diff options
| -rw-r--r-- | src/cmd/compile/internal/gc/ssa.go | 33 | ||||
| -rw-r--r-- | test/loopbce.go | 6 | ||||
| -rw-r--r-- | test/prove.go | 4 |
3 files changed, 13 insertions, 30 deletions
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go index 84b9207481..d6b2bd3137 100644 --- a/src/cmd/compile/internal/gc/ssa.go +++ b/src/cmd/compile/internal/gc/ssa.go @@ -4029,6 +4029,7 @@ func (s *state) nilCheck(ptr *ssa.Value) { } // boundsCheck generates bounds checking code. Checks if 0 <= idx < len, branches to exit if not. +// len must be known to be nonnegative. // Starts a new block on return. // idx is already converted to full int width. func (s *state) boundsCheck(idx, len *ssa.Value) { @@ -4041,34 +4042,14 @@ func (s *state) boundsCheck(idx, len *ssa.Value) { s.check(cmp, panicindex) } -func couldBeNegative(v *ssa.Value) bool { - switch v.Op { - case ssa.OpSliceLen, ssa.OpSliceCap, ssa.OpStringLen: - return false - case ssa.OpConst64: - return v.AuxInt < 0 - case ssa.OpConst32: - return int32(v.AuxInt) < 0 - } - return true -} - // sliceBoundsCheck generates slice bounds checking code. Checks if 0 <= idx <= len, branches to exit if not. +// len must be known to be nonnegative. // Starts a new block on return. // idx and len are already converted to full int width. func (s *state) sliceBoundsCheck(idx, len *ssa.Value) { if Debug['B'] != 0 { return } - if couldBeNegative(len) { - // OpIsSliceInBounds requires second arg not negative; if it's not obviously true, must check. - cmpop := ssa.OpGeq64 - if len.Type.Size() == 4 { - cmpop = ssa.OpGeq32 - } - cmp := s.newValue2(cmpop, types.Types[TBOOL], len, s.zeroVal(len.Type)) - s.check(cmp, panicslice) - } // bounds check cmp := s.newValue2(ssa.OpIsSliceInBounds, types.Types[TBOOL], idx, len) @@ -4332,13 +4313,15 @@ func (s *state) slice(t *types.Type, v, i, j, k *ssa.Value, bounded bool) (p, l, if !bounded { // Panic if slice indices are not in bounds. - s.sliceBoundsCheck(i, j) - if j != k { - s.sliceBoundsCheck(j, k) - } + // Make sure we check these in reverse order so that we're always + // comparing against a value known to be nonnegative. See issue 28797. if k != cap { s.sliceBoundsCheck(k, cap) } + if j != k { + s.sliceBoundsCheck(j, k) + } + s.sliceBoundsCheck(i, j) } // Generate the following code assuming that indexes are in bounds. diff --git a/test/loopbce.go b/test/loopbce.go index 81f2524e95..e0a6463c5e 100644 --- a/test/loopbce.go +++ b/test/loopbce.go @@ -63,7 +63,7 @@ func f5(a [10]int) int { func f6(a []int) { for i := range a { // ERROR "Induction variable: limits \[0,\?\), increment 1$" - b := a[0:i] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$" "(\([0-9]+\) )?Proved Geq64$" + b := a[0:i] // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$" f6(b) } } @@ -186,10 +186,10 @@ func k0(a [100]int) [100]int { 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]) // ERROR "(\([0-9]+\) )?Proved IsSliceInBounds$" + 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$" "(\([0-9]+\) )?Proved Geq64$" + 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$" diff --git a/test/prove.go b/test/prove.go index eb0fb2a15e..2db0a841e2 100644 --- a/test/prove.go +++ b/test/prove.go @@ -269,7 +269,7 @@ func f11b(a []int, i int) { func f11c(a []int, i int) { useSlice(a[:i]) - useSlice(a[:i]) // ERROR "Proved Geq64$" "Proved IsSliceInBounds$" + useSlice(a[:i]) // ERROR "Proved IsSliceInBounds$" } func f11d(a []int, i int) { @@ -469,7 +469,7 @@ func f17(b []int) { // using the derived relation between len and cap. // This depends on finding the contradiction, since we // don't query this condition directly. - useSlice(b[:i]) // ERROR "Proved Geq64$" "Proved IsSliceInBounds$" + useSlice(b[:i]) // ERROR "Proved IsSliceInBounds$" } } |