cmd/compile: make Stksize local

Passes toolstash -cmp. No compiler performance impact.

Updates #15756

Change-Id: I85b45244453ae28d4da76be4313badddcbf3f5dc
Reviewed-on: https://go-review.googlesource.com/38330
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/dcl.go

@@ -1199,8 +1199,6 @@ func addmethod(msym *Sym, t *Type, local, nointerface bool) {
 }
 
 func funccompile(n *Node) {
-	Stksize = BADWIDTH
-
 	if n.Type == nil {
 		if nerrors == 0 {
 			Fatalf("funccompile missing type")
@@ -1215,7 +1213,6 @@ func funccompile(n *Node) {
 		Fatalf("funccompile %v inside %v", n.Func.Nname.Sym, Curfn.Func.Nname.Sym)
 	}
 
-	Stksize = 0
 	dclcontext = PAUTO
 	funcdepth = n.Func.Depth + 1
 	compile(n)

src/cmd/compile/internal/gc/go.go

@@ -245,8 +245,6 @@ var dclcontext Class // PEXTERN/PAUTO
 
 var statuniqgen int // name generator for static temps
 
-var Stksize int64 // stack size for current frame
-
 var stkptrsize int64 // prefix of stack containing pointers
 
 var Curfn *Node

src/cmd/compile/internal/gc/pgen.go

@@ -221,7 +221,7 @@ func (s byStackVar) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 var scratchFpMem *Node
 
 func (s *ssafn) AllocFrame(f *ssa.Func) {
-	Stksize = 0
+	s.stksize = 0
 	stkptrsize = 0
 	fn := s.curfn.Func
 
@@ -277,22 +277,22 @@ func (s *ssafn) AllocFrame(f *ssa.Func) {
 		if w >= thearch.MAXWIDTH || w < 0 {
 			Fatalf("bad width")
 		}
-		Stksize += w
-		Stksize = Rnd(Stksize, int64(n.Type.Align))
+		s.stksize += w
+		s.stksize = Rnd(s.stksize, int64(n.Type.Align))
 		if haspointers(n.Type) {
-			stkptrsize = Stksize
+			stkptrsize = s.stksize
 		}
 		if thearch.LinkArch.InFamily(sys.MIPS, sys.MIPS64, sys.ARM, sys.ARM64, sys.PPC64, sys.S390X) {
-			Stksize = Rnd(Stksize, int64(Widthptr))
+			s.stksize = Rnd(s.stksize, int64(Widthptr))
 		}
-		if Stksize >= 1<<31 {
+		if s.stksize >= 1<<31 {
 			yyerrorl(s.curfn.Pos, "stack frame too large (>2GB)")
 		}
 
-		n.Xoffset = -Stksize
+		n.Xoffset = -s.stksize
 	}
 
-	Stksize = Rnd(Stksize, int64(Widthreg))
+	s.stksize = Rnd(s.stksize, int64(Widthreg))
 	stkptrsize = Rnd(stkptrsize, int64(Widthreg))
 }
 

src/cmd/compile/internal/gc/ssa.go

@@ -4357,7 +4357,7 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
 	liveness(e.curfn, ptxt, gcargs, gclocals)
 
 	// Add frame prologue. Zero ambiguously live variables.
-	thearch.Defframe(ptxt, e.curfn, Stksize+s.maxarg)
+	thearch.Defframe(ptxt, e.curfn, e.stksize+s.maxarg)
 	if Debug['f'] != 0 {
 		frame(0)
 	}
@@ -4667,8 +4667,9 @@ func fieldIdx(n *Node) int {
 // ssafn holds frontend information about a function that the backend is processing.
 // It also exports a bunch of compiler services for the ssa backend.
 type ssafn struct {
-	curfn *Node
-	log   bool
+	curfn   *Node
+	stksize int64 // stack size for current frame
+	log     bool
 }
 
 func (s *ssafn) TypeBool() ssa.Type    { return Types[TBOOL] }