From 1275e28dede2fda98c46c1c85892f893af451d01 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Fri, 23 Jan 2009 19:10:37 +0000 Subject: Fold x-0 to x in unsafe-fp-math mode. This comes up in the testcase from PR3376, and in fact is sufficient to completely avoid the problem in that testcase. There's an underlying problem though; TLI.isOperationLegal considers Custom to be Legal, which might be ok in some cases, but that's what DAGCombiner is using in many places to test if something is legal when LegalOperations is true. When DAGCombiner is running after legalize, this isn't sufficient. I'll address this in a separate commit. llvm-svn: 62860 --- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) (limited to 'llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp') diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 29744862089..6d1fdd23407 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -2402,15 +2402,22 @@ SDValue SelectionDAG::getNode(unsigned Opcode, MVT VT, case ISD::FMUL: case ISD::FDIV: case ISD::FREM: - if (UnsafeFPMath && Opcode == ISD::FADD) { - // 0+x --> x - if (ConstantFPSDNode *CFP = dyn_cast(N1)) - if (CFP->getValueAPF().isZero()) - return N2; - // x+0 --> x - if (ConstantFPSDNode *CFP = dyn_cast(N2)) - if (CFP->getValueAPF().isZero()) - return N1; + if (UnsafeFPMath) { + if (Opcode == ISD::FADD) { + // 0+x --> x + if (ConstantFPSDNode *CFP = dyn_cast(N1)) + if (CFP->getValueAPF().isZero()) + return N2; + // x+0 --> x + if (ConstantFPSDNode *CFP = dyn_cast(N2)) + if (CFP->getValueAPF().isZero()) + return N1; + } else if (Opcode == ISD::FSUB) { + // x-0 --> x + if (ConstantFPSDNode *CFP = dyn_cast(N2)) + if (CFP->getValueAPF().isZero()) + return N1; + } } assert(N1.getValueType() == N2.getValueType() && N1.getValueType() == VT && "Binary operator types must match!"); -- cgit v1.2.3