[dev.typeparams] cmd/compile: remove variadic defer calls

Now that defer wrapping is used, deferred function is always
argumentless. Remove the code handling arguments.

This CL is mostly removing the fallback code path. There are more
cleanups to be done, in later CLs.

Change-Id: If6c729d3055c7a507cb1f1a000f5bbd3ad7ff235
Reviewed-on: https://go-review.googlesource.com/c/go/+/325914
Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

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

@@ -359,31 +359,8 @@ func (s *state) emitOpenDeferInfo() {
 		r := s.openDefers[i]
 		off = dvarint(x, off, r.n.X.Type().ArgWidth())
 		off = dvarint(x, off, -r.closureNode.FrameOffset())
-		numArgs := len(r.argNodes)
+		numArgs := 0
-		if r.rcvrNode != nil {
-			// If there's an interface receiver, treat/place it as the first
-			// arg. (If there is a method receiver, it's already included as
-			// first arg in r.argNodes.)
-			numArgs++
-		}
 		off = dvarint(x, off, int64(numArgs))
-		argAdjust := 0 // presence of receiver offsets the parameter count.
-		if r.rcvrNode != nil {
-			off = dvarint(x, off, -okOffset(r.rcvrNode.FrameOffset()))
-			off = dvarint(x, off, s.config.PtrSize)
-			off = dvarint(x, off, 0) // This is okay because defer records use ABI0 (for now)
-			argAdjust++
-		}
-
-		// TODO(register args) assume abi0 for this?
-		ab := s.f.ABI0
-		pri := ab.ABIAnalyzeFuncType(r.n.X.Type().FuncType())
-		for j, arg := range r.argNodes {
-			f := getParam(r.n, j)
-			off = dvarint(x, off, -okOffset(arg.FrameOffset()))
-			off = dvarint(x, off, f.Type.Size())
-			off = dvarint(x, off, okOffset(pri.InParam(j+argAdjust).FrameOffset(pri)))
-		}
 	}
 }
 
@@ -864,16 +841,6 @@ type openDeferInfo struct {
 	// function, method, or interface call, to store a closure that panic
 	// processing can use for this defer.
 	closureNode *ir.Name
-	// If defer call is interface call, the address of the argtmp where the
-	// receiver is stored
-	rcvr *ssa.Value
-	// The node representing the argtmp where the receiver is stored
-	rcvrNode *ir.Name
-	// The addresses of the argtmps where the evaluated arguments of the defer
-	// function call are stored.
-	argVals []*ssa.Value
-	// The nodes representing the argtmps where the args of the defer are stored
-	argNodes []*ir.Name
 }
 
 type state struct {
@@ -4686,17 +4653,14 @@ func (s *state) intrinsicArgs(n *ir.CallExpr) []*ssa.Value {
 	return args
 }
 
-// openDeferRecord adds code to evaluate and store the args for an open-code defer
+// openDeferRecord adds code to evaluate and store the function for an open-code defer
 // call, and records info about the defer, so we can generate proper code on the
 // exit paths. n is the sub-node of the defer node that is the actual function
-// call. We will also record funcdata information on where the args are stored
+// call. We will also record funcdata information on where the function is stored
 // (as well as the deferBits variable), and this will enable us to run the proper
 // defer calls during panics.
 func (s *state) openDeferRecord(n *ir.CallExpr) {
-	var args []*ssa.Value
+	if len(n.Args) != 0 || n.Op() != ir.OCALLFUNC || n.X.Type().NumResults() != 0 {
-	var argNodes []*ir.Name
-
-	if len(n.Args) != 0 || n.Op() == ir.OCALLINTER || n.X.Type().NumResults() != 0 {
 		s.Fatalf("defer call with arguments or results: %v", n)
 	}
 
