms ± 7%        203ms ± 5%     ~     (p=0.481 n=10+10)
GoParser                        245ms ± 3%        246ms ± 5%     ~     (p=0.780 n=9+10)
Reflect                         672ms ± 4%        688ms ± 3%   +2.42%  (p=0.015 n=10+10)
Tar                             280ms ± 4%        284ms ± 4%     ~     (p=0.123 n=10+10)
XML                             379ms ± 4%        381ms ± 2%     ~     (p=0.529 n=10+10)
LinkCompiler                    1.16s ± 4%        1.12s ± 2%   -3.03%  (p=0.001 n=10+9)
ExternalLinkCompiler            2.28s ± 3%        2.23s ± 3%   -2.51%  (p=0.011 n=8+9)
LinkWithoutDebugCompiler        686ms ± 9%        667ms ± 2%     ~     (p=0.277 n=9+8)
StdCmd                          14.1s ± 1%        14.0s ± 1%     ~     (p=0.739 n=10+10)

name                      old user-time/op  new user-time/op  delta
Template                        604ms ±23%        564ms ± 7%     ~     (p=0.661 n=10+9)
Unicode                         429ms ±40%        418ms ±37%     ~     (p=0.579 n=10+10)
GoTypes                         2.43s ±12%        2.51s ± 7%     ~     (p=0.393 n=10+10)
Compiler                        9.22s ± 3%        9.27s ± 3%     ~     (p=0.720 n=9+10)
SSA                             26.3s ± 3%        26.6s ± 2%     ~     (p=0.579 n=10+10)
Flate                           328ms ±19%        333ms ±12%     ~     (p=0.842 n=10+9)
GoParser                        387ms ± 5%        378ms ± 9%     ~     (p=0.356 n=9+10)
Reflect                         1.36s ±20%        1.43s ±21%     ~     (p=0.631 n=10+10)
Tar                             469ms ±12%        471ms ±21%     ~     (p=0.497 n=9+10)
XML                             685ms ±18%        698ms ±19%     ~     (p=0.739 n=10+10)
LinkCompiler                    1.86s ±10%        1.87s ±11%     ~     (p=0.968 n=10+9)
ExternalLinkCompiler            3.20s ±13%        3.01s ± 8%   -5.70%  (p=0.046 n=8+9)
LinkWithoutDebugCompiler        1.08s ±15%        1.09s ±20%     ~     (p=0.579 n=10+10)

name                      old alloc/op      new alloc/op      delta
Template                       36.3MB ± 0%       36.4MB ± 0%   +0.26%  (p=0.000 n=10+10)
Unicode                        28.5MB ± 0%       28.5MB ± 0%     ~     (p=0.165 n=10+10)
GoTypes                         120MB ± 0%        121MB ± 0%   +0.29%  (p=0.000 n=9+10)
Compiler                        546MB ± 0%        548MB ± 0%   +0.32%  (p=0.000 n=10+10)
SSA                            1.84GB ± 0%       1.85GB ± 0%   +0.49%  (p=0.000 n=10+10)
Flate                          22.9MB ± 0%       23.0MB ± 0%   +0.25%  (p=0.000 n=10+10)
GoParser                       27.8MB ± 0%       27.9MB ± 0%   +0.25%  (p=0.000 n=10+8)
Reflect                        77.5MB ± 0%       77.7MB ± 0%   +0.27%  (p=0.000 n=9+9)
Tar                            34.5MB ± 0%       34.6MB ± 0%   +0.23%  (p=0.000 n=10+10)
XML                            44.2MB ± 0%       44.4MB ± 0%   +0.32%  (p=0.000 n=10+10)
LinkCompiler                    239MB ± 0%        230MB ± 0%   -3.86%  (p=0.000 n=10+10)
ExternalLinkCompiler            243MB ± 0%        243MB ± 0%   +0.22%  (p=0.000 n=10+10)
LinkWithoutDebugCompiler        164MB ± 0%        155MB ± 0%   -5.45%  (p=0.000 n=10+10)

