cmd/compile: return (and receive) medium-large results

includes three tests

Change-Id: I33ac0cfe35085d4b6ad2775abcaa3d7d6527b49f
Reviewed-on: https://go-review.googlesource.com/c/go/+/297031
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -248,7 +248,7 @@ func (x *expandState) splitSlots(ls []LocalSlot, sfx string, offset int64, ty *t
 }
 
 // prAssignForArg returns the ABIParamAssignment for v, assumed to be an OpArg.
-func (x *expandState) prAssignForArg(v *Value) abi.ABIParamAssignment {
+func (x *expandState) prAssignForArg(v *Value) *abi.ABIParamAssignment {
 	if v.Op != OpArg {
 		panic(badVal("Wanted OpArg, instead saw", v))
 	}
@@ -256,13 +256,12 @@ func (x *expandState) prAssignForArg(v *Value) abi.ABIParamAssignment {
 }
 
 // ParamAssignmentForArgName returns the ABIParamAssignment for f's arg with matching name.
-func ParamAssignmentForArgName(f *Func, name *ir.Name) abi.ABIParamAssignment {
+func ParamAssignmentForArgName(f *Func, name *ir.Name) *abi.ABIParamAssignment {
 	abiInfo := f.OwnAux.abiInfo
-	// This is unfortunate, but apparently the only way.
+	ip := abiInfo.InParams()
-	// TODO after register args stabilize, find a better way
+	for i, a := range ip {
-	for _, a := range abiInfo.InParams() {
 		if a.Name == name {
-			return a
+			return &ip[i]
 		}
 	}
 	panic(fmt.Errorf("Did not match param %v in prInfo %+v", name, abiInfo.InParams()))
@@ -646,6 +645,7 @@ func (x *expandState) storeArgOrLoad(pos src.XPos, b *Block, source, mem *Value,
 		fmt.Printf("\tstoreArgOrLoad(%s;  %s;  %s; %d; %s)\n", source.LongString(), mem.String(), t.String(), offset, storeRc.String())
 	}
 
+	// Start with Opcodes that can be disassembled
 	switch source.Op {
 	case OpCopy:
 		return x.storeArgOrLoad(pos, b, source.Args[0], mem, t, offset, loadRegOffset, storeRc)
@@ -1025,17 +1025,12 @@ func expandCalls(f *Func) {
 						t = tSrc
 					}
 				}
-				if iAEATt {
-					if x.debug {
-						fmt.Printf("Splitting store %s\n", v.LongString())
-					}
 				dst, mem := v.Args[0], v.Args[2]
 				mem = x.storeArgOrLoad(v.Pos, b, source, mem, t, 0, 0, registerCursor{storeDest: dst})
 				v.copyOf(mem)
 			}
 		}
 	}
-	}
 
 	val2Preds := make(map[*Value]int32) // Used to accumulate dependency graph of selection operations for topological ordering.
 
@@ -1322,14 +1317,12 @@ func (x *expandState) newArgToMemOrRegs(baseArg, toReplace *Value, offset int64,
 	}
 
 	pa := x.prAssignForArg(baseArg)
-	switch len(pa.Registers) {
+	if len(pa.Registers) == 0 { // Arg is on stack
-	case 0:
 		frameOff := baseArg.Aux.(*ir.Name).FrameOffset()
 		if pa.Offset() != int32(frameOff+x.f.ABISelf.LocalsOffset()) {
 			panic(fmt.Errorf("Parameter assignment %d and OpArg.Aux frameOffset %d disagree, op=%s",
 				pa.Offset(), frameOff, baseArg.LongString()))
 		}
-
 		aux := baseArg.Aux
 		auxInt := baseArg.AuxInt + offset
 		if toReplace != nil && toReplace.Block == baseArg.Block {
@@ -1350,8 +1343,8 @@ func (x *expandState) newArgToMemOrRegs(baseArg, toReplace *Value, offset int64,
 			}
 			return w
 		}
-
+	}
-	default:
+	// Arg is in registers
 	r := pa.Registers[regOffset]
 	auxInt := x.f.ABISelf.FloatIndexFor(r)
 	op := OpArgFloatReg
@@ -1380,7 +1373,6 @@ func (x *expandState) newArgToMemOrRegs(baseArg, toReplace *Value, offset int64,
 		return w
 	}
 }
-}
 
 // argOpAndRegisterFor converts an abi register index into an ssa Op and corresponding
 // arg register index.

