diff options
Diffstat (limited to 'llvm/lib/Target')
| -rw-r--r-- | llvm/lib/Target/X86/X86ISelLowering.cpp | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp index b1b7f5d4586..bc06ab9dc06 100644 --- a/llvm/lib/Target/X86/X86ISelLowering.cpp +++ b/llvm/lib/Target/X86/X86ISelLowering.cpp @@ -24738,9 +24738,11 @@ static SDValue PerformMulCombine(SDNode *N, SelectionDAG &DAG, MulAmt1 = 3; MulAmt2 = MulAmt / 3; } + + SDLoc DL(N); + SDValue NewMul; if (MulAmt2 && (isPowerOf2_64(MulAmt2) || MulAmt2 == 3 || MulAmt2 == 5 || MulAmt2 == 9)){ - SDLoc DL(N); if (isPowerOf2_64(MulAmt2) && !(N->hasOneUse() && N->use_begin()->getOpcode() == ISD::ADD)) @@ -24749,7 +24751,6 @@ static SDValue PerformMulCombine(SDNode *N, SelectionDAG &DAG, // is an add. std::swap(MulAmt1, MulAmt2); - SDValue NewMul; if (isPowerOf2_64(MulAmt1)) NewMul = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0), DAG.getConstant(Log2_64(MulAmt1), DL, MVT::i8)); @@ -24763,10 +24764,31 @@ static SDValue PerformMulCombine(SDNode *N, SelectionDAG &DAG, else NewMul = DAG.getNode(X86ISD::MUL_IMM, DL, VT, NewMul, DAG.getConstant(MulAmt2, DL, VT)); + } + + if (!NewMul) { + assert(MulAmt != 0 && MulAmt != (VT == MVT::i64 ? UINT64_MAX : UINT32_MAX) + && "Both cases that could cause potential overflows should have " + "already been handled."); + if (isPowerOf2_64(MulAmt - 1)) + // (mul x, 2^N + 1) => (add (shl x, N), x) + NewMul = DAG.getNode(ISD::ADD, DL, VT, N->getOperand(0), + DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0), + DAG.getConstant(Log2_64(MulAmt - 1), DL, + MVT::i8))); + else if (isPowerOf2_64(MulAmt + 1)) + // (mul x, 2^N - 1) => (sub (shl x, N), x) + NewMul = DAG.getNode(ISD::SUB, DL, VT, DAG.getNode(ISD::SHL, DL, VT, + N->getOperand(0), + DAG.getConstant(Log2_64(MulAmt + 1), + DL, MVT::i8)), N->getOperand(0)); + } + + if (NewMul) // Do not add new nodes to DAG combiner worklist. DCI.CombineTo(N, NewMul, false); - } + return SDValue(); } |
