diff options
Diffstat (limited to 'llvm/lib/Analysis/Loads.cpp')
| -rw-r--r-- | llvm/lib/Analysis/Loads.cpp | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp index 255a7ae..4f0b92f5 100644 --- a/llvm/lib/Analysis/Loads.cpp +++ b/llvm/lib/Analysis/Loads.cpp @@ -313,6 +313,13 @@ bool llvm::isDereferenceableAndAlignedInLoop(LoadInst *LI, Loop *L, const auto *Offset = dyn_cast<SCEVConstant>(StartS->getOperand(0)); const auto *NewBase = dyn_cast<SCEVUnknown>(StartS->getOperand(1)); if (StartS->getNumOperands() == 2 && Offset && NewBase) { + // The following code below assumes the offset is unsigned, but GEP + // offsets are treated as signed so we can end up with a signed value + // here too. For example, suppose the initial PHI value is (i8 255), + // the offset will be treated as (i8 -1) and sign-extended to (i64 -1). + if (Offset->getAPInt().isNegative()) + return false; + // For the moment, restrict ourselves to the case where the offset is a // multiple of the requested alignment and the base is aligned. // TODO: generalize if a case found which warrants |