cmd/compile: enable late expansion in openDeferExit

Change-Id: I4ce9e914d22b519b00d7e19d93091f6ac0b60938
Reviewed-on: https://go-review.googlesource.com/c/go/+/248188
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -4251,6 +4251,7 @@ func (s *state) openDeferExit() {
 	s.lastDeferExit = deferExit
 	s.lastDeferCount = len(s.openDefers)
 	zeroval := s.constInt8(types.Types[TUINT8], 0)
+	testLateExpansion := ssa.LateCallExpansionEnabledWithin(s.f)
 	// Test for and run defers in reverse order
 	for i := len(s.openDefers) - 1; i >= 0; i-- {
 		r := s.openDefers[i]
@@ -4288,18 +4289,32 @@ func (s *state) openDeferExit() {
 		stksize := fn.Type.ArgWidth()
 		var ACArgs []ssa.Param
 		var ACResults []ssa.Param
+		var callArgs []*ssa.Value
 		if r.rcvr != nil {
 			// rcvr in case of OCALLINTER
 			v := s.load(r.rcvr.Type.Elem(), r.rcvr)
 			addr := s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart)
 			ACArgs = append(ACArgs, ssa.Param{Type: types.Types[TUINTPTR], Offset: int32(argStart)})
+			if testLateExpansion {
+				callArgs = append(callArgs, v)
+			} else {
 				s.store(types.Types[TUINTPTR], addr, v)
 			}
+		}
 		for j, argAddrVal := range r.argVals {
 			f := getParam(r.n, j)
 			pt := types.NewPtr(f.Type)
+			ACArgs = append(ACArgs, ssa.Param{Type: f.Type, Offset: int32(argStart + f.Offset)})
+			if testLateExpansion {
+				var a *ssa.Value
+				if !canSSAType(f.Type) {
+					a = s.newValue2(ssa.OpDereference, f.Type, argAddrVal, s.mem())
+				} else {
+					a = s.load(f.Type, argAddrVal)
+				}
+				callArgs = append(callArgs, a)
+			} else {
 				addr := s.constOffPtrSP(pt, argStart+f.Offset)
-			ACArgs = append(ACArgs, ssa.Param{Type: types.Types[TUINTPTR], Offset: int32(argStart + f.Offset)})
 				if !canSSAType(f.Type) {
 					s.move(f.Type, addr, argAddrVal)
 				} else {
@@ -4307,18 +4322,38 @@ func (s *state) openDeferExit() {
 					s.storeType(f.Type, addr, argVal, 0, false)
 				}
 			}
+		}
 		var call *ssa.Value
 		if r.closure != nil {
 			v := s.load(r.closure.Type.Elem(), r.closure)
 			s.maybeNilCheckClosure(v, callDefer)
 			codeptr := s.rawLoad(types.Types[TUINTPTR], v)
-			call = s.newValue3A(ssa.OpClosureCall, types.TypeMem, ssa.ClosureAuxCall(ACArgs, ACResults), codeptr, v, s.mem())
+			aux := ssa.ClosureAuxCall(ACArgs, ACResults)
+			if testLateExpansion {
+				callArgs = append(callArgs, s.mem())
+				call = s.newValue2A(ssa.OpClosureLECall, aux.LateExpansionResultType(), aux, codeptr, v)
+				call.AddArgs(callArgs...)
+			} else {
+				call = s.newValue3A(ssa.OpClosureCall, types.TypeMem, aux, codeptr, v, s.mem())
+			}
+		} else {
+			aux := ssa.StaticAuxCall(fn.Sym.Linksym(), ACArgs, ACResults)
+			if testLateExpansion {
+				callArgs = append(callArgs, s.mem())
+				call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
+				call.AddArgs(callArgs...)
 			} else {
 				// Do a static call if the original call was a static function or method
-			call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, ssa.StaticAuxCall(fn.Sym.Linksym(), ACArgs, ACResults), s.mem())
+				call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, aux, s.mem())
+			}
 		}
 		call.AuxInt = stksize
+		if testLateExpansion {
+			s.vars[&memVar] = s.newValue1I(ssa.OpSelectN, types.TypeMem, int64(len(ACResults)), call)
+		} else {
 			s.vars[&memVar] = call
+		}
+
 		// Make sure that the stack slots with pointers are kept live
 		// through the call (which is a pre-emption point). Also, we will
 		// use the first call of the last defer exit to compute liveness