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go/test/checkbce.go
Keith Randall 4a9064ef41 cmd/compile: fix ordering for short-circuiting ops
Make sure the side effects inside short-circuited operations (&& and ||)
happen correctly.

Before this CL, we attached the side effects to the node itself using
exprInPlace. That caused other side effects in sibling expressions
to get reordered with respect to the short circuit side effect.

Instead, rewrite a && b like:

r := a
if r {
  r = b
}

That code we can keep correctly ordered with respect to other
side-effects extracted from part of a big expression.

exprInPlace seems generally unsafe. But this was the only case where
exprInPlace is called not at the top level of an expression, so I
don't think the other uses can actually trigger an issue (there can't
be a sibling expression). TODO: maybe those cases don't need "in
place", and we can retire that function generally.

This CL needed a small tweak to the SSA generation of OIF so that the
short circuit optimization still triggers. The short circuit optimization
looks for triangle but not diamonds, so don't bother allocating a block
if it will be empty.

Go 1 benchmarks are in the noise.

Fixes #30566

Change-Id: I19c04296bea63cbd6ad05f87a63b005029123610
Reviewed-on: https://go-review.googlesource.com/c/go/+/165617
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
2019-03-06 20:04:07 +00:00

182 lines
3.6 KiB
Go

// +build amd64,!gcflags_noopt
// errorcheck -0 -d=ssa/check_bce/debug=3
// Copyright 2016 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.
// Test that the compiler does bounds check elimination as expected.
// This avoids accidental regressions.
package main
import "encoding/binary"
func f0(a []int) {
a[0] = 1 // ERROR "Found IsInBounds$"
a[0] = 1
a[6] = 1 // ERROR "Found IsInBounds$"
a[6] = 1
a[5] = 1
a[5] = 1
}
func f1(a [256]int, i int) {
var j int
useInt(a[i]) // ERROR "Found IsInBounds$"
j = i % 256
useInt(a[j]) // ERROR "Found IsInBounds$"
j = i & 255
useInt(a[j])
j = i & 17
useInt(a[j])
if 4 <= i && i < len(a) {
useInt(a[i])
useInt(a[i-1])
useInt(a[i-4])
}
}
func f2(a [256]int, i uint) {
useInt(a[i]) // ERROR "Found IsInBounds$"
j := i % 256
useInt(a[j])
j = i & 255
useInt(a[j])
j = i & 17
useInt(a[j])
}
func f2a(a [35]int, i uint8) {
useInt(a[i]) // ERROR "Found IsInBounds$"
j := i & 34
useInt(a[j])
j = i & 17
useInt(a[j])
}
func f2b(a [35]int, i uint16) {
useInt(a[i]) // ERROR "Found IsInBounds$"
j := i & 34
useInt(a[j])
j = i & 17
useInt(a[j])
}
func f2c(a [35]int, i uint32) {
useInt(a[i]) // ERROR "Found IsInBounds$"
j := i & 34
useInt(a[j])
j = i & 17
useInt(a[j])
}
func f3(a [256]int, i uint8) {
useInt(a[i])
useInt(a[i+10])
useInt(a[i+14])
}
func f4(a [27]int, i uint8) {
useInt(a[i%15])
useInt(a[i%19])
useInt(a[i%27])
}
func f5(a []int) {
if len(a) > 5 {
useInt(a[5])
useSlice(a[6:])
useSlice(a[:6])
}
}
func f6(a [32]int, b [64]int, i int) {
useInt(a[uint32(i*0x07C4ACDD)>>27])
useInt(b[uint64(i*0x07C4ACDD)>>58])
useInt(a[uint(i*0x07C4ACDD)>>59])
// The following bounds should not be removed because they can overflow.
useInt(a[uint32(i*0x106297f105d0cc86)>>26]) // ERROR "Found IsInBounds$"
useInt(b[uint64(i*0x106297f105d0cc86)>>57]) // ERROR "Found IsInBounds$"
useInt(a[int32(i*0x106297f105d0cc86)>>26]) // ERROR "Found IsInBounds$"
useInt(b[int64(i*0x106297f105d0cc86)>>57]) // ERROR "Found IsInBounds$"
}
func g1(a []int) {
for i := range a {
a[i] = i
useSlice(a[:i+1])
useSlice(a[:i])
}
}
func g2(a []int) {
useInt(a[3]) // ERROR "Found IsInBounds$"
useInt(a[2])
useInt(a[1])
useInt(a[0])
}
func g3(a []int) {
for i := range a[:256] { // ERROR "Found IsSliceInBounds$"
useInt(a[i]) // ERROR "Found IsInBounds$"
}
b := a[:256]
for i := range b {
useInt(b[i])
}
}
func g4(a [100]int) {
for i := 10; i < 50; i++ {
useInt(a[i-10])
useInt(a[i])
useInt(a[i+25])
useInt(a[i+50])
// The following are out of bounds.
useInt(a[i-11]) // ERROR "Found IsInBounds$"
useInt(a[i+51]) // ERROR "Found IsInBounds$"
}
}
func decode1(data []byte) (x uint64) {
for len(data) >= 32 {
x += binary.BigEndian.Uint64(data[:8])
x += binary.BigEndian.Uint64(data[8:16])
x += binary.BigEndian.Uint64(data[16:24])
x += binary.BigEndian.Uint64(data[24:32])
data = data[32:]
}
return x
}
func decode2(data []byte) (x uint64) {
// TODO(rasky): this should behave like decode1 and compile to no
// boundchecks. We're currently not able to remove all of them.
for len(data) >= 32 {
x += binary.BigEndian.Uint64(data)
data = data[8:]
x += binary.BigEndian.Uint64(data) // ERROR "Found IsInBounds$"
data = data[8:]
x += binary.BigEndian.Uint64(data) // ERROR "Found IsInBounds$"
data = data[8:]
x += binary.BigEndian.Uint64(data) // ERROR "Found IsInBounds$"
data = data[8:]
}
return x
}
//go:noinline
func useInt(a int) {
}
//go:noinline
func useSlice(a []int) {
}
func main() {
}