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cmd/compile: bce when max and limit are consts

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Removes 49 more bound checks in make.bash. For example:

var a[100]int
for i := 0; i < 50; i++ {
  use a[i+25]
}

Change-Id: I85e0130ee5d07f0ece9b17044bba1a2047414ce7
Reviewed-on: https://go-review.googlesource.com/21379
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Alexandru Moșoi 2016-04-01 15:09:19 +02:00 committed by Alexandru Moșoi
parent 00681eec6a
commit 6c6089b3fd
3 changed files with 132 additions and 1 deletions
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41
src/cmd/compile/internal/ssa/loopbce.go
View File

@ -240,6 +240,37 @@ func removeBoundsChecks(f *Func, sdom sparseTree, m map[*Value]indVar) {
}
skip2:
// Simplify
// (IsInBounds (Add64 ind) (Const64 [c])) where 0 <= min <= ind < max <= (Const64 [c])
// (IsSliceInBounds ind (Const64 [c])) where 0 <= min <= ind < max <= (Const64 [c])
if v.Op == OpIsInBounds || v.Op == OpIsSliceInBounds {
ind, add := dropAdd64(v.Args[0])
if ind.Op != OpPhi {
goto skip3
}
// ind + add >= 0 <-> min + add >= 0 <-> min >= -add
if iv, has := m[ind]; has && sdom.isAncestorEq(iv.entry, b) && isGreaterOrEqualThan(iv.min, -add) {
if !v.Args[1].isGenericIntConst() || !iv.max.isGenericIntConst() {
goto skip3
}
limit := v.Args[1].AuxInt
if v.Op == OpIsSliceInBounds {
// If limit++ overflows signed integer then 0 <= max && max <= limit will be false.
limit++
}
if max := iv.max.AuxInt + add; 0 <= max && max <= limit { // handle overflow
if f.pass.debug > 0 {
f.Config.Warnl(b.Line, "Found redundant (%s ind %d), ind < %d", v.Op, v.Args[1].AuxInt, iv.max.AuxInt+add)
}
goto simplify
}
}
}
skip3:
continue
simplify:
@ -258,3 +289,13 @@ func dropAdd64(v *Value) (*Value, int64) {
}
return v, 0
}
func isGreaterOrEqualThan(v *Value, c int64) bool {
if c == 0 {
return isNonNegative(v)
}
if v.isGenericIntConst() && v.AuxInt >= c {
return true
}
return false
}

15
test/checkbce.go
View File

@ -57,7 +57,7 @@ func f6(a [32]int, b [64]int, i int) {
useInt(b[uint64(i*0x07C4ACDD)>>58])
useInt(a[uint(i*0x07C4ACDD)>>59])
// The following bounds should removed as they can overflow.
// 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$"
@ -89,6 +89,19 @@ func g3(a []int) {
}
}
func g4(a [100]int) {
for i := 10; i < 50; i++ {
useInt(a[i-10])
useInt(a[i])
useInt(a[i+25])
useInt(a[i+50])
// The following are out of bounds.
useInt(a[i-11]) // ERROR "Found IsInBounds$"
useInt(a[i+51]) // ERROR "Found IsInBounds$"
}
}
//go:noinline
func useInt(a int) {
}

77
test/loopbce.go
View File

@ -139,6 +139,70 @@ func h2(a []byte) {
}
}
func k0(a [100]int) [100]int {
for i := 10; i < 90; i++ { // ERROR "Induction variable with minimum 10 and increment 1$"
a[i-11] = i
a[i-10] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 80$"
a[i-5] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 85$"
a[i] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 90$"
a[i+5] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 95$"
a[i+10] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 100$"
a[i+11] = i
}
return a
}
func k1(a [100]int) [100]int {
for i := 10; i < 90; i++ { // ERROR "Induction variable with minimum 10 and increment 1$"
useSlice(a[:i-11])
useSlice(a[:i-10]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 80$"
useSlice(a[:i-5]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 85$"
useSlice(a[:i]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 90$"
useSlice(a[:i+5]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 95$"
useSlice(a[:i+10]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 100$"
useSlice(a[:i+11]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 101$"
}
return a
}
func k2(a [100]int) [100]int {
for i := 10; i < 90; i++ { // ERROR "Induction variable with minimum 10 and increment 1$"
useSlice(a[i-11:])
useSlice(a[i-10:]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 80$"
useSlice(a[i-5:]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 85$"
useSlice(a[i:]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 90$"
useSlice(a[i+5:]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 95$"
useSlice(a[i+10:]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 100$"
useSlice(a[i+11:]) // ERROR "Found redundant \(IsSliceInBounds ind 100\), ind < 101$"
}
return a
}
func k3(a [100]int) [100]int {
for i := -10; i < 90; i++ { // ERROR "Induction variable with minimum -10 and increment 1$"
a[i+10] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 100$"
}
return a
}
func k4(a [100]int) [100]int {
min := (-1) << 63
for i := min; i < min+50; i++ { // ERROR "Induction variable with minimum -9223372036854775808 and increment 1$"
a[i-min] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 50$"
}
return a
}
func k5(a [100]int) [100]int {
max := (1 << 63) - 1
for i := max - 50; i < max; i++ { // ERROR "Induction variable with minimum 9223372036854775757 and increment 1$"
a[i-max+50] = i
a[i-(max-70)] = i // ERROR "Found redundant \(IsInBounds ind 100\), ind < 70$"
}
return a
}
func nobce1() {
// tests overflow of max-min
a := int64(9223372036854774057)
@ -168,9 +232,22 @@ func nobce2(a string) {
}
}
func nobce3(a [100]int64) [100]int64 {
min := int64((-1) << 63)
max := int64((1 << 63) - 1)
for i := min; i < max; i++ { // ERROR "Induction variable with minimum -9223372036854775808 and increment 1$"
a[i] = i
}
return a
}
//go:noinline
func useString(a string) {
}
//go:noinline
func useSlice(a []int) {
}
func main() {
}