cmd/compile: minor cleanup to HashDebugPos

HashDebugPos function/method included a parameter that was always
the same, and a variable in the same package as the hashdebug code.
So remove it.

(I wrote that code, there was no reason for it to be that way).

Also corrects a stale comment in the loopvar code.

Change-Id: Id3da69cfe6dadeb31d5de62fb76d15103a5d6152
Reviewed-on: https://go-review.googlesource.com/c/go/+/482816
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

src/cmd/compile/internal/base/flag.go

@@ -208,8 +208,8 @@ func ParseFlags() {
 	//  GOCOMPILEDEBUG=loopvarhash=... -- search for failure cause
 	//
 	//  (*) For debugging purposes, providing loopvar flag >= 11 will expand the hash-eligible set of loops to all.
-	// (**) Currently this applies to all code in the compilation of some_package, including
-	//     inlines from other packages that may have been compiled w/o the change.
+	// (**) Loop semantics, changed or not, follow code from a package when it is inlined; that is, the behavior
+	//      of an application compiled with partially modified loop semantics does not depend on inlining.
 
 	if Debug.LoopVarHash != "" {
 		// This first little bit controls the inputs for debug-hash-matching.

src/cmd/compile/internal/base/hashdebug.go

@@ -138,6 +138,10 @@ func DebugHashMatch(pkgAndName string) bool {
 	return hashDebug.DebugHashMatch(pkgAndName)
 }
 
+func DebugHashMatchPos(pos src.XPos) bool {
+	return hashDebug.DebugHashMatchPos(pos)
+}
+
 // HasDebugHash returns true if Flags.Gossahash is non-empty, which
 // results in hashDebug being not-nil.  I.e., if !HasDebugHash(),
 // there is no need to create the string for hashing and testing.
@@ -317,7 +321,7 @@ func (d *HashDebug) DebugHashMatchParam(pkgAndName string, param uint64) bool {
 // locking is also more frequent and more granular.
 // Note that the default answer for no environment variable (d == nil)
 // is "yes", do the thing.
-func (d *HashDebug) DebugHashMatchPos(ctxt *obj.Link, pos src.XPos) bool {
+func (d *HashDebug) DebugHashMatchPos(pos src.XPos) bool {
 	if d == nil {
 		return true
 	}
@@ -325,7 +329,7 @@ func (d *HashDebug) DebugHashMatchPos(ctxt *obj.Link, pos src.XPos) bool {
 		return false
 	}
 	// Written this way to make inlining likely.
-	return d.debugHashMatchPos(ctxt, pos)
+	return d.debugHashMatchPos(Ctxt, pos)
 }
 
 func (d *HashDebug) debugHashMatchPos(ctxt *obj.Link, pos src.XPos) bool {

src/cmd/compile/internal/loopvar/loopvar.go

@@ -71,7 +71,7 @@ func ForCapture(fn *ir.Func) []*ir.Name {
 		// subject to hash-variable debugging.
 		maybeReplaceVar := func(k ir.Node, x *ir.RangeStmt) ir.Node {
 			if n, ok := k.(*ir.Name); ok && possiblyLeaked[n] {
-				if base.LoopVarHash.DebugHashMatchPos(base.Ctxt, n.Pos()) {
+				if base.LoopVarHash.DebugHashMatchPos(n.Pos()) {
 					// Rename the loop key, prefix body with assignment from loop key
 					transformed = append(transformed, n)
 					tk := typecheck.Temp(n.Type())
@@ -167,7 +167,7 @@ func ForCapture(fn *ir.Func) []*ir.Name {
 				forAllDefInInit(x, func(z ir.Node) {
 					if n, ok := z.(*ir.Name); ok && possiblyLeaked[n] {
 						// Hash on n.Pos() for most precise failure location.
-						if base.LoopVarHash.DebugHashMatchPos(base.Ctxt, n.Pos()) {
+						if base.LoopVarHash.DebugHashMatchPos(n.Pos()) {
 							leaked = append(leaked, n)
 						}
 					}

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

@@ -808,6 +808,5 @@ func (f *Func) useFMA(v *Value) bool {
 	if base.FmaHash == nil {
 		return true
 	}
-	ctxt := v.Block.Func.Config.Ctxt()
-	return base.FmaHash.DebugHashMatchPos(ctxt, v.Pos)
+	return base.FmaHash.DebugHashMatchPos(v.Pos)
 }