diff options
| -rw-r--r-- | llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp index 6693a26e889..cb6223b070a 100644 --- a/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp +++ b/llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp @@ -1292,13 +1292,15 @@ bool LoopIdiomRecognize::recognizeAndInsertCTLZ() { BasicBlock *PH = CurLoop->getLoopPreheader(); Value *InitX = PhiX->getIncomingValueForBlock(PH); // If we check X != 0 before entering the loop we don't need a zero - // check in CTLZ intrinsic. - if (BasicBlock *PreCondBB = PH->getSinglePredecessor()) - if (BranchInst *PreCondBr = - dyn_cast<BranchInst>(PreCondBB->getTerminator())) { - if (matchCondition(PreCondBr, PH) == InitX) - ZeroCheck = true; - } + // check in CTLZ intrinsic, but only if Cnt Phi is not used outside of the + // loop (if it is used we count CTLZ(X >> 1)). + if (!IsCntPhiUsedOutsideLoop) + if (BasicBlock *PreCondBB = PH->getSinglePredecessor()) + if (BranchInst *PreCondBr = + dyn_cast<BranchInst>(PreCondBB->getTerminator())) { + if (matchCondition(PreCondBr, PH) == InitX) + ZeroCheck = true; + } // Check if CTLZ intrinsic is profitable. Assume it is always profitable // if we delete the loop (the loop has only 6 instructions): |
