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Add a xform to the DAG combiner. 

Transform:

        (fsub x, (fadd x, y)) -> (fneg y) and
        (fsub x, (fadd y, x)) -> (fneg y)

if 'unsafe math' is specified.
<rdar://problem/7540295>

llvm-svn: 152777
This commit is contained in:
Bill Wendling 2012-03-15 05:12:00 +00:00
parent aeef2ae8f9
commit df170db2f6
1 changed files with 17 additions and 0 deletions
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17
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -5568,6 +5568,23 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0,
GetNegatedExpression(N1, DAG, LegalOperations));
// If 'unsafe math' is enabled, fold
// (fsub x, (fadd x, y)) -> (fneg y) &
// (fsub x, (fadd y, x)) -> (fneg y)
if (DAG.getTarget().Options.UnsafeFPMath) {
if (N1.getOpcode() == ISD::FADD) {
SDValue N10 = N1->getOperand(0);
SDValue N11 = N1->getOperand(1);
if (N10 == N0 && isNegatibleForFree(N11, LegalOperations, TLI,
&DAG.getTarget().Options))
return GetNegatedExpression(N11, DAG, LegalOperations);
else if (N11 == N0 && isNegatibleForFree(N10, LegalOperations, TLI,
&DAG.getTarget().Options))
return GetNegatedExpression(N10, DAG, LegalOperations);
}
}
return SDValue();
}