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cmd/compile: fixed which-result confusion in presence of 0-width types

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A function returning multiple results, some of them zero-width,
will have more than one result present at an offset.  Be sure
that offset AND type match.

Includes test.

Change-Id: I3eb1f56116d989b4e73f533fefabb1bf554c901b
Reviewed-on: https://go-review.googlesource.com/c/go/+/297169
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
David Chase 2021-02-26 17:37:26 -05:00
parent d9fd38e68b
commit 998fe70b68
4 changed files with 42 additions and 5 deletions
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9
src/cmd/compile/internal/ssa/op.go
View File

@ -86,12 +86,15 @@ type AuxCall struct {
abiInfo *abi.ABIParamResultInfo // TODO remove fields above redundant with this information.
}
// ResultForOffset returns the index of the result at a particular offset among the results
// ResultForOffsetAndType returns the index of a t-typed result at *A* particular offset among the results.
// An arbitrary number of zero-width-typed results may reside at the same offset with a single not-zero-width
// typed result, but the ones with the same type are all indistinguishable so it doesn't matter "which one"
// is obtained.
// This does not include the mem result for the call opcode.
func (a *AuxCall) ResultForOffset(offset int64) int64 {
func (a *AuxCall) ResultForOffsetAndType(offset int64, t *types.Type) int64 {
which := int64(-1)
for i := int64(0); i < a.NResults(); i++ { // note aux NResults does not include mem result.
if a.OffsetOfResult(i) == offset {
if a.OffsetOfResult(i) == offset && a.TypeOfResult(i) == t {
which = i
break
}

4
src/cmd/compile/internal/ssagen/ssa.go
View File

@ -2909,7 +2909,7 @@ func (s *state) expr(n ir.Node) *ssa.Value {
addr := s.constOffPtrSP(types.NewPtr(n.Type()), n.Offset)
return s.rawLoad(n.Type(), addr)
}
which := s.prevCall.Aux.(*ssa.AuxCall).ResultForOffset(n.Offset)
which := s.prevCall.Aux.(*ssa.AuxCall).ResultForOffsetAndType(n.Offset, n.Type())
if which == -1 {
// Do the old thing // TODO: Panic instead.
addr := s.constOffPtrSP(types.NewPtr(n.Type()), n.Offset)
@ -5119,7 +5119,7 @@ func (s *state) addr(n ir.Node) *ssa.Value {
if s.prevCall == nil || s.prevCall.Op != ssa.OpStaticLECall && s.prevCall.Op != ssa.OpInterLECall && s.prevCall.Op != ssa.OpClosureLECall {
return s.constOffPtrSP(t, n.Offset)
}
which := s.prevCall.Aux.(*ssa.AuxCall).ResultForOffset(n.Offset)
which := s.prevCall.Aux.(*ssa.AuxCall).ResultForOffsetAndType(n.Offset, n.Type())
if which == -1 {
// Do the old thing // TODO: Panic instead.
return s.constOffPtrSP(t, n.Offset)

33
test/abi/f_ret_z_not.go Normal file
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@ -0,0 +1,33 @@
// run
// 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"
type Z struct {
}
type NZ struct {
x, y int
}
//go:noinline
func f(x,y int) (Z,NZ,Z) {
var z Z
return z,NZ{x,y},z
}
//go:noinline
func g() (Z,NZ,Z) {
a,b,c := f(3,4)
return c,b,a
}
func main() {
_,b,_ := g()
fmt.Println(b.x+b.y)
}

1
test/abi/f_ret_z_not.out Normal file
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@ -0,0 +1 @@
7