name                      old allocs/op     new allocs/op     delta
Template                         371k ± 0%         372k ± 0%   +0.44%  (p=0.000 n=10+10)
Unicode                          340k ± 0%         340k ± 0%   +0.05%  (p=0.000 n=10+10)
GoTypes                         1.32M ± 0%        1.32M ± 0%   +0.46%  (p=0.000 n=10+10)
Compiler                        5.34M ± 0%        5.37M ± 0%   +0.59%  (p=0.000 n=10+10)
SSA                             17.6M ± 0%        17.7M ± 0%   +0.63%  (p=0.000 n=10+10)
Flate                            233k ± 0%         234k ± 0%   +0.48%  (p=0.000 n=10+10)
GoParser                         309k ± 0%         310k ± 0%   +0.40%  (p=0.000 n=10+10)
Reflect                          964k ± 0%         969k ± 0%   +0.54%  (p=0.000 n=10+10)
Tar                              346k ± 0%         348k ± 0%   +0.48%  (p=0.000 n=10+9)
XML                              424k ± 0%         426k ± 0%   +0.51%  (p=0.000 n=10+10)
LinkCompiler                     751k ± 0%         645k ± 0%  -14.13%  (p=0.000 n=10+10)
ExternalLinkCompiler            1.79M ± 0%        1.69M ± 0%   -5.30%  (p=0.000 n=10+10)
LinkWithoutDebugCompiler         217k ± 0%         222k ± 0%   +2.02%  (p=0.000 n=10+10)

name                      old object-bytes  new object-bytes  delta
Template                        547kB ± 0%        559kB ± 0%   +2.17%  (p=0.000 n=10+10)
Unicode                         215kB ± 0%        216kB ± 0%   +0.60%  (p=0.000 n=10+10)
GoTypes                        1.99MB ± 0%       2.03MB ± 0%   +2.02%  (p=0.000 n=10+10)
Compiler                       7.86MB ± 0%       8.07MB ± 0%   +2.73%  (p=0.000 n=10+10)
SSA                            26.4MB ± 0%       27.2MB ± 0%   +3.27%  (p=0.000 n=10+10)
Flate                           337kB ± 0%        343kB ± 0%   +2.02%  (p=0.000 n=10+10)
GoParser                        432kB ± 0%        441kB ± 0%   +2.11%  (p=0.000 n=10+10)
Reflect                        1.33MB ± 0%       1.36MB ± 0%   +1.87%  (p=0.000 n=10+10)
Tar                             477kB ± 0%        487kB ± 0%   +2.24%  (p=0.000 n=10+10)
XML                             617kB ± 0%        632kB ± 0%   +2.33%  (p=0.000 n=10+10)

name                      old export-bytes  new export-bytes  delta
Template                       18.5kB ± 0%       18.5kB ± 0%     ~     (all equal)
Unicode                        7.92kB ± 0%       7.92kB ± 0%     ~     (all equal)
GoTypes                        35.0kB ± 0%       35.0kB ± 0%     ~     (all equal)
Compiler                        109kB ± 0%        109kB ± 0%   +0.09%  (p=0.000 n=10+10)
SSA                             137kB ± 0%        137kB ± 0%   +0.03%  (p=0.000 n=10+10)
Flate                          4.89kB ± 0%       4.89kB ± 0%     ~     (all equal)
GoParser                       8.49kB ± 0%       8.49kB ± 0%     ~     (all equal)
Reflect                        11.4kB ± 0%       11.4kB ± 0%     ~     (all equal)
Tar                            10.5kB ± 0%       10.5kB ± 0%     ~     (all equal)
XML                            16.7kB ± 0%       16.7kB ± 0%     ~     (all equal)

name                      old text-bytes    new text-bytes    delta
HelloSize                       760kB ± 0%        760kB ± 0%     ~     (all equal)
CmdGoSize                      10.8MB ± 0%       10.8MB ± 0%     ~     (all equal)

name                      old data-bytes    new data-bytes    delta
HelloSize                      10.7kB ± 0%       10.7kB ± 0%     ~     (all equal)
CmdGoSize                       312kB ± 0%        312kB ± 0%     ~     (all equal)

name                      old bss-bytes     new bss-bytes     delta
HelloSize                       122kB ± 0%        122kB ± 0%     ~     (all equal)
CmdGoSize                       146kB ± 0%        146kB ± 0%     ~     (all equal)

name                      old exe-bytes     new exe-bytes     delta
HelloSize                      1.11MB ± 0%       1.13MB ± 0%   +1.10%  (p=0.000 n=10+10)
CmdGoSize                      14.9MB ± 0%       15.0MB ± 0%   +0.77%  (p=0.000 n=10+10)

