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[dev.simd] cmd/compile: improve slicemask removal

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this will be subsumed by pending changes in local slice
representation, however this was easy and works well.

Change-Id: I5b6eb10d257f04f906be7a8a6f2b6833992a39e8
Reviewed-on: https://go-review.googlesource.com/c/go/+/704876
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
This commit is contained in:
David Chase 2025-09-17 17:21:37 -04:00
parent 2b50ffe172
commit 8e60feeb41
2 changed files with 81 additions and 67 deletions
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30
src/cmd/compile/internal/ssa/prove.go
View file

@ -2529,24 +2529,38 @@ func simplifyBlock(sdom SparseTree, ft *factsTable, b *Block) {
switch v.Op {
case OpSlicemask:
// Replace OpSlicemask operations in b with constants where possible.
x, delta := isConstDelta(v.Args[0])
if x == nil {
cap := v.Args[0]
x, delta := isConstDelta(cap)
if x != nil {
// slicemask(x + y)
// if x is larger than -y (y is negative), then slicemask is -1.
lim := ft.limits[x.ID]
if lim.umin > uint64(-delta) {
if cap.Op == OpAdd64 {
v.reset(OpConst64)
} else {
v.reset(OpConst32)
}
if b.Func.pass.debug > 0 {
b.Func.Warnl(v.Pos, "Proved slicemask not needed")
}
v.AuxInt = -1
}
break
}
// slicemask(x + y)
// if x is larger than -y (y is negative), then slicemask is -1.
lim := ft.limits[x.ID]
if lim.umin > uint64(-delta) {
if v.Args[0].Op == OpAdd64 {
lim := ft.limits[cap.ID]
if lim.umin > 0 {
if cap.Type.Size() == 8 {
v.reset(OpConst64)
} else {
v.reset(OpConst32)
}
if b.Func.pass.debug > 0 {
b.Func.Warnl(v.Pos, "Proved slicemask not needed")
b.Func.Warnl(v.Pos, "Proved slicemask not needed (by limit)")
}
v.AuxInt = -1
}
case OpCtz8, OpCtz16, OpCtz32, OpCtz64:
// On some architectures, notably amd64, we can generate much better
// code for CtzNN if we know that the argument is non-zero.