@@ -4704,48 +4668,20 @@ func (s *state) openDeferRecord(n *ir.CallExpr) {
 		n: n,
 	}
 	fn := n.X
-	if n.Op() == ir.OCALLFUNC {
+	// We must always store the function value in a stack slot for the
-		// We must always store the function value in a stack slot for the
+	// runtime panic code to use. But in the defer exit code, we will
-		// runtime panic code to use. But in the defer exit code, we will
+	// call the function directly if it is a static function.
-		// call the function directly if it is a static function.
+	closureVal := s.expr(fn)
-		closureVal := s.expr(fn)
+	closure := s.openDeferSave(nil, fn.Type(), closureVal)
-		closure := s.openDeferSave(nil, fn.Type(), closureVal)
+	opendefer.closureNode = closure.Aux.(*ir.Name)
-		opendefer.closureNode = closure.Aux.(*ir.Name)
+	if !(fn.Op() == ir.ONAME && fn.(*ir.Name).Class == ir.PFUNC) {
-		if !(fn.Op() == ir.ONAME && fn.(*ir.Name).Class == ir.PFUNC) {
+		opendefer.closure = closure
-			opendefer.closure = closure
-		}
-	} else if n.Op() == ir.OCALLMETH {
-		base.Fatalf("OCALLMETH missed by walkCall")
-	} else {
-		if fn.Op() != ir.ODOTINTER {
-			base.Fatalf("OCALLINTER: n.Left not an ODOTINTER: %v", fn.Op())
-		}
-		fn := fn.(*ir.SelectorExpr)
-		closure, rcvr := s.getClosureAndRcvr(fn)
-		opendefer.closure = s.openDeferSave(nil, closure.Type, closure)
-		// Important to get the receiver type correct, so it is recognized
-		// as a pointer for GC purposes.
-		opendefer.rcvr = s.openDeferSave(nil, fn.Type().Recv().Type, rcvr)
-		opendefer.closureNode = opendefer.closure.Aux.(*ir.Name)
-		opendefer.rcvrNode = opendefer.rcvr.Aux.(*ir.Name)
 	}
-	for _, argn := range n.Args {
-		var v *ssa.Value
-		if TypeOK(argn.Type()) {
-			v = s.openDeferSave(nil, argn.Type(), s.expr(argn))
-		} else {
-			v = s.openDeferSave(argn, argn.Type(), nil)
-		}
-		args = append(args, v)
-		argNodes = append(argNodes, v.Aux.(*ir.Name))
-	}
-	opendefer.argVals = args
-	opendefer.argNodes = argNodes
 	index := len(s.openDefers)
 	s.openDefers = append(s.openDefers, opendefer)
 
 	// Update deferBits only after evaluation and storage to stack of
-	// args/receiver/interface is successful.
+	// the function is successful.
 	bitvalue := s.constInt8(types.Types[types.TUINT8], 1<<uint(index))
 	newDeferBits := s.newValue2(ssa.OpOr8, types.Types[types.TUINT8], s.variable(deferBitsVar, types.Types[types.TUINT8]), bitvalue)
 	s.vars[deferBitsVar] = newDeferBits
@@ -4848,45 +4784,26 @@ func (s *state) openDeferExit() {
 		s.vars[deferBitsVar] = maskedval
 
 		// Generate code to call the function call of the defer, using the
-		// closure/receiver/args that were stored in argtmps at the point
+		// closure that were stored in argtmps at the point of the defer
-		// of the defer statement.
+		// statement.
 		fn := r.n.X
 		stksize := fn.Type().ArgWidth()
-		var ACArgs []*types.Type
-		var ACResults []*types.Type
 		var callArgs []*ssa.Value
-		if r.rcvr != nil {
-			// rcvr in case of OCALLINTER
-			v := s.load(r.rcvr.Type.Elem(), r.rcvr)
-			ACArgs = append(ACArgs, types.Types[types.TUINTPTR])
-			callArgs = append(callArgs, v)
-		}
-		for j, argAddrVal := range r.argVals {
-			f := getParam(r.n, j)
-			ACArgs = append(ACArgs, f.Type)
-			var a *ssa.Value
-			if !TypeOK(f.Type) {
-				a = s.newValue2(ssa.OpDereference, f.Type, argAddrVal, s.mem())
-			} else {
-				a = s.load(f.Type, argAddrVal)
-			}
-			callArgs = append(callArgs, a)
-		}
 		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[types.TUINTPTR], v)
-			aux := ssa.ClosureAuxCall(s.f.ABIDefault.ABIAnalyzeTypes(nil, ACArgs, ACResults))
+			aux := ssa.ClosureAuxCall(s.f.ABIDefault.ABIAnalyzeTypes(nil, nil, nil))
 			call = s.newValue2A(ssa.OpClosureLECall, aux.LateExpansionResultType(), aux, codeptr, v)
 		} else {
-			aux := ssa.StaticAuxCall(fn.(*ir.Name).Linksym(), s.f.ABIDefault.ABIAnalyzeTypes(nil, ACArgs, ACResults))
+			aux := ssa.StaticAuxCall(fn.(*ir.Name).Linksym(), s.f.ABIDefault.ABIAnalyzeTypes(nil, nil, nil))
 			call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 		}
 		callArgs = append(callArgs, s.mem())
 		call.AddArgs(callArgs...)
 		call.AuxInt = stksize
-		s.vars[memVar] = s.newValue1I(ssa.OpSelectN, types.TypeMem, int64(len(ACResults)), call)
+		s.vars[memVar] = s.newValue1I(ssa.OpSelectN, types.TypeMem, 0, 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
@@ -4894,16 +4811,6 @@ func (s *state) openDeferExit() {
 		if r.closureNode != nil {
 			s.vars[memVar] = s.newValue1Apos(ssa.OpVarLive, types.TypeMem, r.closureNode, s.mem(), false)
 		}
-		if r.rcvrNode != nil {
-			if r.rcvrNode.Type().HasPointers() {
-				s.vars[memVar] = s.newValue1Apos(ssa.OpVarLive, types.TypeMem, r.rcvrNode, s.mem(), false)
-			}
-		}
-		for _, argNode := range r.argNodes {
-			if argNode.Type().HasPointers() {
-				s.vars[memVar] = s.newValue1Apos(ssa.OpVarLive, types.TypeMem, argNode, s.mem(), false)
-			}
-		}
 
 		s.endBlock()
 		s.startBlock(bEnd)
@@ -5022,17 +4929,21 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 	var call *ssa.Value
 	if k == callDeferStack {
 		// Make a defer struct d on the stack.
-		t := deferstruct(stksize)
+		if stksize != 0 {
+			s.Fatalf("deferprocStack with non-zero stack size %d: %v", stksize, n)
+		}
+
+		t := deferstruct()
 		d := typecheck.TempAt(n.Pos(), s.curfn, t)
 
 		s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, d, s.mem())
 		addr := s.addr(d)
 
