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Be careful when looking through a vbit_convert. Optimizing this:

Browse Source 
(vector_shuffle
  (vbitconvert (vbuildvector (copyfromreg v4f32), 1, v4f32), 4, f32),
  (undef, undef, undef, undef), (0, 0, 0, 0), 4, f32)
to the
  vbitconvert
is a very bad idea.

llvm-svn: 30989
This commit is contained in:
Evan Cheng 2006-10-16 22:49:37 +00:00
parent a156538e34
commit 2d9318cff1
1 changed files with 11 additions and 2 deletions
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13
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -3108,8 +3108,17 @@ SDOperand DAGCombiner::visitVVECTOR_SHUFFLE(SDNode *N) {
// all scalar elements the same.
if (isSplat) {
SDNode *V = N0.Val;
if (V->getOpcode() == ISD::VBIT_CONVERT)
V = V->getOperand(0).Val;
// If this is a vbit convert that changes the element type of the vector but
// not the number of vector elements, look through it. Be careful not to
// look though conversions that change things like v4f32 to v2f64.
if (V->getOpcode() == ISD::VBIT_CONVERT) {
SDOperand ConvInput = V->getOperand(0);
if (NumElts ==
ConvInput.getConstantOperandVal(ConvInput.getNumOperands()-2))
V = ConvInput.Val;
}
if (V->getOpcode() == ISD::VBUILD_VECTOR) {
unsigned NumElems = V->getNumOperands()-2;
if (NumElems > BaseIdx) {