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Add a DAGCombine xform to fold away redundant float->double->float conversions around sqrt instructions.

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I am assured by people more knowledgeable than me that there are no rounding issues in eliminating this.

This fixed <rdar://problem/8197504>.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108639 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2010-07-18 08:47:54 +00:00
parent 12f35c52a5
commit 3ecdfafe3b
1 changed files with 13 additions and 0 deletions
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13
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -4926,6 +4926,19 @@ SDValue DAGCombiner::visitFP_ROUND(SDNode *N) {
return DAG.getNode(ISD::FCOPYSIGN, N->getDebugLoc(), VT,
Tmp, N0.getOperand(1));
}
// (f32 fp_round (f64 sqrt (f64 fp_extend (f32)))) -> (f32 sqrt)
EVT VT0 = N0.getValueType();
if (VT == MVT::f32 &&
N0.getOpcode() == ISD::FSQRT && VT0 == MVT::f64) {
SDValue N1 = N0.getOperand(0);
EVT VT1 = N1.getValueType();
if (N1.getOpcode() == ISD::FP_EXTEND && VT1 == MVT::f64 &&
N1.getOperand(0).getValueType() == MVT::f32) {
return DAG.getNode(ISD::FSQRT, N->getDebugLoc(), MVT::f32,
N1.getOperand(0), N->getOperand(1));
}
}
return SDValue();
}