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Group unsafe-math optimizations for fsub into one block. No functional change. 

llvm-svn: 216616
This commit is contained in:
Sanjay Patel 2014-08-27 20:57:52 +00:00
parent 715c98aeec
commit ae402a35a0
1 changed files with 17 additions and 14 deletions
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31
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -6773,29 +6773,32 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
// fold (fsub c1, c2) -> c1-c2
if (N0CFP && N1CFP)
return DAG.getNode(ISD::FSUB, SDLoc(N), VT, N0, N1);
// fold (fsub A, 0) -> A
if (Options->UnsafeFPMath && N1CFP && N1CFP->getValueAPF().isZero())
return N0;
// fold (fsub 0, B) -> -B
if (Options->UnsafeFPMath && N0CFP && N0CFP->getValueAPF().isZero()) {
if (isNegatibleForFree(N1, LegalOperations, TLI, Options))
return GetNegatedExpression(N1, DAG, LegalOperations);
if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
return DAG.getNode(ISD::FNEG, dl, VT, N1);
}
// fold (fsub A, (fneg B)) -> (fadd A, B)
if (isNegatibleForFree(N1, LegalOperations, TLI, Options))
return DAG.getNode(ISD::FADD, dl, VT, N0,
GetNegatedExpression(N1, DAG, LegalOperations));
// If 'unsafe math' is enabled, fold
// (fsub x, x) -> 0.0 &
// (fsub x, (fadd x, y)) -> (fneg y) &
// (fsub x, (fadd y, x)) -> (fneg y)
// If 'unsafe math' is enabled, fold lots of things.
if (Options->UnsafeFPMath) {
// (fsub A, 0) -> A
if (N1CFP && N1CFP->getValueAPF().isZero())
return N0;
// (fsub 0, B) -> -B
if (N0CFP && N0CFP->getValueAPF().isZero()) {
if (isNegatibleForFree(N1, LegalOperations, TLI, Options))
return GetNegatedExpression(N1, DAG, LegalOperations);
if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
return DAG.getNode(ISD::FNEG, dl, VT, N1);
}
// (fsub x, x) -> 0.0
if (N0 == N1)
return DAG.getConstantFP(0.0f, VT);
// (fsub x, (fadd x, y)) -> (fneg y)
// (fsub x, (fadd y, x)) -> (fneg y)
if (N1.getOpcode() == ISD::FADD) {
SDValue N10 = N1->getOperand(0);
SDValue N11 = N1->getOperand(1);