[dev.regabi] cmd/compile: fixes for big rewrite

Adjust the new regabi code a bit to make the rewrites apply cleanly.

Change-Id: Ice5378e94d94ab45ca0572f44ab8c94b847271b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/279530
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -265,20 +265,21 @@ func makeABIWrapper(f *ir.Func, wrapperABI obj.ABI) {
 	// to allocate any stack space). Doing this will require some
 	// extra work in typecheck/walk/ssa, might want to add a new node
 	// OTAILCALL or something to this effect.
-	var call ir.Node
+	var tail ir.Node
 	if tfn.Type().NumResults() == 0 && tfn.Type().NumParams() == 0 && tfn.Type().NumRecvs() == 0 {
-		call = nodSym(ir.ORETJMP, nil, f.Nname.Sym())
+		tail = nodSym(ir.ORETJMP, nil, f.Nname.Sym())
 	} else {
-		call = ir.Nod(ir.OCALL, f.Nname, nil)
+		call := ir.Nod(ir.OCALL, f.Nname, nil)
 		call.PtrList().Set(paramNnames(tfn.Type()))
 		call.SetIsDDD(tfn.Type().IsVariadic())
+		tail = call
 		if tfn.Type().NumResults() > 0 {
 			n := ir.Nod(ir.ORETURN, nil, nil)
 			n.PtrList().Set1(call)
-			call = n
+			tail = n
 		}
 	}
-	fn.PtrBody().Append(call)
+	fn.PtrBody().Append(tail)
 
 	funcbody()
 	if base.Debug.DclStack != 0 {

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

@@ -7332,18 +7332,20 @@ func callTargetLSym(callee *types.Sym, callerLSym *obj.LSym) *obj.LSym {
 	if ir.AsNode(callee.Def) == nil {
 		return lsym
 	}
-	ndclfunc := ir.AsNode(callee.Def).Name().Defn
-	if ndclfunc == nil {
+	defn := ir.AsNode(callee.Def).Name().Defn
+	if defn == nil {
 		return lsym
 	}
+	ndclfunc := defn.(*ir.Func)
+
 	// check for case 1 above
 	if callerLSym.ABIWrapper() {
-		if nlsym := ndclfunc.Func().LSym; nlsym != nil {
+		if nlsym := ndclfunc.LSym; nlsym != nil {
 			lsym = nlsym
 		}
 	} else {
 		// check for case 2 above
-		nam := ndclfunc.Func().Nname
+		nam := ndclfunc.Nname
 		defABI, hasDefABI := symabiDefs[nam.Sym().LinksymName()]
 		if hasDefABI && defABI == obj.ABI0 {
 			lsym = nam.Sym().LinksymABI0()