Commit c359d759 authored by David Chase's avatar David Chase

cmd/compile: ensure that operand of ORETURN is not double-walked

Inlining of switch statements into a RETURNed expression
can sometimes lead to the switch being walked twice, which
results in a miscompiled switch statement. The bug depends
on:

1) multiple results
2) named results
3) a return statement whose expression includes a call to a
function containing a switch statement that is inlined.

It may also be significant that the default case of that
switch is a panic(), though that's not proven.

Rearranged the walk case for ORETURN so that double walks are
not possible.  Added a test, because this is so fiddly.
Added a check against double walks, verified that it fires
w/o other fix.

Fixes #25776.

Change-Id: I2d594351fa082632512ef989af67eb887059729b
Reviewed-on: https://go-review.googlesource.com/118318
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: 's avatarCherry Zhang <cherryyz@google.com>
parent 46076c37
...@@ -241,6 +241,11 @@ func walkswitch(sw *Node) { ...@@ -241,6 +241,11 @@ func walkswitch(sw *Node) {
// search using if..goto, although binary search // search using if..goto, although binary search
// is used with long runs of constants. // is used with long runs of constants.
func (s *exprSwitch) walk(sw *Node) { func (s *exprSwitch) walk(sw *Node) {
// Guard against double walk, see #25776.
if sw.List.Len() == 0 && sw.Nbody.Len() > 0 {
Fatalf("second walk of switch")
}
casebody(sw, nil) casebody(sw, nil)
cond := sw.Left cond := sw.Left
......
...@@ -287,7 +287,6 @@ func walkstmt(n *Node) *Node { ...@@ -287,7 +287,6 @@ func walkstmt(n *Node) *Node {
walkstmtlist(n.Rlist.Slice()) walkstmtlist(n.Rlist.Slice())
case ORETURN: case ORETURN:
walkexprlist(n.List.Slice(), &n.Ninit)
if n.List.Len() == 0 { if n.List.Len() == 0 {
break break
} }
...@@ -317,6 +316,9 @@ func walkstmt(n *Node) *Node { ...@@ -317,6 +316,9 @@ func walkstmt(n *Node) *Node {
if samelist(rl, n.List.Slice()) { if samelist(rl, n.List.Slice()) {
// special return in disguise // special return in disguise
// TODO(josharian, 1.12): is "special return" still relevant?
// Tests still pass w/o this. See comments on https://go-review.googlesource.com/c/go/+/118318
walkexprlist(n.List.Slice(), &n.Ninit)
n.List.Set(nil) n.List.Set(nil)
break break
...@@ -329,6 +331,7 @@ func walkstmt(n *Node) *Node { ...@@ -329,6 +331,7 @@ func walkstmt(n *Node) *Node {
n.List.Set(reorder3(ll)) n.List.Set(reorder3(ll))
break break
} }
walkexprlist(n.List.Slice(), &n.Ninit)
ll := ascompatte(nil, false, Curfn.Type.Results(), n.List.Slice(), 1, &n.Ninit) ll := ascompatte(nil, false, Curfn.Type.Results(), n.List.Slice(), 1, &n.Ninit)
n.List.Set(ll) n.List.Set(ll)
......
// run
// Copyright 2018 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
const (
Upper = true
blas_Upper = 121
badTriangle = "bad triangle"
)
// Triangular represents a triangular matrix. Triangular matrices are always square.
type Triangular interface {
// Triangular returns the number of rows/columns in the matrix and its
// orientation.
Tryangle() (mmmm int, kynd bool)
Triangle() (mmmm int, kynd bool)
}
// blas64_Triangular represents a triangular matrix using the conventional storage scheme.
type blas64_Triangular struct {
Stride int
Uplo int
}
// TriDense represents an upper or lower triangular matrix in dense storage
// format.
type TriDense struct {
mat blas64_Triangular
}
func NewTriDense() *TriDense {
return &TriDense{
mat: blas64_Triangular{
Stride: 3,
Uplo: blas_Upper,
},
}
}
func (t *TriDense) isUpper() bool {
return isUpperUplo(t.mat.Uplo)
}
func (t *TriDense) triKind() bool {
return isUpperUplo(t.mat.Uplo)
}
func isUpperUplo(u int) bool {
switch u {
case blas_Upper:
return true
default:
panic(badTriangle)
}
}
func (t *TriDense) IsZero() bool {
return t.mat.Stride == 0
}
//go:noinline
func (t *TriDense) ScaleTri(f float64, a Triangular) {
n, kind := a.Triangle()
if kind == false {
println("ScaleTri n, kind=", n, ", ", kind, " (FAIL, expected true)")
}
}
//go:noinline
func (t *TriDense) ScaleTry(f float64, a Triangular) {
n, kind := a.Tryangle()
if kind == false {
println("ScaleTry n, kind=", n, ", ", kind, " (FAIL, expected true)")
}
}
// Triangle failed (before fix)
func (t *TriDense) Triangle() (nnnn int, kind bool) {
return 3, !t.IsZero() && t.triKind()
}
// Tryangle works -- difference is not-named output parameters.
func (t *TriDense) Tryangle() (int, bool) {
return 3, !t.IsZero() && t.triKind()
}
func main() {
ta := NewTriDense()
n, kind := ta.Triangle()
if kind == false {
println(" main n, kind=", n, ", ", kind, " (FAIL, expected true)")
}
ta.ScaleTri(1, ta)
ta.ScaleTry(1, ta)
}
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