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4c800f03c9
Pointer arithemetic is done mod 2^32 on 386, so we can just drop the high bits of any large constant offsets. The bounds check will make sure wraparounds are never observed. Fixes #21655 Change-Id: I68ae5bbea9f02c73968ea2b21ca017e5ecb89223 Reviewed-on: https://go-review.googlesource.com/82675 Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
63 lines
1.5 KiB
Go
63 lines
1.5 KiB
Go
// compile
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// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Make sure assembly offsets don't get too large.
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// To trigger issue21655, the index offset needs to be small
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// enough to fit into an int32 (to get rewritten to an ADDQconst)
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// but large enough to overflow an int32 after multiplying by the stride.
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package main
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func f1(a []int64, i int64) int64 {
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return a[i+1<<30]
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}
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func f2(a []int32, i int64) int32 {
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return a[i+1<<30]
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}
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func f3(a []int16, i int64) int16 {
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return a[i+1<<30]
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}
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func f4(a []int8, i int64) int8 {
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return a[i+1<<31]
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}
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func f5(a []float64, i int64) float64 {
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return a[i+1<<30]
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}
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func f6(a []float32, i int64) float32 {
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return a[i+1<<30]
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}
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// Note: Before the fix for issue 21655, f{1,2,5,6} made
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// the compiler crash. f3 silently generated the wrong
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// code, using an offset of -1<<31 instead of 1<<31.
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// (This is due to the assembler accepting offsets
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// like 0x80000000 and silently using them as
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// signed 32 bit offsets.)
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// f4 was ok, but testing it can't hurt.
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func f7(ss []*string, i int) string {
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const offset = 3 << 29 // 3<<29 * 4 = 3<<31 = 1<<31 mod 1<<32.
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if i > offset {
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return *ss[i-offset]
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}
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return ""
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}
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func f8(ss []*string, i int) string {
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const offset = 3<<29 + 10
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if i > offset {
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return *ss[i-offset]
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}
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return ""
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}
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func f9(ss []*string, i int) string {
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const offset = 3<<29 - 10
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if i > offset {
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return *ss[i-offset]
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}
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return ""
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}
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