cmd/internal/gc: change proginfo to return ProgInfo instead of writing to param

This avoids the argument appearing to escape
(due to the fact that proginfo is always called
via a function pointer).

Change-Id: Ib9351ba18c80fd89e6a1d4f19dea386d4c657337
Reviewed-on: https://go-review.googlesource.com/6518Reviewed-by: Rob Pike <r@golang.org>

src/cmd/5g/peep.go

@@ -266,7 +266,7 @@ func subprop(r0 *gc.Flow) bool {
 		if p.As == obj.AVARDEF || p.As == obj.AVARKILL {
 			continue
 		}
-		proginfo(&info, p)
+		info = proginfo(p)
 		if info.Flags&gc.Call != 0 {
 			return false
 		}

src/cmd/5g/prog.go

@@ -133,8 +133,8 @@ var progtable = [arm.ALAST]gc.ProgInfo{
 	obj.ARET: gc.ProgInfo{gc.Break, 0, 0, 0},
 }
 
-func proginfo(info *gc.ProgInfo, p *obj.Prog) {
-	*info = progtable[p.As]
+func proginfo(p *obj.Prog) (info gc.ProgInfo) {
+	info = progtable[p.As]
 	if info.Flags == 0 {
 		gc.Fatal("unknown instruction %v", p)
 	}
@@ -160,4 +160,6 @@ func proginfo(info *gc.ProgInfo, p *obj.Prog) {
 		arm.AMODU:
 		info.Regset |= RtoB(arm.REG_R12)
 	}
+
+	return
 }

src/cmd/6g/peep.go

@@ -48,7 +48,7 @@ func needc(p *obj.Prog) bool {
 	var info gc.ProgInfo
 
 	for p != nil {
-		proginfo(&info, p)
+		info = proginfo(p)
 		if info.Flags&gc.UseCarry != 0 {
 			return true
 		}
@@ -514,7 +514,7 @@ func prevl(r0 *gc.Flow, reg int) bool {
 	for r := (*gc.Flow)(gc.Uniqp(r0)); r != nil; r = gc.Uniqp(r) {
 		p = r.Prog
 		if p.To.Type == obj.TYPE_REG && int(p.To.Reg) == reg {
-			proginfo(&info, p)
+			info = proginfo(p)
 			if info.Flags&gc.RightWrite != 0 {
 				if info.Flags&gc.SizeL != 0 {
 					return true
@@ -578,7 +578,7 @@ func subprop(r0 *gc.Flow) bool {
 		if p.As == obj.AVARDEF || p.As == obj.AVARKILL {
 			continue
 		}
-		proginfo(&info, p)
+		info = proginfo(p)
 		if info.Flags&gc.Call != 0 {
 			if gc.Debug['P'] != 0 && gc.Debug['v'] != 0 {
 				fmt.Printf("\tfound %v; return 0\n", p)
@@ -826,7 +826,7 @@ func copyu(p *obj.Prog, v *obj.Addr, s *obj.Addr) int {
 		return 0
 	}
 	var info gc.ProgInfo
-	proginfo(&info, p)
+	info = proginfo(p)
 
 	if (info.Reguse|info.Regset)&RtoB(int(v.Reg)) != 0 {
 		return 2

src/cmd/6g/prog.go

@@ -237,8 +237,8 @@ var progtable = [x86.ALAST]gc.ProgInfo{
 	x86.AXORW:     gc.ProgInfo{gc.SizeW | gc.LeftRead | RightRdwr | gc.SetCarry, 0, 0, 0},
 }
 
-func proginfo(info *gc.ProgInfo, p *obj.Prog) {
-	*info = progtable[p.As]
+func proginfo(p *obj.Prog) (info gc.ProgInfo) {
+	info = progtable[p.As]
 	if info.Flags == 0 {
 		gc.Fatal("unknown instruction %v", p)
 	}
@@ -269,4 +269,6 @@ func proginfo(info *gc.ProgInfo, p *obj.Prog) {
 	if p.To.Index != x86.REG_NONE {
 		info.Regindex |= RtoB(int(p.To.Index))
 	}
+
+	return
 }

