Teach BasicAliasAnalysis to understand constant gep indices that fall
beyond their associated static array type.
I believe that this fixes a legitimate bug, because BasicAliasAnalysis
already has code to check for this condition that works for non-constant
indices, however it was missing the case of constant indices. With this
change, it checks for both.
This fixes PR4267, and miscompiles of SPEC 188.ammp and 464.h264.href.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72451 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index d958746..d062045 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -611,18 +611,39 @@
if (G1OC != G2OC) {
// Handle the "be careful" case above: if this is an array/vector
// subscript, scan for a subsequent variable array index.
- if (isa<SequentialType>(BasePtr1Ty)) {
- const Type *NextTy =
- cast<SequentialType>(BasePtr1Ty)->getElementType();
+ if (const SequentialType *STy =
+ dyn_cast<SequentialType>(BasePtr1Ty)) {
+ const Type *NextTy = STy;
bool isBadCase = false;
- for (unsigned Idx = FirstConstantOper+1;
+ for (unsigned Idx = FirstConstantOper;
Idx != MinOperands && isa<SequentialType>(NextTy); ++Idx) {
const Value *V1 = GEP1Ops[Idx], *V2 = GEP2Ops[Idx];
if (!isa<Constant>(V1) || !isa<Constant>(V2)) {
isBadCase = true;
break;
}
+ // If the array is indexed beyond the bounds of the static type
+ // at this level, it will also fall into the "be careful" case.
+ // It would theoretically be possible to analyze these cases,
+ // but for now just be conservatively correct.
+ if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
+ if (cast<ConstantInt>(G1OC)->getZExtValue() >=
+ ATy->getNumElements() ||
+ cast<ConstantInt>(G2OC)->getZExtValue() >=
+ ATy->getNumElements()) {
+ isBadCase = true;
+ break;
+ }
+ if (const VectorType *VTy = dyn_cast<VectorType>(STy))
+ if (cast<ConstantInt>(G1OC)->getZExtValue() >=
+ VTy->getNumElements() ||
+ cast<ConstantInt>(G2OC)->getZExtValue() >=
+ VTy->getNumElements()) {
+ isBadCase = true;
+ break;
+ }
+ STy = cast<SequentialType>(NextTy);
NextTy = cast<SequentialType>(NextTy)->getElementType();
}