cmd/compile: remove -newescape flag

Drops support for old escape analysis pass. Subsequent, separate CL
will remove dead code.

While here, fix a minor error in fmt.go: it was still looking for
esc.go's NodeEscState in n.Opt() rather than escape.go's EscLocation.
But this only affected debug diagnostics printed during escape
analysis itself.

Change-Id: I62512e1b31c75ba0577550a5fd7824abc3159ed5
Reviewed-on: https://go-review.googlesource.com/c/go/+/187597Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -41,19 +41,8 @@ import (
 // not escape, then new(T) can be rewritten into a stack allocation.
 // The same is true of slice literals.
 
-// If newescape is true, then escape.go drives escape analysis instead
-// of esc.go.
-var newescape bool
-
 func escapes(all []*Node) {
-	visitBottomUp(all, escapeImpl())
-}
-
-func escapeImpl() func([]*Node, bool) {
-	if newescape {
-		return escapeFuncs
-	}
-	return escAnalyze
+	visitBottomUp(all, escapeFuncs)
 }
 
 const (

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

@@ -457,8 +457,8 @@ func (n *Node) jconv(s fmt.State, flag FmtFlag) {
 		fmt.Fprintf(s, " esc(%d)", n.Esc)
 	}
 
-	if e, ok := n.Opt().(*NodeEscState); ok && e.Loopdepth != 0 {
-		fmt.Fprintf(s, " ld(%d)", e.Loopdepth)
+	if e, ok := n.Opt().(*EscLocation); ok && e.loopDepth != 0 {
+		fmt.Fprintf(s, " ld(%d)", e.loopDepth)
 	}
 
 	if c == 0 && n.Typecheck() != 0 {

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

@@ -263,7 +263,6 @@ func Main(archInit func(*Arch)) {
 	flag.StringVar(&blockprofile, "blockprofile", "", "write block profile to `file`")
 	flag.StringVar(&mutexprofile, "mutexprofile", "", "write mutex profile to `file`")
 	flag.StringVar(&benchfile, "bench", "", "append benchmark times to `file`")
-	flag.BoolVar(&newescape, "newescape", true, "enable new escape analysis")
 	flag.BoolVar(&smallFrames, "smallframes", false, "reduce the size limit for stack allocated objects")
 	flag.BoolVar(&Ctxt.UseBASEntries, "dwarfbasentries", Ctxt.UseBASEntries, "use base address selection entries in DWARF")
 	objabi.Flagparse(usage)
@@ -271,7 +270,7 @@ func Main(archInit func(*Arch)) {
 	// Record flags that affect the build result. (And don't
 	// record flags that don't, since that would cause spurious
 	// changes in the binary.)
-	recordFlags("B", "N", "l", "msan", "race", "shared", "dynlink", "dwarflocationlists", "newescape", "dwarfbasentries", "smallframes")
+	recordFlags("B", "N", "l", "msan", "race", "shared", "dynlink", "dwarflocationlists", "dwarfbasentries", "smallframes")
 
 	if smallFrames {
 		maxStackVarSize = 128 * 1024

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

@@ -1579,7 +1579,7 @@ func genwrapper(rcvr *types.Type, method *types.Field, newnam *types.Sym) {
 	if rcvr.IsPtr() && rcvr.Elem() == method.Type.Recv().Type && rcvr.Elem().Sym != nil {
 		inlcalls(fn)
 	}
-	escapeImpl()([]*Node{fn}, false)
+	escapeFuncs([]*Node{fn}, false)
 
 	Curfn = nil
 	funccompile(fn)