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

@@ -133,7 +133,9 @@ func (a *AuxCall) Reg(i *regInfo, c *Config) *regInfo {
 	a.reg.clobbers = i.clobbers
 	return a.reg
 }
-
+func (a *AuxCall) ABI() *abi.ABIConfig {
+	return a.abiInfo.Config()
+}
 func (a *AuxCall) ResultReg(c *Config) *regInfo {
 	if a.abiInfo.OutRegistersUsed() == 0 {
 		return a.reg
@@ -162,6 +164,11 @@ func archRegForAbiReg(r abi.RegIndex, c *Config) uint8 {
 	return uint8(m)
 }
 
+// OffsetOfResult returns the SP offset of result which (indexed 0, 1, etc).
+func (a *AuxCall) ParamAssignmentForResult(which int64) *abi.ABIParamAssignment {
+	return a.abiInfo.OutParam(int(which))
+}
+
 // OffsetOfResult returns the SP offset of result which (indexed 0, 1, etc).
 func (a *AuxCall) OffsetOfResult(which int64) int64 {
 	n := int64(a.abiInfo.OutParam(int(which)).Offset())

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

@@ -563,16 +563,9 @@ func buildssa(fn *ir.Func, worker int) *ssa.Func {
 					} else { // Too big for SSA.
 						// Brute force, and early, do a bunch of stores from registers
 						// TODO fix the nasty storeArgOrLoad recursion in ssa/expand_calls.go so this Just Works with store of a big Arg.
-						typs, offs := paramAssignment.RegisterTypesAndOffsets()
+						abi := s.f.ABISelf
-						for i, t := range typs {
+						addr := s.decladdrs[n]
-							o := offs[i]
+						s.storeParameterRegsToStack(abi, paramAssignment, n, addr)
-							r := paramAssignment.Registers[i]
-							op, reg := ssa.ArgOpAndRegisterFor(r, s.f.ABISelf)
-							v := s.newValue0I(op, t, reg)
-							v.Aux = &ssa.AuxNameOffset{Name: n, Offset: o}
-							p := s.newValue1I(ssa.OpOffPtr, types.NewPtr(n.Type()), o, s.decladdrs[n])
-							s.store(t, p, v)
-						}
 					}
 				}
 			}
@@ -648,6 +641,20 @@ func buildssa(fn *ir.Func, worker int) *ssa.Func {
 	return s.f
 }
 
+func (s *state) storeParameterRegsToStack(abi *abi.ABIConfig, paramAssignment *abi.ABIParamAssignment, n *ir.Name, addr *ssa.Value) {
+	typs, offs := paramAssignment.RegisterTypesAndOffsets()
+	for i, t := range typs {
+		r := paramAssignment.Registers[i]
+		o := offs[i]
+		op, reg := ssa.ArgOpAndRegisterFor(r, abi)
+		aux := &ssa.AuxNameOffset{Name: n, Offset: o}
+		v := s.newValue0I(op, t, reg)
+		v.Aux = aux
+		p := s.newValue1I(ssa.OpOffPtr, types.NewPtr(t), o, addr)
+		s.store(t, p, v)
+	}
+}
+
 // zeroResults zeros the return values at the start of the function.
 // We need to do this very early in the function.  Defer might stop a
 // panic and show the return values as they exist at the time of
@@ -2968,12 +2975,7 @@ func (s *state) expr(n ir.Node) *ssa.Value {
 		if which == -1 {
 			panic(fmt.Errorf("ORESULT %v does not match call %s", n, s.prevCall))
 		}
-		if TypeOK(n.Type()) {
+		return s.resultOfCall(s.prevCall, which, n.Type())
-			return s.newValue1I(ssa.OpSelectN, n.Type(), which, s.prevCall)
-		} else {
-			addr := s.newValue1I(ssa.OpSelectNAddr, types.NewPtr(n.Type()), which, s.prevCall)
-			return s.rawLoad(n.Type(), addr)
-		}
 
 	case ir.ODEREF:
 		n := n.(*ir.StarExpr)
@@ -3174,6 +3176,30 @@ func (s *state) expr(n ir.Node) *ssa.Value {
 	}
 }
 
