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author | David Chase <drchase@google.com> | 2018-06-25 15:26:45 -0400 |
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committer | David Chase <drchase@google.com> | 2018-06-25 20:36:42 +0000 |
commit | 7e9d55eeeb183ee95d26b3ed4ff171902605decf (patch) | |
tree | 5739d3711787f80403e6616d11285454508d7b99 | |
parent | 6d709528972aa572a6dafb06cd3446348d337aa7 (diff) | |
download | go-7e9d55eeeb183ee95d26b3ed4ff171902605decf.tar.gz go-7e9d55eeeb183ee95d26b3ed4ff171902605decf.zip |
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>
-rw-r--r-- | src/cmd/compile/internal/ssa/loopbce.go | 6 | ||||
-rw-r--r-- | test/fixedbugs/issue26043.go | 32 |
2 files changed, 37 insertions, 1 deletions
diff --git a/src/cmd/compile/internal/ssa/loopbce.go b/src/cmd/compile/internal/ssa/loopbce.go index 0c09de0bfc..2ab05711ad 100644 --- a/src/cmd/compile/internal/ssa/loopbce.go +++ b/src/cmd/compile/internal/ssa/loopbce.go @@ -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 import "fmt" @@ -154,7 +158,7 @@ nextb: // if the increment is ±1 or when the limits are constants. if inc.AuxInt != 1 && inc.AuxInt != -1 { 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 ok = true } diff --git a/test/fixedbugs/issue26043.go b/test/fixedbugs/issue26043.go new file mode 100644 index 0000000000..fe32947b07 --- /dev/null +++ b/test/fixedbugs/issue26043.go @@ -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 + } +} |