cmd/compile: move hasdefer to Func

Passes toolstash -cmp.

Updates #15756

Change-Id: Ia071dbbd7f2ee0f8433d8c37af4f7b588016244e
Reviewed-on: https://go-review.googlesource.com/38231Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -251,8 +251,6 @@ var Stksize int64 // stack size for current frame
 
 var stkptrsize int64 // prefix of stack containing pointers
 
-var hasdefer bool // flag that curfn has defer statement
-
 var Curfn *Node
 
 var Widthptr int

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

@@ -340,7 +340,6 @@ func compile(fn *Node) {
 		return
 	}
 
-	hasdefer = false
 	walk(fn)
 	if nerrors != 0 {
 		return

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

@@ -1092,7 +1092,7 @@ func livenessepilogue(lv *Liveness) {
 	// pointers to copy values back to the stack).
 	// TODO: if the output parameter is heap-allocated, then we
 	// don't need to keep the stack copy live?
-	if hasdefer {
+	if lv.fn.Func.HasDefer() {
 		for i, n := range lv.vars {
 			if n.Class == PPARAMOUT {
 				if n.IsOutputParamHeapAddr() {

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

@@ -47,6 +47,7 @@ func buildssa(fn *Node) *ssa.Func {
 	s.pushLine(fn.Pos)
 	defer s.popLine()
 
+	s.hasdefer = fn.Func.HasDefer()
 	if fn.Func.Pragma&CgoUnsafeArgs != 0 {
 		s.cgoUnsafeArgs = true
 	}
@@ -218,6 +219,7 @@ type state struct {
 	placeholder *ssa.Value
 
 	cgoUnsafeArgs bool
+	hasdefer      bool // whether the function contains a defer statement
 }
 
 type funcLine struct {
@@ -877,7 +879,7 @@ func (s *state) stmt(n *Node) {
 // It returns a BlockRet block that ends the control flow. Its control value
 // will be set to the final memory state.
 func (s *state) exit() *ssa.Block {
-	if hasdefer {
+	if s.hasdefer {
 		s.rtcall(Deferreturn, true, nil)
 	}
 
@@ -3189,7 +3191,7 @@ func (s *state) canSSA(n *Node) bool {
 	case PEXTERN:
 		return false
 	case PPARAMOUT:
-		if hasdefer {
+		if s.hasdefer {
 			// TODO: handle this case?  Named return values must be
 			// in memory so that the deferred function can see them.
 			// Maybe do: if !strings.HasPrefix(n.String(), "~") { return false }

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

@@ -342,6 +342,7 @@ const (
 	funcReflectMethod             // function calls reflect.Type.Method or MethodByName
 	funcIsHiddenClosure
 	funcNoFramePointer // Must not use a frame pointer for this function
+	funcHasDefer       // contains a defer statement
 )
 
 func (f *Func) Dupok() bool           { return f.flags&funcDupok != 0 }
@@ -350,6 +351,7 @@ func (f *Func) Needctxt() bool        { return f.flags&funcNeedctxt != 0 }
 func (f *Func) ReflectMethod() bool   { return f.flags&funcReflectMethod != 0 }
 func (f *Func) IsHiddenClosure() bool { return f.flags&funcIsHiddenClosure != 0 }
 func (f *Func) NoFramePointer() bool  { return f.flags&funcNoFramePointer != 0 }
+func (f *Func) HasDefer() bool        { return f.flags&funcHasDefer != 0 }
 
 func (f *Func) SetDupok(b bool)           { f.flags.set(funcDupok, b) }
 func (f *Func) SetWrapper(b bool)         { f.flags.set(funcWrapper, b) }
@@ -357,6 +359,7 @@ func (f *Func) SetNeedctxt(b bool)        { f.flags.set(funcNeedctxt, b) }
 func (f *Func) SetReflectMethod(b bool)   { f.flags.set(funcReflectMethod, b) }
 func (f *Func) SetIsHiddenClosure(b bool) { f.flags.set(funcIsHiddenClosure, b) }
 func (f *Func) SetNoFramePointer(b bool)  { f.flags.set(funcNoFramePointer, b) }
+func (f *Func) SetHasDefer(b bool)        { f.flags.set(funcHasDefer, b) }
 
 type Op uint8
 

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

@@ -247,7 +247,7 @@ func walkstmt(n *Node) *Node {
 		n.Right = walkstmt(n.Right)
 
 	case ODEFER:
-		hasdefer = true
+		Curfn.Func.SetHasDefer(true)
 		switch n.Left.Op {
 		case OPRINT, OPRINTN:
 			n.Left = walkprintfunc(n.Left, &n.Ninit)