Change-Id: I42e6087cd6231dbdcfff5464e46d373474e455e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/192417Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>

src/cmd/internal/dwarf/dwarf.go

@@ -27,9 +27,6 @@ const LocPrefix = "go.loc."
 // RangePrefix is the prefix for all the symbols containing DWARF range lists.
 const RangePrefix = "go.range."
 
-// IsStmtPrefix is the prefix for all the symbols containing DWARF is_stmt info for the line number table.
-const IsStmtPrefix = "go.isstmt."
-
 // DebugLinesPrefix is the prefix for all the symbols containing DWARF debug_line information from the compiler.
 const DebugLinesPrefix = "go.debuglines."
 

src/cmd/internal/obj/link.go

@@ -406,7 +406,6 @@ type FuncInfo struct {
 	dwarfLocSym        *LSym
 	dwarfRangesSym     *LSym
 	dwarfAbsFnSym      *LSym
-	dwarfIsStmtSym     *LSym
 	dwarfDebugLinesSym *LSym
 
 	GCArgs       *LSym

src/cmd/internal/obj/objfile.go

@@ -551,7 +551,7 @@ func isDwarf64(ctxt *Link) bool {
 	return ctxt.Headtype == objabi.Haix
 }
 
-func (ctxt *Link) dwarfSym(s *LSym) (dwarfInfoSym, dwarfLocSym, dwarfRangesSym, dwarfAbsFnSym, dwarfIsStmtSym, dwarfDebugLines *LSym) {
+func (ctxt *Link) dwarfSym(s *LSym) (dwarfInfoSym, dwarfLocSym, dwarfRangesSym, dwarfAbsFnSym, dwarfDebugLines *LSym) {
 	if s.Type != objabi.STEXT {
 		ctxt.Diag("dwarfSym of non-TEXT %v", s)
 	}
@@ -564,10 +564,9 @@ func (ctxt *Link) dwarfSym(s *LSym) (dwarfInfoSym, dwarfLocSym, dwarfRangesSym,
 		if s.WasInlined() {
 			s.Func.dwarfAbsFnSym = ctxt.DwFixups.AbsFuncDwarfSym(s)
 		}
-		s.Func.dwarfIsStmtSym = ctxt.LookupDerived(s, dwarf.IsStmtPrefix+s.Name)
 		s.Func.dwarfDebugLinesSym = ctxt.LookupDerived(s, dwarf.DebugLinesPrefix+s.Name)
 	}
-	return s.Func.dwarfInfoSym, s.Func.dwarfLocSym, s.Func.dwarfRangesSym, s.Func.dwarfAbsFnSym, s.Func.dwarfIsStmtSym, s.Func.dwarfDebugLinesSym
+	return s.Func.dwarfInfoSym, s.Func.dwarfLocSym, s.Func.dwarfRangesSym, s.Func.dwarfAbsFnSym, s.Func.dwarfDebugLinesSym
 }
 
 func (s *LSym) Len() int64 {
@@ -591,14 +590,13 @@ func (ctxt *Link) fileSymbol(fn *LSym) *LSym {
 // TEXT symbol 's'. The various DWARF symbols must already have been
 // initialized in InitTextSym.
 func (ctxt *Link) populateDWARF(curfn interface{}, s *LSym, myimportpath string) {
-	info, loc, ranges, absfunc, _, lines := ctxt.dwarfSym(s)
+	info, loc, ranges, absfunc, lines := ctxt.dwarfSym(s)
 	if info.Size != 0 {
 		ctxt.Diag("makeFuncDebugEntry double process %v", s)
 	}
 	var scopes []dwarf.Scope
 	var inlcalls dwarf.InlCalls
 	if ctxt.DebugInfo != nil {
-		stmtData(ctxt, s)
 		scopes, inlcalls = ctxt.DebugInfo(s, curfn)
 	}
 	var err error

src/cmd/internal/obj/pcln.go

@@ -295,13 +295,6 @@ func pctopcdata(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg i
 	return int32(p.To.Offset)
 }
 
