diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/LegalizeDAG.cpp | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp index a511202a53..08e8d776fd 100644 --- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp +++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp @@ -1156,15 +1156,25 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) { break; } case ISD::CTTZ: { - // for now, we use: { return popcount(~x & (x - 1)); } - // but see also http://www.hackersdelight.org/HDcode/ntz.cc + // for now, we use: { return popcount(~x & (x - 1)); } + // unless the target has ctlz but not ctpop, in which case we use: + // { return 32 - nlz(~x & (x-1)); } + // see also http://www.hackersdelight.org/HDcode/ntz.cc MVT::ValueType VT = Tmp1.getValueType(); Tmp2 = DAG.getConstant(~0ULL, VT); Tmp3 = DAG.getNode(ISD::AND, VT, DAG.getNode(ISD::XOR, VT, Tmp1, Tmp2), DAG.getNode(ISD::SUB, VT, Tmp1, DAG.getConstant(1, VT))); - Result = LegalizeOp(DAG.getNode(ISD::CTPOP, VT, Tmp3)); + // If ISD::CTLZ is legal and CTPOP isn't, then do that instead + if (TLI.getOperationAction(ISD::CTPOP, VT) != TargetLowering::Legal && + TLI.getOperationAction(ISD::CTLZ, VT) == TargetLowering::Legal) { + Result = LegalizeOp(DAG.getNode(ISD::SUB, VT, + DAG.getConstant(getSizeInBits(VT), VT), + DAG.getNode(ISD::CTLZ, VT, Tmp3))); + } else { + Result = LegalizeOp(DAG.getNode(ISD::CTPOP, VT, Tmp3)); + } break; } default: |