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go/test/checkbce.go
Keith Randall 73f92f9b04 cmd/compile: use len(s)<=cap(s) to remove more bounds checks
When we discover a relation x <= len(s), also discover the relation
x <= cap(s).  That way, in situations like:

a := s[x:]  // tests 0 <= x <= len(s)
b := s[:x]  // tests 0 <= x <= cap(s)

the second check can be eliminated.

Fixes #16813

Change-Id: Ifc037920b6955e43bac1a1eaf6bac63a89cfbd44
Reviewed-on: https://go-review.googlesource.com/33633
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
Reviewed-by: David Chase <drchase@google.com>
2017-02-02 17:45:58 +00:00

117 lines
2.3 KiB
Go

// +build amd64
// errorcheck -0 -d=ssa/check_bce/debug=3
package main
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) {
useInt(a[i]) // ERROR "Found IsInBounds$"
useInt(a[i%256]) // ERROR "Found IsInBounds$"
useInt(a[i&255])
useInt(a[i&17])
if 4 <= i && i < len(a) {
useInt(a[i])
useInt(a[i-1]) // ERROR "Found IsInBounds$"
// TODO: 'if 4 <= i && i < len(a)' gets rewritten to 'if uint(i - 4) < 256 - 4',
// which the bounds checker cannot yet use to infer that the next line doesn't need a bounds check.
useInt(a[i-4])
}
}
func f2(a [256]int, i uint) {
useInt(a[i]) // ERROR "Found IsInBounds$"
useInt(a[i%256])
useInt(a[i&255])
useInt(a[i&17])
}
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$"
}
}
//go:noinline
func useInt(a int) {
}
//go:noinline
func useSlice(a []int) {
}
func main() {
}