[x86] Fix PR22377, a regression with the new vector shuffle legality
test.
This was just a matter of the DAG combine for vector shuffles being too
aggressive. This is a bit of a grey area, but I think generally if we
can re-use intermediate shuffles, we should. Certainly, given the test
cases I have available, this seems like the right call.
llvm-svn: 229285
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 747aa43..8571091 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -11770,8 +11770,9 @@
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(A, C, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(B, C, M2)
// Don't try to fold shuffles with illegal type.
- if (N0.getOpcode() == ISD::VECTOR_SHUFFLE && Level < AfterLegalizeDAG &&
- TLI.isTypeLegal(VT)) {
+ // Only fold if this shuffle is the only user of the other shuffle.
+ if (N0.getOpcode() == ISD::VECTOR_SHUFFLE && N->isOnlyUserOf(N0.getNode()) &&
+ Level < AfterLegalizeDAG && TLI.isTypeLegal(VT)) {
ShuffleVectorSDNode *OtherSV = cast<ShuffleVectorSDNode>(N0);
// The incoming shuffle must be of the same type as the result of the