cmd/compile: enable late expansion for closure calls

This works for "normal" calls.
Defer func() and Go func() still pending.
RT calls still pending.

Change-Id: I29cbdad8c877d12c08bbf7f3f0696611de877da9
Reviewed-on: https://go-review.googlesource.com/c/go/+/247771
Trust: David Chase <[email protected]>
Run-TryBot: David Chase <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Cherry Zhang <[email protected]>

Author: dr2chase

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

@@ -4386,6 +4386,9 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 			// Deferred nil function needs to panic when the function is invoked,
 			// not the point of defer statement.
 			s.maybeNilCheckClosure(closure, k)
+			if k == callNormal && ssa.LateCallExpansionEnabledWithin(s.f) {
+				testLateExpansion = true
+			}
 		}
 	case OCALLMETH:
 		if fn.Op != ODOTMETH {
@@ -4556,7 +4559,13 @@ func (s *state) call(n *Node, k callKind, returnResultAddr bool) *ssa.Value {
 			// critical that we not clobber any arguments already
 			// stored onto the stack.
 			codeptr = s.rawLoad(types.Types[TUINTPTR], closure)
-			call = s.newValue3A(ssa.OpClosureCall, types.TypeMem, ssa.ClosureAuxCall(ACArgs, ACResults), codeptr, closure, s.mem())
+			if testLateExpansion {
+				aux := ssa.ClosureAuxCall(ACArgs, ACResults)
+				call = s.newValue2A(ssa.OpClosureLECall, aux.LateExpansionResultType(), aux, codeptr, closure)
+				call.AddArgs(callArgs...)
+			} else {
+				call = s.newValue3A(ssa.OpClosureCall, types.TypeMem, ssa.ClosureAuxCall(ACArgs, ACResults), codeptr, closure, s.mem())
+			}
 		case codeptr != nil:
 			if testLateExpansion {
 				aux := ssa.InterfaceAuxCall(ACArgs, ACResults)