[SLSR] handles off bounds GEPs
Summary:
The old requirement on GEP candidates being in bounds is unnecessary.
For off-bound GEPs, we still have
&B[i * S] = B + (i * S) * e = B + (i * e) * S
Test Plan: slsr_offbound_gep in slsr-gep.ll
Reviewers: meheff
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8809
llvm-svn: 233949
diff --git a/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
index e71031c..940ab58 100644
--- a/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
@@ -333,7 +333,8 @@
void StraightLineStrengthReduce::allocateCandidateAndFindBasisForGEP(
const SCEV *B, ConstantInt *Idx, Value *S, uint64_t ElementSize,
Instruction *I) {
- // I = B + sext(Idx *nsw S) *nsw ElementSize
+ // I = B + sext(Idx *nsw S) * ElementSize
+ // = B + (sext(Idx) * sext(S)) * ElementSize
// = B + (sext(Idx) * ElementSize) * sext(S)
// Casting to IntegerType is safe because we skipped vector GEPs.
IntegerType *IntPtrTy = cast<IntegerType>(DL->getIntPtrType(I->getType()));
@@ -367,7 +368,7 @@
// sext'ed multiplication.
if (match(ArrayIdx, m_NSWMul(m_Value(LHS), m_ConstantInt(RHS)))) {
// SLSR is currently unsafe if i * S may overflow.
- // GEP = Base + sext(LHS *nsw RHS) *nsw ElementSize
+ // GEP = Base + sext(LHS *nsw RHS) * ElementSize
allocateCandidateAndFindBasisForGEP(Base, RHS, LHS, ElementSize, GEP);
}
}
@@ -472,19 +473,25 @@
case Candidate::GEP:
{
Type *IntPtrTy = DL->getIntPtrType(C.Ins->getType());
+ bool InBounds = cast<GetElementPtrInst>(C.Ins)->isInBounds();
if (BumpWithUglyGEP) {
// C = (char *)Basis + Bump
unsigned AS = Basis.Ins->getType()->getPointerAddressSpace();
Type *CharTy = Type::getInt8PtrTy(Basis.Ins->getContext(), AS);
Reduced = Builder.CreateBitCast(Basis.Ins, CharTy);
- // We only considered inbounds GEP as candidates.
- Reduced = Builder.CreateInBoundsGEP(Reduced, Bump);
+ if (InBounds)
+ Reduced = Builder.CreateInBoundsGEP(Reduced, Bump);
+ else
+ Reduced = Builder.CreateGEP(Reduced, Bump);
Reduced = Builder.CreateBitCast(Reduced, C.Ins->getType());
} else {
// C = gep Basis, Bump
// Canonicalize bump to pointer size.
Bump = Builder.CreateSExtOrTrunc(Bump, IntPtrTy);
- Reduced = Builder.CreateInBoundsGEP(Basis.Ins, Bump);
+ if (InBounds)
+ Reduced = Builder.CreateInBoundsGEP(Basis.Ins, Bump);
+ else
+ Reduced = Builder.CreateGEP(Basis.Ins, Bump);
}
}
break;