-		// Must match reflect.go:deferstruct and src/runtime/runtime2.go:_defer.
+		// Must match deferstruct() below and src/runtime/runtime2.go:_defer.
 		// 0: siz
 		s.store(types.Types[types.TUINT32],
 			s.newValue1I(ssa.OpOffPtr, types.Types[types.TUINT32].PtrTo(), t.FieldOff(0), addr),
-			s.constInt32(types.Types[types.TUINT32], int32(stksize)))
+			s.constInt32(types.Types[types.TUINT32], 0))
 		// 1: started, set in deferprocStack
 		// 2: heap, set in deferprocStack
 		// 3: openDefer
@@ -5048,39 +4959,13 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 		// 10: varp
 		// 11: fd
 
-		// Then, store all the arguments of the defer call.
-		ft := fn.Type()
-		off := t.FieldOff(12) // TODO register args: be sure this isn't a hardcoded param stack offset.
-		args := n.Args
-
-		// Set receiver (for interface calls). Always a pointer.
-		if rcvr != nil {
-			p := s.newValue1I(ssa.OpOffPtr, ft.Recv().Type.PtrTo(), off, addr)
-			s.store(types.Types[types.TUINTPTR], p, rcvr)
-		}
-		// Set receiver (for method calls).
-		if n.Op() == ir.OCALLMETH {
-			base.Fatalf("OCALLMETH missed by walkCall")
-		}
-		// Set other args.
-		for _, f := range ft.Params().Fields().Slice() {
-			s.storeArgWithBase(args[0], f.Type, addr, off+abi.FieldOffsetOf(f))
-			args = args[1:]
-		}
-
 		// Call runtime.deferprocStack with pointer to _defer record.
 		ACArgs = append(ACArgs, types.Types[types.TUINTPTR])
 		aux := ssa.StaticAuxCall(ir.Syms.DeferprocStack, s.f.ABIDefault.ABIAnalyzeTypes(nil, ACArgs, ACResults))
 		callArgs = append(callArgs, addr, s.mem())
 		call = s.newValue0A(ssa.OpStaticLECall, aux.LateExpansionResultType(), aux)
 		call.AddArgs(callArgs...)
-		if stksize < int64(types.PtrSize) {
+		call.AuxInt = int64(types.PtrSize) // deferprocStack takes a *_defer arg
-			// We need room for both the call to deferprocStack and the call to
-			// the deferred function.
-			// TODO(register args) Revisit this if/when we pass args in registers.
-			stksize = int64(types.PtrSize)
-		}
-		call.AuxInt = stksize
 	} else {
 		// Store arguments to stack, including defer/go arguments and receiver for method calls.
 		// These are written in SP-offset order.
@@ -7689,9 +7574,8 @@ func max8(a, b int8) int8 {
 	return b
 }
 
-// deferstruct makes a runtime._defer structure, with additional space for
+// deferstruct makes a runtime._defer structure.
-// stksize bytes of args.
+func deferstruct() *types.Type {
-func deferstruct(stksize int64) *types.Type {
 	makefield := func(name string, typ *types.Type) *types.Field {
 		// Unlike the global makefield function, this one needs to set Pkg
 		// because these types might be compared (in SSA CSE sorting).
@@ -7699,11 +7583,8 @@ func deferstruct(stksize int64) *types.Type {
 		sym := &types.Sym{Name: name, Pkg: types.LocalPkg}
 		return types.NewField(src.NoXPos, sym, typ)
 	}
-	argtype := types.NewArray(types.Types[types.TUINT8], stksize)
-	argtype.Width = stksize
-	argtype.Align = 1
 	// These fields must match the ones in runtime/runtime2.go:_defer and
-	// cmd/compile/internal/gc/ssa.go:(*state).call.
+	// (*state).call above.
 	fields := []*types.Field{
 		makefield("siz", types.Types[types.TUINT32]),
 		makefield("started", types.Types[types.TBOOL]),
@@ -7720,7 +7601,6 @@ func deferstruct(stksize int64) *types.Type {
 		makefield("framepc", types.Types[types.TUINTPTR]),
 		makefield("varp", types.Types[types.TUINTPTR]),
 		makefield("fd", types.Types[types.TUINTPTR]),
-		makefield("args", argtype),
 	}
 
 	// build struct holding the above fields