optimize vector fneg of bitcasted integer value
This patch allows a vector fneg of a bitcasted integer value to be optimized in the same way that we already optimize a scalar fneg. If the integer variable is a constant, we can precompute the result and not require any logic ops.
This patch is very similar to a fabs patch committed at r214892.
Differential Revision: http://reviews.llvm.org/D4852
llvm-svn: 215646
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4f898bc..c1ff817 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7321,22 +7321,27 @@
&DAG.getTarget().Options))
return GetNegatedExpression(N0, DAG, LegalOperations);
- // Transform fneg(bitconvert(x)) -> bitconvert(x^sign) to avoid loading
+ // Transform fneg(bitconvert(x)) -> bitconvert(x ^ sign) to avoid loading
// constant pool values.
- // TODO: We can also optimize for vectors here, but we need to make sure
- // that the sign mask is created properly for each vector element.
if (!TLI.isFNegFree(VT) && N0.getOpcode() == ISD::BITCAST &&
- !VT.isVector() &&
- N0.getNode()->hasOneUse() &&
- N0.getOperand(0).getValueType().isInteger()) {
+ N0.getNode()->hasOneUse()) {
SDValue Int = N0.getOperand(0);
EVT IntVT = Int.getValueType();
if (IntVT.isInteger() && !IntVT.isVector()) {
+ APInt SignMask;
+ if (N0.getValueType().isVector()) {
+ // For a vector, get a mask such as 0x80... per scalar element
+ // and splat it.
+ SignMask = APInt::getSignBit(N0.getValueType().getScalarSizeInBits());
+ SignMask = APInt::getSplat(IntVT.getSizeInBits(), SignMask);
+ } else {
+ // For a scalar, just generate 0x80...
+ SignMask = APInt::getSignBit(IntVT.getSizeInBits());
+ }
Int = DAG.getNode(ISD::XOR, SDLoc(N0), IntVT, Int,
- DAG.getConstant(APInt::getSignBit(IntVT.getSizeInBits()), IntVT));
+ DAG.getConstant(SignMask, IntVT));
AddToWorklist(Int.getNode());
- return DAG.getNode(ISD::BITCAST, SDLoc(N),
- VT, Int);
+ return DAG.getNode(ISD::BITCAST, SDLoc(N), VT, Int);
}
}