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master
test/fixedbugs/issue21655.go
62 строки
1 KB
Keith Randall
cmd/compile: fix large load/store offsets on 386
08 дек 2017, 06:53
08 дек 2017, 06:53
4c800f0
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// compile // Copyright 2017 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. // Make sure assembly offsets don't get too large. // To trigger issue21655, the index offset needs to be small // enough to fit into an int32 (to get rewritten to an ADDQconst) // but large enough to overflow an int32 after multiplying by the stride. package main func f1(a []int64, i int64) int64 { return a[i+1<<30] } func f2(a []int32, i int64) int32 { return a[i+1<<30] } func f3(a []int16, i int64) int16 { return a[i+1<<30] } func f4(a []int8, i int64) int8 { return a[i+1<<31] } func f5(a []float64, i int64) float64 { return a[i+1<<30] } func f6(a []float32, i int64) float32 { return a[i+1<<30] } // Note: Before the fix for issue 21655, f{1,2,5,6} made // the compiler crash. f3 silently generated the wrong // code, using an offset of -1<<31 instead of 1<<31. // (This is due to the assembler accepting offsets // like 0x80000000 and silently using them as // signed 32 bit offsets.) // f4 was ok, but testing it can't hurt. func f7(ss []*string, i int) string { const offset = 3 << 29 // 3<<29 * 4 = 3<<31 = 1<<31 mod 1<<32. if i > offset { return *ss[i-offset] } return "" } func f8(ss []*string, i int) string { const offset = 3<<29 + 10 if i > offset { return *ss[i-offset] } return "" } func f9(ss []*string, i int) string { const offset = 3<<29 - 10 if i > offset { return *ss[i-offset] } return "" }