Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.723 -> 1.724 --- Log message: Fix PR1253: http://llvm.org/PR1253 and xor2.ll:test[01] --- Diffs of the changes: (+30 -1) InstructionCombining.cpp | 31 ++++++++++++++++++++++++++++++- 1 files changed, 30 insertions(+), 1 deletion(-) Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.723 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.724 --- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.723 Mon Apr 2 08:45:30 2007 +++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Mon Apr 2 20:47:41 2007 @@ -4714,7 +4714,36 @@ // instruction can be folded into the icmp if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) switch (LHSI->getOpcode()) { - case Instruction::And: + case Instruction::Xor: // (icmp pred (and X, XorCST), CI) + if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) { + // If this is a comparison that tests the signbit (X < 0) or (x > -1), + // fold the xor. + if (I.getPredicate() == ICmpInst::ICMP_SLT && CI->isZero() || + I.getPredicate() == ICmpInst::ICMP_SGT && CI->isAllOnesValue()) { + Value *CompareVal = LHSI->getOperand(0); + + // If the sign bit of the XorCST is not set, there is no change to + // the operation, just stop using the Xor. + if (!XorCST->getValue().isNegative()) { + I.setOperand(0, CompareVal); + AddToWorkList(LHSI); + return &I; + } + + // Was the old condition true if the operand is positive? + bool isTrueIfPositive = I.getPredicate() == ICmpInst::ICMP_SGT; + + // If so, the new one isn't. + isTrueIfPositive ^= true; + + if (isTrueIfPositive) + return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal, SubOne(CI)); + else + return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal, AddOne(CI)); + } + } + break; + case Instruction::And: // (icmp pred (and X, AndCST), CI) if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) && LHSI->getOperand(0)->hasOneUse()) { ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1)); _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
