- Fix a x86 vector isel bug: illegal transformation of a vector_shuffle into a
shift.
- Add a readme entry for a missing vector_shuffle optimization that results in
awful codegen.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52740 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index fdff418..f1c2ecf 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1859,12 +1859,16 @@
/// getShuffleScalarElt - Returns the scalar element that will make up the ith
/// element of the result of the vector shuffle.
-SDOperand SelectionDAG::getShuffleScalarElt(const SDNode *N, unsigned Idx) {
+SDOperand SelectionDAG::getShuffleScalarElt(const SDNode *N, unsigned i) {
MVT VT = N->getValueType(0);
SDOperand PermMask = N->getOperand(2);
+ SDOperand Idx = PermMask.getOperand(i);
+ if (Idx.getOpcode() == ISD::UNDEF)
+ return getNode(ISD::UNDEF, VT.getVectorElementType());
+ unsigned Index = cast<ConstantSDNode>(Idx)->getValue();
unsigned NumElems = PermMask.getNumOperands();
- SDOperand V = (Idx < NumElems) ? N->getOperand(0) : N->getOperand(1);
- Idx %= NumElems;
+ SDOperand V = (Index < NumElems) ? N->getOperand(0) : N->getOperand(1);
+ Index %= NumElems;
if (V.getOpcode() == ISD::BIT_CONVERT) {
V = V.getOperand(0);
@@ -1872,16 +1876,12 @@
return SDOperand();
}
if (V.getOpcode() == ISD::SCALAR_TO_VECTOR)
- return (Idx == 0) ? V.getOperand(0)
+ return (Index == 0) ? V.getOperand(0)
: getNode(ISD::UNDEF, VT.getVectorElementType());
if (V.getOpcode() == ISD::BUILD_VECTOR)
- return V.getOperand(Idx);
- if (V.getOpcode() == ISD::VECTOR_SHUFFLE) {
- SDOperand Elt = PermMask.getOperand(Idx);
- if (Elt.getOpcode() == ISD::UNDEF)
- return getNode(ISD::UNDEF, VT.getVectorElementType());
- return getShuffleScalarElt(V.Val,cast<ConstantSDNode>(Elt)->getValue());
- }
+ return V.getOperand(Index);
+ if (V.getOpcode() == ISD::VECTOR_SHUFFLE)
+ return getShuffleScalarElt(V.Val, Index);
return SDOperand();
}