diff options
Diffstat (limited to 'lib/Target/SystemZ')
| -rw-r--r-- | lib/Target/SystemZ/SystemZISelLowering.cpp | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp index 6c443b59f7..baef2c1d0b 100644 --- a/lib/Target/SystemZ/SystemZISelLowering.cpp +++ b/lib/Target/SystemZ/SystemZISelLowering.cpp @@ -1271,6 +1271,26 @@ static unsigned reverseCCMask(unsigned CCMask) { (CCMask & SystemZ::CCMASK_CMP_UO)); } +// Check whether C tests for equality between X and Y and whether X - Y +// or Y - X is also computed. In that case it's better to compare the +// result of the subtraction against zero. +static void adjustForSubtraction(SelectionDAG &DAG, Comparison &C) { + if (C.CCMask == SystemZ::CCMASK_CMP_EQ || + C.CCMask == SystemZ::CCMASK_CMP_NE) { + for (SDNode::use_iterator I = C.Op0->use_begin(), E = C.Op0->use_end(); + I != E; ++I) { + SDNode *N = *I; + if (N->getOpcode() == ISD::SUB && + ((N->getOperand(0) == C.Op0 && N->getOperand(1) == C.Op1) || + (N->getOperand(0) == C.Op1 && N->getOperand(1) == C.Op0))) { + C.Op0 = SDValue(N, 0); + C.Op1 = DAG.getConstant(0, N->getValueType(0)); + return; + } + } + } +} + // Check whether C compares a floating-point value with zero and if that // floating-point value is also negated. In this case we can use the // negation to set CC, so avoiding separate LOAD AND TEST and @@ -1540,6 +1560,7 @@ static Comparison getCmp(SelectionDAG &DAG, SDValue CmpOp0, SDValue CmpOp1, C.CCMask &= ~SystemZ::CCMASK_CMP_UO; adjustZeroCmp(DAG, C); adjustSubwordCmp(DAG, C); + adjustForSubtraction(DAG, C); } if (shouldSwapCmpOperands(C)) { |