-// stmtData writes out pc-linked is_stmt data for eventual use in the DWARF line numbering table.
-func stmtData(ctxt *Link, cursym *LSym) {
-	var pctostmtData Pcdata
-	funcpctab(ctxt, &pctostmtData, cursym, "pctostmt", pctostmt, nil)
-	cursym.Func.dwarfIsStmtSym.P = pctostmtData.P
-}
-
 func linkpcln(ctxt *Link, cursym *LSym) {
 	pcln := &cursym.Func.Pcln
 

src/cmd/internal/obj/plist.go

@@ -137,7 +137,7 @@ func (ctxt *Link) InitTextSym(s *LSym, flag int) {
 	ctxt.Text = append(ctxt.Text, s)
 
 	// Set up DWARF entries for s.
-	info, loc, ranges, _, isstmt, lines := ctxt.dwarfSym(s)
+	info, loc, ranges, _, lines := ctxt.dwarfSym(s)
 	info.Type = objabi.SDWARFINFO
 	info.Set(AttrDuplicateOK, s.DuplicateOK())
 	if loc != nil {
@@ -148,9 +148,6 @@ func (ctxt *Link) InitTextSym(s *LSym, flag int) {
 	ranges.Type = objabi.SDWARFRANGE
 	ranges.Set(AttrDuplicateOK, s.DuplicateOK())
 	ctxt.Data = append(ctxt.Data, info, ranges)
-	isstmt.Type = objabi.SDWARFMISC
-	isstmt.Set(AttrDuplicateOK, s.DuplicateOK())
-	ctxt.Data = append(ctxt.Data, isstmt)
 	lines.Type = objabi.SDWARFLINES
 	lines.Set(AttrDuplicateOK, s.DuplicateOK())
 	ctxt.Data = append(ctxt.Data, lines)

src/cmd/internal/objabi/symkind.go

@@ -60,7 +60,6 @@ const (
 	SDWARFRANGE
 	SDWARFLOC
 	SDWARFLINES
-	SDWARFMISC
 	// ABI alias. An ABI alias symbol is an empty symbol with a
 	// single relocation with 0 size that references the native
 	// function implementation symbol.

src/cmd/link/internal/sym/symkind.go

@@ -111,7 +111,6 @@ const (
 	SDWARFRANGE
 	SDWARFLOC
 	SDWARFLINES
-	SDWARFMISC // Not really a section; informs/affects other DWARF section generation
 
 	// ABI aliases (these never appear in the output)
 	SABIALIAS
@@ -132,7 +131,6 @@ var AbiSymKindToSymKind = [...]SymKind{
 	SDWARFRANGE,
 	SDWARFLOC,
 	SDWARFLINES,
-	SDWARFMISC,
 	SABIALIAS,
 }
 

src/cmd/link/internal/sym/symkind_string.go

@@ -59,13 +59,12 @@ func _() {
 	_ = x[SDWARFRANGE-48]
 	_ = x[SDWARFLOC-49]
 	_ = x[SDWARFLINES-50]
-	_ = x[SDWARFMISC-51]
-	_ = x[SABIALIAS-52]
+	_ = x[SABIALIAS-51]
 }
 
-const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSMACHOPLTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSCONSTSDYNIMPORTSHOSTOBJSDWARFSECTSDWARFINFOSDWARFRANGESDWARFLOCSDWARFLINESSDWARFMISCSABIALIAS"
+const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSMACHOPLTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSCONSTSDYNIMPORTSHOSTOBJSDWARFSECTSDWARFINFOSDWARFRANGESDWARFLOCSDWARFLINESSABIALIAS"
 
-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, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 320, 325, 337, 349, 366, 383, 392, 398, 408, 416, 426, 436, 447, 456, 467, 477, 486}
+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, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 320, 325, 337, 349, 366, 383, 392, 398, 408, 416, 426, 436, 447, 456, 467, 476}
 
 func (i SymKind) String() string {
 	if i >= SymKind(len(_SymKind_index)-1) {