cmd/compile: propagate unsigned relations for Rsh if arguments are positive

Updates #76332

Change-Id: Ifaa4d12897138d88d56b9d4e530c53dcee70bd58
Reviewed-on: https://go-review.googlesource.com/c/go/+/721205
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Reviewed-by: Keith Randall <khr@google.com>

diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go
index 4ffab848ba968cd12037d8040b53bb17a7898660..f6175a3bd709755fe77d90de36391b8ba4732a9e 100644 (file)
--- a/src/cmd/compile/internal/ssa/prove.go
+++ b/src/cmd/compile/internal/ssa/prove.go
@@ -2474,9 +2474,18 @@ func addLocalFacts(ft *factsTable, b *Block) {
                        //ft.update(b, v, v.Args[0], unsigned, gt|eq)
                        //ft.update(b, v, v.Args[1], unsigned, gt|eq)
                case OpDiv64, OpDiv32, OpDiv16, OpDiv8:
-                       if ft.isNonNegative(v.Args[0]) && ft.isNonNegative(v.Args[1]) {
-                               ft.update(b, v, v.Args[0], unsigned, lt|eq)
+                       if !ft.isNonNegative(v.Args[1]) {
+                               break
                        }
+                       fallthrough
+               case OpRsh8x64, OpRsh8x32, OpRsh8x16, OpRsh8x8,
+                       OpRsh16x64, OpRsh16x32, OpRsh16x16, OpRsh16x8,
+                       OpRsh32x64, OpRsh32x32, OpRsh32x16, OpRsh32x8,
+                       OpRsh64x64, OpRsh64x32, OpRsh64x16, OpRsh64x8:
+                       if !ft.isNonNegative(v.Args[0]) {
+                               break
+                       }
+                       fallthrough
                case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u,
                        OpRsh8Ux64, OpRsh8Ux32, OpRsh8Ux16, OpRsh8Ux8,
                        OpRsh16Ux64, OpRsh16Ux32, OpRsh16Ux16, OpRsh16Ux8,
@@ -2491,12 +2500,17 @@ func addLocalFacts(ft *factsTable, b *Block) {
                                zl := ft.limits[z.ID]
                                var uminDivisor uint64
                                switch v.Op {
-                               case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u:
+                               case OpDiv64u, OpDiv32u, OpDiv16u, OpDiv8u,
+                                       OpDiv64, OpDiv32, OpDiv16, OpDiv8:
                                        uminDivisor = zl.umin
                                case OpRsh8Ux64, OpRsh8Ux32, OpRsh8Ux16, OpRsh8Ux8,
                                        OpRsh16Ux64, OpRsh16Ux32, OpRsh16Ux16, OpRsh16Ux8,
                                        OpRsh32Ux64, OpRsh32Ux32, OpRsh32Ux16, OpRsh32Ux8,
-                                       OpRsh64Ux64, OpRsh64Ux32, OpRsh64Ux16, OpRsh64Ux8:
+                                       OpRsh64Ux64, OpRsh64Ux32, OpRsh64Ux16, OpRsh64Ux8,
+                                       OpRsh8x64, OpRsh8x32, OpRsh8x16, OpRsh8x8,
+                                       OpRsh16x64, OpRsh16x32, OpRsh16x16, OpRsh16x8,
+                                       OpRsh32x64, OpRsh32x32, OpRsh32x16, OpRsh32x8,
+                                       OpRsh64x64, OpRsh64x32, OpRsh64x16, OpRsh64x8:
                                        uminDivisor = 1 << zl.umin
                                default:
                                        panic("unreachable")

diff --git a/test/prove.go b/test/prove.go
index 1f893938e3ec7abf595514f919458b9f47db0bd8..38181b5fa58cf816bd57f83757cdbe2e6dab22a4 100644 (file)
--- a/test/prove.go
+++ b/test/prove.go
@@ -253,9 +253,10 @@ func f9(a, b bool) int {
 
 func f10(a string) int {
        n := len(a)
+       b := a[:n>>1] // ERROR "Proved IsSliceInBounds$"
        // We optimize comparisons with small constant strings (see cmd/compile/internal/gc/walk.go),
        // so this string literal must be long.
-       if a[:n>>1] == "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" {
+       if b == "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" {
                return 0
        }
        return 1
@@ -1084,6 +1085,13 @@ func issue57077(s []int) (left, right []int) {
        return
 }
 
+func issue76332(s []int) (left, right []int) {
+       middle := len(s) >> 1
+       left = s[:middle]     // ERROR "Proved IsSliceInBounds$"
+       right = s[middle:]    // ERROR "Proved IsSliceInBounds$"
+       return
+}
+
 func issue51622(b []byte) int {
        if len(b) >= 3 && b[len(b)-3] == '#' { // ERROR "Proved IsInBounds$"
                return len(b)