go/test/fixedbugs/issue19137.go

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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.
// Issue 19137: folding address into load/store causes
// odd offset on ARM64.
package p
type T struct {
p *int
a [2]byte
b [6]byte // not 4-byte aligned
}
func f(b [6]byte) T {
var x [1000]int // a large stack frame
_ = x
return T{b: b}
}
cmd/compile: do not fold offset into load/store for args on ARM64 Args may be not at 8-byte aligned offset to SP. When the stack frame is large, folding the offset of args may cause large unaligned offsets that does not fit in a machine instruction on ARM64. Therefore disable folding offsets for args. This has small performance impact (see below). A better fix would be letting the assembler backend fix up the offset by loading it into a register if it doesn't fit into an instruction. And the compiler can simply generate large load/stores with offset. Since in most of the cases the offset is aligned or the stack frame is small, it can fit in an instruction and no fixup is needed. But this is too complicated for Go 1.8. name old time/op new time/op delta BinaryTree17-8 8.30s ± 0% 8.31s ± 0% ~ (p=0.579 n=10+10) Fannkuch11-8 6.14s ± 0% 6.18s ± 0% +0.53% (p=0.000 n=9+10) FmtFprintfEmpty-8 117ns ± 0% 117ns ± 0% ~ (all equal) FmtFprintfString-8 196ns ± 0% 197ns ± 0% +0.72% (p=0.000 n=10+10) FmtFprintfInt-8 204ns ± 0% 205ns ± 0% +0.49% (p=0.000 n=9+10) FmtFprintfIntInt-8 302ns ± 0% 307ns ± 1% +1.46% (p=0.000 n=10+10) FmtFprintfPrefixedInt-8 329ns ± 2% 326ns ± 0% ~ (p=0.083 n=10+10) FmtFprintfFloat-8 540ns ± 0% 542ns ± 0% +0.46% (p=0.000 n=8+7) FmtManyArgs-8 1.20µs ± 1% 1.19µs ± 1% -1.02% (p=0.000 n=10+10) GobDecode-8 17.3ms ± 1% 17.8ms ± 0% +2.75% (p=0.000 n=10+7) GobEncode-8 15.3ms ± 1% 15.4ms ± 0% +0.57% (p=0.004 n=9+10) Gzip-8 789ms ± 0% 803ms ± 0% +1.78% (p=0.000 n=9+10) Gunzip-8 128ms ± 0% 130ms ± 0% +1.73% (p=0.000 n=10+9) HTTPClientServer-8 202µs ± 6% 201µs ±10% ~ (p=0.739 n=10+10) JSONEncode-8 42.0ms ± 0% 42.1ms ± 0% +0.19% (p=0.028 n=10+9) JSONDecode-8 159ms ± 0% 161ms ± 0% +1.05% (p=0.000 n=9+10) Mandelbrot200-8 10.1ms ± 0% 10.1ms ± 0% -0.07% (p=0.000 n=10+9) GoParse-8 8.46ms ± 1% 8.61ms ± 1% +1.77% (p=0.000 n=10+10) RegexpMatchEasy0_32-8 227ns ± 1% 226ns ± 0% -0.35% (p=0.001 n=10+9) RegexpMatchEasy0_1K-8 1.63µs ± 0% 1.63µs ± 0% -0.13% (p=0.000 n=10+9) RegexpMatchEasy1_32-8 250ns ± 0% 249ns ± 0% -0.40% (p=0.001 n=8+9) RegexpMatchEasy1_1K-8 2.07µs ± 0% 2.08µs ± 0% +0.05% (p=0.027 n=9+9) RegexpMatchMedium_32-8 350ns ± 0% 350ns ± 0% ~ (p=0.412 n=9+8) RegexpMatchMedium_1K-8 104µs ± 0% 104µs ± 0% +0.31% (p=0.000 n=10+7) RegexpMatchHard_32-8 5.82µs ± 0% 5.82µs ± 0% ~ (p=0.937 n=9+9) RegexpMatchHard_1K-8 176µs ± 0% 176µs ± 0% +0.03% (p=0.000 n=9+8) Revcomp-8 1.36s ± 1% 1.37s ± 1% ~ (p=0.218 n=10+10) Template-8 151ms ± 1% 156ms ± 1% +3.21% (p=0.000 n=10+10) TimeParse-8 737ns ± 0% 758ns ± 2% +2.74% (p=0.000 n=10+10) TimeFormat-8 801ns ± 2% 789ns ± 1% -1.51% (p=0.000 n=10+10) [Geo mean] 142µs 143µs +0.50% Fixes #19137. Change-Id: Ib8a21ea98c0ffb2d282a586535b213cc163e1b67 Reviewed-on: https://go-review.googlesource.com/37251 Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
2017-02-19 02:03:15 +00:00
// Arg symbol's base address may be not at an aligned offset to
// SP. Folding arg's address into load/store may cause odd offset.
func move(a, b [20]byte) [20]byte {
var x [1000]int // a large stack frame
_ = x
return b // b is not 8-byte aligned to SP
}
func zero() ([20]byte, [20]byte) {
var x [1000]int // a large stack frame
_ = x
return [20]byte{}, [20]byte{} // the second return value is not 8-byte aligned to SP
}
// Issue 21992: unaligned offset between 256 and 504 and handled
// incorrectly.
type T2 struct {
a [257]byte
// fields below are not 8-, 4-, 2-byte aligned
b [8]byte
c [4]byte
d [2]byte
}
func f2(x *T2) {
x.b = [8]byte{}
x.c = [4]byte{}
x.d = [2]byte{}
}