+func (s *state) resultOfCall(c *ssa.Value, which int64, t *types.Type) *ssa.Value {
+	aux := c.Aux.(*ssa.AuxCall)
+	pa := aux.ParamAssignmentForResult(which)
+	// TODO(register args) determine if in-memory TypeOK is better loaded early from SelectNAddr or later when SelectN is expanded.
+	// SelectN is better for pattern-matching and possible call-aware analysis we might want to do in the future.
+	if len(pa.Registers) == 0 && !TypeOK(t) {
+		addr := s.newValue1I(ssa.OpSelectNAddr, types.NewPtr(t), which, c)
+		return s.rawLoad(t, addr)
+	}
+	return s.newValue1I(ssa.OpSelectN, t, which, c)
+}
+
+func (s *state) resultAddrOfCall(c *ssa.Value, which int64, t *types.Type) *ssa.Value {
+	aux := c.Aux.(*ssa.AuxCall)
+	pa := aux.ParamAssignmentForResult(which)
+	if len(pa.Registers) == 0 {
+		return s.newValue1I(ssa.OpSelectNAddr, types.NewPtr(t), which, c)
+	}
+	_, addr := s.temp(c.Pos, t)
+	rval := s.newValue1I(ssa.OpSelectN, t, which, c)
+	s.vars[memVar] = s.newValue3Apos(ssa.OpStore, types.TypeMem, t, addr, rval, s.mem(), false)
+	return addr
+}
+
 // append converts an OAPPEND node to SSA.
 // If inplace is false, it converts the OAPPEND expression n to an ssa.Value,
 // adds it to s, and returns the Value.
@@ -5068,10 +5094,8 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 	}
 	fp := res.Field(0)
 	if returnResultAddr {
-		pt := types.NewPtr(fp.Type)
+		return s.resultAddrOfCall(call, 0, fp.Type)
-		return s.newValue1I(ssa.OpSelectNAddr, pt, 0, call)
 	}
-
 	return s.newValue1I(ssa.OpSelectN, fp.Type, 0, call)
 }
 
@@ -5169,9 +5193,7 @@ func (s *state) addr(n ir.Node) *ssa.Value {
 	case ir.ORESULT:
 		// load return from callee
 		n := n.(*ir.ResultExpr)
-		x := s.newValue1I(ssa.OpSelectNAddr, t, n.Index, s.prevCall)
+		return s.resultAddrOfCall(s.prevCall, n.Index, n.Type())
-		return x
-
 	case ir.OINDEX:
 		n := n.(*ir.IndexExpr)
 		if n.X.Type().IsSlice() {
@@ -5528,12 +5550,7 @@ func (s *state) rtcall(fn *obj.LSym, returns bool, results []*types.Type, args .
 	res := make([]*ssa.Value, len(results))
 	for i, t := range results {
 		off = types.Rnd(off, t.Alignment())
-		if TypeOK(t) {
+		res[i] = s.resultOfCall(call, int64(i), t)
-			res[i] = s.newValue1I(ssa.OpSelectN, t, int64(i), call)
-		} else {
-			addr := s.newValue1I(ssa.OpSelectNAddr, types.NewPtr(t), int64(i), call)
-			res[i] = s.rawLoad(t, addr)
-		}
 		off += t.Size()
 	}
 	off = types.Rnd(off, int64(types.PtrSize))
@@ -6233,9 +6250,7 @@ func (s *state) dottype(n *ir.TypeAssertExpr, commaok bool) (res, resok *ssa.Val
 	if commaok && !TypeOK(n.Type()) {
 		// unSSAable type, use temporary.
 		// TODO: get rid of some of these temporaries.
-		tmp = typecheck.TempAt(n.Pos(), s.curfn, n.Type())
+		tmp, addr = s.temp(n.Pos(), n.Type())
-		s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, tmp.(*ir.Name), s.mem())
-		addr = s.addr(tmp)
 	}
 
 	cond := s.newValue2(ssa.OpEqPtr, types.Types[types.TBOOL], itab, targetITab)
@@ -6317,6 +6332,14 @@ func (s *state) dottype(n *ir.TypeAssertExpr, commaok bool) (res, resok *ssa.Val
 	return res, resok
 }
 
