diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 7e870e6c2f99..b82d1028b4f1 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -507,6 +507,28 @@ SDOperand SelectionDAG::getSetCC(ISD::CondCode Cond, MVT::ValueType VT, // FIXME: Implement the rest of these. + + // Fold bit comparisons when we can. + if ((Cond == ISD::SETEQ || Cond == ISD::SETNE) && + VT == N1.getValueType() && N1.getOpcode() == ISD::AND) + if (ConstantSDNode *AndRHS = + dyn_cast(N1.getOperand(1))) { + if (Cond == ISD::SETNE && C2 == 0) {// (X & 8) != 0 --> (X & 8) >> 3 + // Perform the xform if the AND RHS is a single bit. + if ((AndRHS->getValue() & (AndRHS->getValue()-1)) == 0) { + return getNode(ISD::SRL, VT, N1, + getConstant(ExactLog2(AndRHS->getValue()), + TLI.getShiftAmountTy())); + } + } else if (Cond == ISD::SETEQ && C2 == AndRHS->getValue()) { + // (X & 8) == 8 --> (X & 8) >> 3 + // Perform the xform if C2 is a single bit. + if ((C2 & (C2-1)) == 0) { + return getNode(ISD::SRL, VT, N1, + getConstant(ExactLog2(C2),TLI.getShiftAmountTy())); + } + } + } } } else if (isa(N1.Val)) { // Ensure that the constant occurs on the RHS.