118
test/loopbce.go
View file

@ -9,7 +9,7 @@ import "math"
func f0a(a []int) int {
x := 0
for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
x += a[i] // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += a[i] // ERROR "Proved IsInBounds$"
}
return x
}
@ -17,7 +17,7 @@ func f0a(a []int) int {
func f0b(a []int) int {
x := 0
for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
b := a[i:] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
b := a[i:] // ERROR "Proved IsSliceInBounds$"
x += b[0]
}
return x
@ -26,8 +26,8 @@ func f0b(a []int) int {
func f0c(a []int) int {
x := 0
for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
b := a[:i+1] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
x += b[0] // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
b := a[:i+1] // ERROR "Proved IsSliceInBounds$"
x += b[0] // ERROR "Proved IsInBounds$"
}
return x
}
@ -43,7 +43,7 @@ func f1(a []int) int {
func f2(a []int) int {
x := 0
for i := 1; i < len(a); i++ { // ERROR "Induction variable: limits \[1,\?\), increment 1$"
x += a[i] // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += a[i] // ERROR "Proved IsInBounds$"
}
return x
}
@ -51,7 +51,7 @@ func f2(a []int) int {
func f4(a [10]int) int {
x := 0
for i := 0; i < len(a); i += 2 { // ERROR "Induction variable: limits \[0,8\], increment 2$"
x += a[i] // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += a[i] // ERROR "Proved IsInBounds$"
}
return x
}
@ -91,7 +91,7 @@ func f5_int8(a [10]int) int {
//go:noinline
func f6(a []int) {
for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
b := a[0:i] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
b := a[0:i] // ERROR "Proved IsSliceInBounds$"
f6(b)
}
}
@ -99,7 +99,7 @@ func f6(a []int) {
func g0a(a string) int {
x := 0
for i := 0; i < len(a); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
x += int(a[i]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -107,7 +107,7 @@ func g0a(a string) int {
func g0b(a string) int {
x := 0
for i := 0; len(a) > i; i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
x += int(a[i]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -115,7 +115,7 @@ func g0b(a string) int {
func g0c(a string) int {
x := 0
for i := len(a); i > 0; i-- { // ERROR "Induction variable: limits \(0,\?\], increment 1$"
x += int(a[i-1]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i-1]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -123,7 +123,7 @@ func g0c(a string) int {
func g0d(a string) int {
x := 0
for i := len(a); 0 < i; i-- { // ERROR "Induction variable: limits \(0,\?\], increment 1$"
x += int(a[i-1]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i-1]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -131,7 +131,7 @@ func g0d(a string) int {
func g0e(a string) int {
x := 0
for i := len(a) - 1; i >= 0; i-- { // ERROR "Induction variable: limits \[0,\?\], increment 1$"
x += int(a[i]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -139,7 +139,7 @@ func g0e(a string) int {
func g0f(a string) int {
x := 0
for i := len(a) - 1; 0 <= i; i-- { // ERROR "Induction variable: limits \[0,\?\], increment 1$"
x += int(a[i]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -148,7 +148,7 @@ func g1() int {
a := "evenlength"
x := 0
for i := 0; i < len(a); i += 2 { // ERROR "Induction variable: limits \[0,8\], increment 2$"
x += int(a[i]) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
x += int(a[i]) // ERROR "Proved IsInBounds$"
}
return x
}
@ -158,7 +158,7 @@ func g2() int {
x := 0
for i := 0; i < len(a); i += 2 { // ERROR "Induction variable: limits \[0,8\], increment 2$"
j := i
if a[i] == 'e' { // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
if a[i] == 'e' { // ERROR "Proved IsInBounds$"
j = j + 1
}
x += int(a[j])
@ -169,29 +169,29 @@ func g2() int {
func g3a() {
a := "this string has length 25"
for i := 0; i < len(a); i += 5 { // ERROR "Induction variable: limits \[0,20\], increment 5$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[:i+3]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[:i+5]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[i:]) // ERROR "Proved IsSliceInBounds$" "Proved slicemask not needed \(by limit\)$"
useString(a[:i+3]) // ERROR "Proved IsSliceInBounds$"
useString(a[:i+5]) // ERROR "Proved IsSliceInBounds$"
useString(a[:i+6])
}
}
func g3b(a string) {
for i := 0; i < len(a); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i+1:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[i+1:]) // ERROR "Proved IsSliceInBounds$"
}
}
func g3c(a string) {
for i := 0; i < len(a); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[:i+1]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[:i+1]) // ERROR "Proved IsSliceInBounds$"
}
}
func h1(a []byte) {
c := a[:128]
for i := range c { // ERROR "Induction variable: limits \[0,128\), increment 1$"
c[i] = byte(i) // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
c[i] = byte(i) // ERROR "Proved IsInBounds$"
}
}
@ -208,11 +208,11 @@ func k0(a [100]int) [100]int {
continue
}
a[i-11] = i
a[i-10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i-5] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+5] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i-10] = i // ERROR "Proved IsInBounds$"
a[i-5] = i // ERROR "Proved IsInBounds$"
a[i] = i // ERROR "Proved IsInBounds$"
a[i+5] = i // ERROR "Proved IsInBounds$"
a[i+10] = i // ERROR "Proved IsInBounds$"
a[i+11] = i
}
return a
@ -225,12 +225,12 @@ func k1(a [100]int) [100]int {
continue
}
useSlice(a[:i-11])
useSlice(a[:i-10]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[:i-5]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[:i]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[:i+5]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[:i+10]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[:i+11]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[:i-10]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[:i-5]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[:i]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[:i+5]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[:i+10]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[:i+11]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[:i+12])
