mirror of
https://github.com/golang/go
synced 2024-10-14 20:05:36 +00:00
cmd/compile: avoid remainder in loopbce when increment=0
For non-unit increment, loopbce checks to see if the increment evenly divides the difference between (constant) loop start and end. This test panics when the increment is zero. Fix: check for zero, if found, don't optimize the loop. Also added missing copyright notice to loopbce.go. Fixes #26043. Change-Id: I5f460104879cacc94481949234c9ce8c519d6380 Reviewed-on: https://go-review.googlesource.com/120759 Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
parent
6d70952897
commit
7e9d55eeeb
|
@ -1,3 +1,7 @@
|
||||||
|
// 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 ssa
|
package ssa
|
||||||
|
|
||||||
import "fmt"
|
import "fmt"
|
||||||
|
@ -154,7 +158,7 @@ nextb:
|
||||||
// if the increment is ±1 or when the limits are constants.
|
// if the increment is ±1 or when the limits are constants.
|
||||||
if inc.AuxInt != 1 && inc.AuxInt != -1 {
|
if inc.AuxInt != 1 && inc.AuxInt != -1 {
|
||||||
ok := false
|
ok := false
|
||||||
if min.Op == OpConst64 && max.Op == OpConst64 {
|
if min.Op == OpConst64 && max.Op == OpConst64 && inc.AuxInt != 0 {
|
||||||
if max.AuxInt > min.AuxInt && max.AuxInt%inc.AuxInt == min.AuxInt%inc.AuxInt { // handle overflow
|
if max.AuxInt > min.AuxInt && max.AuxInt%inc.AuxInt == min.AuxInt%inc.AuxInt { // handle overflow
|
||||||
ok = true
|
ok = true
|
||||||
}
|
}
|
||||||
|
|
32
test/fixedbugs/issue26043.go
Normal file
32
test/fixedbugs/issue26043.go
Normal file
|
@ -0,0 +1,32 @@
|
||||||
|
// compile
|
||||||
|
|
||||||
|
// 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.
|
||||||
|
|
||||||
|
// This program results in a loop inferred to increment
|
||||||
|
// j by 0, causing bounds check elimination to attempt
|
||||||
|
// something%0, which panics (in the bug).
|
||||||
|
|
||||||
|
package q
|
||||||
|
|
||||||
|
func f() {
|
||||||
|
var s1 string
|
||||||
|
var b bool
|
||||||
|
if b {
|
||||||
|
b = !b
|
||||||
|
s1 += "a"
|
||||||
|
}
|
||||||
|
|
||||||
|
var s2 string
|
||||||
|
var i, j int
|
||||||
|
if (s1 <= "") || (s2 >= "") {
|
||||||
|
j = len(s1[:6])
|
||||||
|
} else {
|
||||||
|
i = len("b")
|
||||||
|
}
|
||||||
|
|
||||||
|
for j < 0 {
|
||||||
|
j += i
|
||||||
|
}
|
||||||
|
}
|
Loading…
Reference in a new issue