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go/test/loopbce.go
Keith Randall af7f067e0d cmd/compile: tighten bounds for induction variables in strided loops 
for i := 0; i < 9; i += 3

Currently we compute bounds of [0,8]. Really we know that it is [0,6].

CL 415874 computed the better bound as part of overflow detection.
This CL just incorporates that better info to the prove pass.

R=go1.20

Change-Id: Ife82cc415321f6652c2b5d132a40ec23e3385766
Reviewed-on: https://go-review.googlesource.com/c/go/+/415937
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
2022-08-31 22:04:55 +00:00

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// +build amd64
// errorcheck -0 -d=ssa/prove/debug=1
package main
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$"
}
return x
}
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$"
x += b[0]
}
return x
}
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]
}
return x
}
func f1(a []int) int {
x := 0
for _, i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
x += i
}
return x
}
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$"
}
return x
}
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$"
}
return x
}
func f5(a [10]int) int {
x := 0
for i := -10; i < len(a); i += 2 { // ERROR "Induction variable: limits \[-10,8\], increment 2$"
x += a[i]
}
return x
}
func f6(a []int) {
for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
b := a[0:i] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
f6(b)
}
}
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$"
}
return x
}
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$"
}
return x
}
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$"
}
return x
}
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$"
}
return x
}
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$"
}
return x
}
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$"
}
return x
}
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$"
}
return x
}
func g2() int {
a := "evenlength"
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$"
j = j + 1
}
x += int(a[j])
}
return x
}
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+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$"
}
}
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$"
}
}
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$"
}
}
func h2(a []byte) {
for i := range a[:128] { // ERROR "Induction variable: limits \[0,128\), increment 1$"
a[i] = byte(i)
}
}
func k0(a [100]int) [100]int {
for i := 10; i < 90; i++ { // ERROR "Induction variable: limits \[10,90\), increment 1$"
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+11] = i
}
return a
}
func k1(a [100]int) [100]int {
for i := 10; i < 90; i++ { // ERROR "Induction variable: limits \[10,90\), increment 1$"
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+12])
}
return a
}
func k2(a [100]int) [100]int {
for i := 10; i < 90; i++ { // ERROR "Induction variable: limits \[10,90\), increment 1$"
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+12:])
}
return a
}
func k3(a [100]int) [100]int {
for i := -10; i < 90; i++ { // ERROR "Induction variable: limits \[-10,90\), increment 1$"
a[i+9] = i
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+11] = i
}
return a
}
func k3neg(a [100]int) [100]int {
for i := 89; i > -11; i-- { // ERROR "Induction variable: limits \(-11,89\], increment 1$"
a[i+9] = i
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+11] = i
}
return a
}
func k3neg2(a [100]int) [100]int {
for i := 89; i >= -10; i-- { // ERROR "Induction variable: limits \[-10,89\], increment 1$"
a[i+9] = i
a[i+10] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
a[i+11] = i
}
return a
}
func k4(a [100]int) [100]int {
min := (-1) << 63
for i := min; i < min+50; i++ { // ERROR "Induction variable: limits \[-9223372036854775808,-9223372036854775758\), increment 1$"
a[i-min] = i // ERROR "(\([0-9]+\) )?Proved IsInBounds$"
}
return a
}
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$"
}
return a
}
func d1(a [100]int) [100]int {
for i := 0; i < 100; i++ { // ERROR "Induction variable: limits \[0,100\), increment 1$"
for j := 0; j < i; j++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
a[j] = 0 // ERROR "Proved IsInBounds$"
a[j+1] = 0 // FIXME: this boundcheck should be eliminated
a[j+2] = 0
}
}
return a
}
func d2(a [100]int) [100]int {
for i := 0; i < 100; i++ { // ERROR "Induction variable: limits \[0,100\), increment 1$"
for j := 0; i > j; j++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
a[j] = 0 // ERROR "Proved IsInBounds$"
a[j+1] = 0 // FIXME: this boundcheck should be eliminated
a[j+2] = 0
}
}
return a
}
func d3(a [100]int) [100]int {
for i := 0; i <= 99; i++ { // ERROR "Induction variable: limits \[0,99\], increment 1$"
for j := 0; j <= i-1; j++ {
a[j] = 0
a[j+1] = 0 // ERROR "Proved IsInBounds$"
a[j+2] = 0
}
}
return a
}
func d4() {
for i := int64(math.MaxInt64 - 9); i < math.MaxInt64-2; i += 4 { // ERROR "Induction variable: limits \[9223372036854775798,9223372036854775802\], increment 4$"
useString("foo")
}
for i := int64(math.MaxInt64 - 8); i < math.MaxInt64-2; i += 4 { // ERROR "Induction variable: limits \[9223372036854775799,9223372036854775803\], increment 4$"
useString("foo")
}
for i := int64(math.MaxInt64 - 7); i < math.MaxInt64-2; i += 4 {
useString("foo")
}
for i := int64(math.MaxInt64 - 6); i < math.MaxInt64-2; i += 4 { // ERROR "Induction variable: limits \[9223372036854775801,9223372036854775801\], increment 4$"
useString("foo")
}
for i := int64(math.MaxInt64 - 9); i <= math.MaxInt64-2; i += 4 { // ERROR "Induction variable: limits \[9223372036854775798,9223372036854775802\], increment 4$"
useString("foo")
}
for i := int64(math.MaxInt64 - 8); i <= math.MaxInt64-2; i += 4 { // ERROR "Induction variable: limits \[9223372036854775799,9223372036854775803\], increment 4$"
useString("foo")
}
for i := int64(math.MaxInt64 - 7); i <= math.MaxInt64-2; i += 4 {
useString("foo")
}
for i := int64(math.MaxInt64 - 6); i <= math.MaxInt64-2; i += 4 {
useString("foo")
}
}
func d5() {
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"
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"
useString("foo")
}
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"
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 {
useString("foo")
}
}
func bce1() {
// tests overflow of max-min
a := int64(9223372036854774057)
b := int64(-1547)
z := int64(1337)
if a%z == b%z {
panic("invalid test: modulos should differ")
}
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$"
}
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$"
}
for i := int64(0); i < int64(len(a))+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
}
j := int64(len(a)) - 123
for i := int64(0); i < j+123+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
useString(a[i:]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$"
}
for i := int64(0); i < j+122+int64(-1<<63); i++ { // ERROR "Induction variable: limits \[0,\?\), increment 1$"
// len(a)-123+122+MinInt overflows when len(a) == 0, so a bound check is needed here
useString(a[i:])
}
}
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: limits \[-9223372036854775808,9223372036854775807\), increment 1$"
a[i] = i
}
return a
}
func issue26116a(a []int) {
// There is no induction variable here. The comparison is in the wrong direction.
for i := 3; i > 6; i++ {
a[i] = 0
}
for i := 7; i < 3; i-- {
a[i] = 1
}
}
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"
}
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"
}
return s
}
//go:noinline
func useString(a string) {
}
//go:noinline
func useSlice(a []int) {
}
func main() {
}
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