}
@ -243,13 +243,13 @@ func k2(a [100]int) [100]int {
// This is a trick to prohibit sccp to optimize out the following out of bound check
continue
}
useSlice(a[i-11:])
useSlice(a[i-10:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[i-5:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[i+5:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[i+10:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[i+11:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useSlice(a[i-11:]) // ERROR "Proved slicemask not needed \(by limit\)$"
useSlice(a[i-10:]) // ERROR "Proved IsSliceInBounds$" "Proved slicemask not needed \(by limit\)$"
useSlice(a[i-5:]) // ERROR "Proved IsSliceInBounds$" "Proved slicemask not needed \(by limit\)$"
useSlice(a[i:]) // ERROR "Proved IsSliceInBounds$" "Proved slicemask not needed \(by limit\)$"
useSlice(a[i+5:]) // ERROR "Proved IsSliceInBounds$" "Proved slicemask not needed \(by limit\)$"
useSlice(a[i+10:]) // ERROR "Proved IsSliceInBounds$" "Proved slicemask not needed \(by limit\)$"
useSlice(a[i+11:]) // ERROR "Proved IsSliceInBounds$"
useSlice(a[i+12:])
}
return a
@ -262,7 +262,7 @@ func k3(a [100]int) [100]int {
continue
}
a[i+9] = i
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+10] = i // ERROR "Proved IsInBounds$"
a[i+11] = i
}
return a
@ -275,7 +275,7 @@ func k3neg(a [100]int) [100]int {
continue
}
a[i+9] = i
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+10] = i // ERROR "Proved IsInBounds$"
a[i+11] = i
}
return a
@ -288,7 +288,7 @@ func k3neg2(a [100]int) [100]int {
continue
}
a[i+9] = i
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+10] = i // ERROR "Proved IsInBounds$"
a[i+11] = i
}
return a
@ -299,7 +299,7 @@ func k4(a [100]int) [100]int {
// and it isn't worth adding that special case to prove.
min := (-1)<<63 + 1
for i := min; i < min+50; i++ { // ERROR "Induction variable: limits \[-9223372036854775807,-9223372036854775757\), increment 1$"
a[i-min] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i-min] = i // ERROR "Proved IsInBounds$"
}
return a
}
@ -307,8 +307,8 @@ func k4(a [100]int) [100]int {
func k5(a [100]int) [100]int {
max := (1 << 63) - 1
for i := max - 50; i < max; i++ { // ERROR "Induction variable: limits \[9223372036854775757,9223372036854775807\), increment 1$"
a[i-max+50] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i-(max-70)] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i-max+50] = i // ERROR "Proved IsInBounds$"
a[i-(max-70)] = i // ERROR "Proved IsInBounds$"
}
return a
}
@ -374,22 +374,22 @@ func d4() {
}
func d5() {
for i := int64(math.MinInt64 + 9); i > math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775803,-9223372036854775799\], increment 4"
for i := int64(math.MinInt64 + 9); i > math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775803,-9223372036854775799\], increment 4$"
useString("foo")
}
for i := int64(math.MinInt64 + 8); i > math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775804,-9223372036854775800\], increment 4"
for i := int64(math.MinInt64 + 8); i > math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775804,-9223372036854775800\], increment 4$"
useString("foo")
}
for i := int64(math.MinInt64 + 7); i > math.MinInt64+2; i -= 4 {
useString("foo")
}
for i := int64(math.MinInt64 + 6); i > math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775802,-9223372036854775802\], increment 4"
for i := int64(math.MinInt64 + 6); i > math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775802,-9223372036854775802\], increment 4$"
useString("foo")
}
for i := int64(math.MinInt64 + 9); i >= math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775803,-9223372036854775799\], increment 4"
for i := int64(math.MinInt64 + 9); i >= math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775803,-9223372036854775799\], increment 4$"
useString("foo")
}
for i := int64(math.MinInt64 + 8); i >= math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775804,-9223372036854775800\], increment 4"
for i := int64(math.MinInt64 + 8); i >= math.MinInt64+2; i -= 4 { // ERROR "Induction variable: limits \[-9223372036854775804,-9223372036854775800\], increment 4$"
useString("foo")
}
for i := int64(math.MinInt64 + 7); i >= math.MinInt64+2; i -= 4 {
@ -410,23 +410,23 @@ func bce1() {
panic("invalid test: modulos should differ")
}
for i := b; i < a; i += z { // ERROR "Induction variable: limits \[-1547,9223372036854772720\], increment 1337"
for i := b; i < a; i += z { // ERROR "Induction variable: limits \[-1547,9223372036854772720\], increment 1337$"
useString("foobar")
}
}
func nobce2(a string) {
for i := int64(0); i < int64(len(a)); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[i:]) // ERROR "Proved IsSliceInBounds$"
}
for i := int64(0); i < int64(len(a))-31337; i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
useString(a[i:]) // ERROR "Proved IsSliceInBounds$"
}
for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$" "Disproved Less64"
for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Disproved Less64$" "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:])
}
j := int64(len(a)) - 123
for i := int64(0); i < j+123+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$" "Disproved Less64"
for i := int64(0); i < j+123+int64(-1<<63); i++ { // ERROR "Disproved Less64$" "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:])
}
for i := int64(0); i < j+122+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
@ -455,16 +455,16 @@ func issue26116a(a []int) {
func stride1(x *[7]int) int {
s := 0
for i := 0; i <= 8; i += 3 { // ERROR "Induction variable: limits \[0,6\], increment 3"
s += x[i] // ERROR "Proved IsInBounds"
for i := 0; i <= 8; i += 3 { // ERROR "Induction variable: limits \[0,6\], increment 3$"
s += x[i] // ERROR "Proved IsInBounds$"
}
return s
}
func stride2(x *[7]int) int {
s := 0
for i := 0; i < 9; i += 3 { // ERROR "Induction variable: limits \[0,6\], increment 3"
s += x[i] // ERROR "Proved IsInBounds"
for i := 0; i < 9; i += 3 { // ERROR "Induction variable: limits \[0,6\], increment 3$"
s += x[i] // ERROR "Proved IsInBounds$"
}
return s
}