src/cmd/8g/peep.go

@@ -49,7 +49,7 @@ func needc(p *obj.Prog) bool {
 	var info gc.ProgInfo
 
 	for p != nil {
-		proginfo(&info, p)
+		info = proginfo(p)
 		if info.Flags&gc.UseCarry != 0 {
 			return true
 		}
@@ -382,7 +382,7 @@ func subprop(r0 *gc.Flow) bool {
 		if p.As == obj.AVARDEF || p.As == obj.AVARKILL {
 			continue
 		}
-		proginfo(&info, p)
+		info = proginfo(p)
 		if info.Flags&gc.Call != 0 {
 			return false
 		}
@@ -611,7 +611,7 @@ func copyu(p *obj.Prog, v *obj.Addr, s *obj.Addr) int {
 		return 0
 	}
 	var info gc.ProgInfo
-	proginfo(&info, p)
+	info = proginfo(p)
 
 	if (info.Reguse|info.Regset)&RtoB(int(v.Reg)) != 0 {
 		return 2

src/cmd/8g/prog.go

@@ -256,8 +256,8 @@ var progtable = [i386.ALAST]gc.ProgInfo{
 	i386.AXORW:    gc.ProgInfo{gc.SizeW | gc.LeftRead | RightRdwr | gc.SetCarry, 0, 0, 0},
 }
 
-func proginfo(info *gc.ProgInfo, p *obj.Prog) {
-	*info = progtable[p.As]
+func proginfo(p *obj.Prog) (info gc.ProgInfo) {
+	info = progtable[p.As]
 	if info.Flags == 0 {
 		gc.Fatal("unknown instruction %v", p)
 	}
@@ -288,4 +288,6 @@ func proginfo(info *gc.ProgInfo, p *obj.Prog) {
 	if p.To.Index != i386.REG_NONE {
 		info.Regindex |= RtoB(int(p.To.Index))
 	}
+
+	return info
 }

src/cmd/9g/peep.go

@@ -416,7 +416,7 @@ func subprop(r0 *gc.Flow) bool {
 		if p.As == obj.AVARDEF || p.As == obj.AVARKILL {
 			continue
 		}
-		proginfo(&info, p)
+		info = proginfo(p)
 		if info.Flags&gc.Call != 0 {
 			return false
 		}

src/cmd/9g/prog.go

@@ -133,12 +133,12 @@ func initproginfo() {
 	}
 }
 
-func proginfo(info *gc.ProgInfo, p *obj.Prog) {
+func proginfo(p *obj.Prog) (info gc.ProgInfo) {
 	initproginfo()
 
-	*info = progtable[p.As]
+	info = progtable[p.As]
 	if info.Flags == 0 {
-		*info = progtable[ppc64.AADD]
+		info = progtable[ppc64.AADD]
 		gc.Fatal("proginfo: unknown instruction %v", p)
 	}
 
@@ -177,6 +177,8 @@ func proginfo(info *gc.ProgInfo, p *obj.Prog) {
 
 		info.Regset |= RtoB(ppc64.REG_R3) | RtoB(ppc64.REG_R4)
 	}
+
+	return
 }
 
 // Instruction variants table.  Initially this contains entries only

src/cmd/internal/gc/go.go

@@ -1138,7 +1138,7 @@ type Arch struct {
 	Igen           func(*Node, *Node, *Node)
 	Linkarchinit   func()
 	Peep           func(*obj.Prog)
-	Proginfo       func(*ProgInfo, *obj.Prog)
+	Proginfo       func(*obj.Prog) ProgInfo
 	Regalloc       func(*Node, *Type, *Node)
 	Regfree        func(*Node)
 	Regtyp         func(*obj.Addr) bool

src/cmd/internal/gc/lex.go

@@ -1931,7 +1931,10 @@ func getr() int32 {
 			r, w := utf8.DecodeRune(buf[:i+1])
 			if r == utf8.RuneError && w == 1 {
 				lineno = lexlineno
-				Yyerror("illegal UTF-8 sequence % x", buf[:i+1])
+				// The string conversion here makes a copy for passing
+				// to fmt.Printf, so that buf itself does not escape and can
+				// be allocated on the stack.
+				Yyerror("illegal UTF-8 sequence % x", string(buf[:i+1]))
 			}
 			return int32(r)
 		}

src/cmd/internal/gc/plive.go

@@ -562,7 +562,7 @@ func progeffects(prog *obj.Prog, vars []*Node, uevar *Bvec, varkill *Bvec, avari
 	bvresetall(varkill)
 	bvresetall(avarinit)
 
-	Thearch.Proginfo(&info, prog)
+	info = Thearch.Proginfo(prog)
 	if prog.As == obj.ARET {
 		// Return instructions implicitly read all the arguments.  For
 		// the sake of correctness, out arguments must be read.  For the

src/cmd/internal/gc/popt.go

@@ -362,6 +362,8 @@ func fixjmp(firstp *obj.Prog) {
 // to allocate in every f->data field, for use by the client.
 // If size == 0, f->data will be nil.
 