+// temp allocates a temp of type t at position pos
+func (s *state) temp(pos src.XPos, t *types.Type) (*ir.Name, *ssa.Value) {
+	tmp := typecheck.TempAt(pos, s.curfn, t)
+	s.vars[memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, tmp, s.mem())
+	addr := s.addr(tmp)
+	return tmp, addr
+}
+
 // variable returns the value of a variable at the current location.
 func (s *state) variable(n ir.Node, t *types.Type) *ssa.Value {
 	v := s.vars[n]

test/abi/double_nested_addressed_struct.go

@@ -0,0 +1,62 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// wasm is excluded because the compiler chatter about register abi pragma ends up
+// on stdout, and causes the expected output to not match.
+
+package main
+
+import (
+	"fmt"
+)
+
+var sink *string
+
+type stringPair struct {
+	a, b string
+}
+
+type stringPairPair struct {
+	x, y stringPair
+}
+
+// The goal of this test is to be sure that the call arg/result expander works correctly
+// for a corner case of passing a 2-nested struct that fits in registers to/from calls.
+// AND, the struct has its address taken.
+
+//go:registerparams
+//go:noinline
+func H(spp stringPairPair) string {
+	F(&spp)
+	return spp.x.a + " " + spp.x.b + " " + spp.y.a + " " + spp.y.b
+}
+
+//go:registerparams
+//go:noinline
+func G(d, c, b, a string) stringPairPair {
+	return stringPairPair{stringPair{a, b}, stringPair{c, d}}
+}
+
+//go:registerparams
+//go:noinline
+func F(spp *stringPairPair) {
+	spp.x.a, spp.x.b, spp.y.a, spp.y.b = spp.y.b, spp.y.a, spp.x.b, spp.x.a
+}
+
+func main() {
+	spp := G("this", "is", "a", "test")
+	s := H(spp)
+	gotVsWant(s, "this is a test")
+}
+
+func gotVsWant(got, want string) {
+	if got != want {
+		fmt.Printf("FAIL, got %s, wanted %s\n", got, want)
+	}
+}

test/abi/double_nested_struct.go

@@ -0,0 +1,55 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// wasm is excluded because the compiler chatter about register abi pragma ends up
+// on stdout, and causes the expected output to not match. 
+
+package main
+
+import (
+	"fmt"
+)
+
+var sink *string
+
+type stringPair struct {
+	a, b string
+}
+
+type stringPairPair struct {
+	x, y stringPair
+}
+
+// The goal of this test is to be sure that the call arg/result expander works correctly
+// for a corner case of passing a 2-nested struct that fits in registers to/from calls.
+
+//go:registerparams
+//go:noinline
+func H(spp stringPairPair) string {
+	return spp.x.a + " " + spp.x.b + " " + spp.y.a + " " + spp.y.b
+}
+
+//go:registerparams
+//go:noinline
+func G(a,b,c,d string) stringPairPair {
+	return stringPairPair{stringPair{a,b},stringPair{c,d}}
+}
+
+
+func main() {
+	spp := G("this","is","a","test")
+	s := H(spp)
+	gotVsWant(s, "this is a test")
+}
+
+func gotVsWant(got, want string) {
+	if got != want {
+		fmt.Printf("FAIL, got %s, wanted %s\n", got, want)
+	}
+}

test/abi/too_big_to_ssa.go

@@ -0,0 +1,47 @@
+// run
+
+// +build !wasm
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+)
+
+var sink *string
+
+type toobig struct {
+	// 6 words will not SSA but will fit in registers
+	a,b,c string
+}
+
+//go:registerparams
+//go:noinline
+func H(x toobig) string {
+	return x.a + " " + x.b + " " + x.c
+}
+
+//go:registerparams
+//go:noinline
+func I(a,b,c string) toobig {
+	return toobig{a,b,c}
+}
+
+func main() {
+	s := H(toobig{"Hello", "there,", "World"})
+	gotVsWant(s, "Hello there, World")
+	fmt.Println(s)
+	t := H(I("Ahoy", "there,", "Matey"))
+	gotVsWant(t, "Ahoy there, Matey")
+	fmt.Println(t)
+}
+
+func gotVsWant(got, want string) {
+	if got != want {
+		fmt.Printf("FAIL, got %s, wanted %s\n", got, want)
+	}
+}

test/abi/too_big_to_ssa.out

@@ -0,0 +1,2 @@
+Hello there, World
+Ahoy there, Matey