diff options
Diffstat (limited to 'llvm/lib/Analysis/ScalarEvolution.cpp')
| -rw-r--r-- | llvm/lib/Analysis/ScalarEvolution.cpp | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 072996d08f4..d49135a1b49 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -1778,6 +1778,32 @@ ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) { Ops.push_back(getZeroExtendExpr(Op, Ty, Depth + 1)); return getMulExpr(Ops, SCEV::FlagNUW, Depth + 1); } + + // zext(2^K * (trunc X to iN)) to iM -> + // 2^K * (zext(trunc X to i{N-K}) to iM)<nuw> + // + // Proof: + // + // zext(2^K * (trunc X to iN)) to iM + // = zext((trunc X to iN) << K) to iM + // = zext((trunc X to i{N-K}) << K)<nuw> to iM + // (because shl removes the top K bits) + // = zext((2^K * (trunc X to i{N-K}))<nuw>) to iM + // = (2^K * (zext(trunc X to i{N-K}) to iM))<nuw>. + // + if (SA->getNumOperands() == 2) + if (auto *MulLHS = dyn_cast<SCEVConstant>(SA->getOperand(0))) + if (MulLHS->getAPInt().isPowerOf2()) + if (auto *TruncRHS = dyn_cast<SCEVTruncateExpr>(SA->getOperand(1))) { + int NewTruncBits = getTypeSizeInBits(TruncRHS->getType()) - + MulLHS->getAPInt().logBase2(); + Type *NewTruncTy = IntegerType::get(getContext(), NewTruncBits); + return getMulExpr( + getZeroExtendExpr(MulLHS, Ty), + getZeroExtendExpr( + getTruncateExpr(TruncRHS->getOperand(), NewTruncTy), Ty), + SCEV::FlagNUW, Depth + 1); + } } // The cast wasn't folded; create an explicit cast node. |