+var flowmark int
+
 func Flowstart(firstp *obj.Prog, newData func() interface{}) *Graph {
 	var info ProgInfo
 
@@ -370,11 +372,11 @@ func Flowstart(firstp *obj.Prog, newData func() interface{}) *Graph {
 
 	for p := firstp; p != nil; p = p.Link {
 		p.Opt = nil // should be already, but just in case
-		Thearch.Proginfo(&info, p)
+		info = Thearch.Proginfo(p)
 		if info.Flags&Skip != 0 {
 			continue
 		}
-		p.Opt = interface{}(1)
+		p.Opt = &flowmark
 		nf++
 	}
 
@@ -417,7 +419,7 @@ func Flowstart(firstp *obj.Prog, newData func() interface{}) *Graph {
 	var p *obj.Prog
 	for f := start; f != nil; f = f.Link {
 		p = f.Prog
-		Thearch.Proginfo(&info, p)
+		info = Thearch.Proginfo(p)
 		if info.Flags&Break == 0 {
 			f1 = f.Link
 			f.S1 = f1
@@ -726,7 +728,7 @@ func mergetemp(firstp *obj.Prog) {
 	var info ProgInfo
 	for f := g.Start; f != nil; f = f.Link {
 		p = f.Prog
-		Thearch.Proginfo(&info, p)
+		info = Thearch.Proginfo(p)
 
 		if p.From.Node != nil && ((p.From.Node).(*Node)).Opt != nil && p.To.Node != nil && ((p.To.Node).(*Node)).Opt != nil {
 			Fatal("double node %v", p)
@@ -774,7 +776,7 @@ func mergetemp(firstp *obj.Prog) {
 		f = v.use
 		if f != nil && f.Data.(*Flow) == nil {
 			p = f.Prog
-			Thearch.Proginfo(&info, p)
+			info = Thearch.Proginfo(p)
 			if p.To.Node == v.node && (info.Flags&RightWrite != 0) && info.Flags&RightRead == 0 {
 				p.As = obj.ANOP
 				p.To = obj.Addr{}
@@ -794,9 +796,9 @@ func mergetemp(firstp *obj.Prog) {
 		f = v.use
 		if f != nil && f.Link == f.Data.(*Flow) && (f.Data.(*Flow)).Data.(*Flow) == nil && Uniqp(f.Link) == f {
 			p = f.Prog
-			Thearch.Proginfo(&info, p)
+			info = Thearch.Proginfo(p)
 			p1 = f.Link.Prog
-			Thearch.Proginfo(&info1, p1)
+			info1 = Thearch.Proginfo(p1)
 			const (
 				SizeAny = SizeB | SizeW | SizeL | SizeQ | SizeF | SizeD
 			)
@@ -1122,7 +1124,7 @@ func nilwalkback(fcheck *Flow) {
 
 	for f := fcheck; f != nil; f = Uniqp(f) {
 		p = f.Prog
-		Thearch.Proginfo(&info, p)
+		info = Thearch.Proginfo(p)
 		if (info.Flags&RightWrite != 0) && Thearch.Sameaddr(&p.To, &fcheck.Prog.From) {
 			// Found initialization of value we're checking for nil.
 			// without first finding the check, so this one is unchecked.
@@ -1191,7 +1193,7 @@ func nilwalkfwd(fcheck *Flow) {
 
 	for f := Uniqs(fcheck); f != nil; f = Uniqs(f) {
 		p = f.Prog
-		Thearch.Proginfo(&info, p)
+		info = Thearch.Proginfo(p)
 
 		if (info.Flags&LeftRead != 0) && Thearch.Smallindir(&p.From, &fcheck.Prog.From) {
 			fcheck.Data = &killed

src/cmd/internal/gc/reg.go

@@ -983,7 +983,7 @@ func regopt(firstp *obj.Prog) {
 		if p.As == obj.AVARDEF || p.As == obj.AVARKILL {
 			continue
 		}
-		Thearch.Proginfo(&info, p)
+		info = Thearch.Proginfo(p)
 
 		// Avoid making variables for direct-called functions.
 		if p.As == obj.ACALL && p.To.Type == obj.TYPE_MEM && p.To.Name == obj.NAME_EXTERN {