diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index 4b29824082f..af65cb74083 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -668,7 +668,8 @@ Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, /// follow non-inbounds geps. This allows it to remain usable for icmp ult/etc. /// folding. static Constant *stripAndComputeConstantOffsets(const DataLayout *TD, - Value *&V) { + Value *&V, + bool AllowNonInbounds = false) { assert(V->getType()->getScalarType()->isPointerTy()); // Without DataLayout, just be conservative for now. Theoretically, more could @@ -685,7 +686,8 @@ static Constant *stripAndComputeConstantOffsets(const DataLayout *TD, Visited.insert(V); do { if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { - if (!GEP->isInBounds() || !GEP->accumulateConstantOffset(*TD, Offset)) + if ((!AllowNonInbounds && !GEP->isInBounds()) || + !GEP->accumulateConstantOffset(*TD, Offset)) break; V = GEP->getPointerOperand(); } else if (Operator::getOpcode(V) == Instruction::BitCast) { @@ -1837,6 +1839,17 @@ static Constant *computePointerICmp(const DataLayout *TD, return ConstantInt::get(GetCompareTy(LHS), !CmpInst::isTrueWhenEqual(Pred)); } + + // Even if an non-inbounds GEP occurs along the path we can still optimize + // equality comparisons concerning the result. We avoid walking the whole + // chain again by starting where the last calls to + // stripAndComputeConstantOffsets left off and accumulate the offsets. + Constant *LHSNoBound = stripAndComputeConstantOffsets(TD, LHS, true); + Constant *RHSNoBound = stripAndComputeConstantOffsets(TD, RHS, true); + if (LHS == RHS) + return ConstantExpr::getICmp(Pred, + ConstantExpr::getAdd(LHSOffset, LHSNoBound), + ConstantExpr::getAdd(RHSOffset, RHSNoBound)); } // Otherwise, fail. |
