[PATCH] D33137: [DAGCombiner] use narrow vector ops to eliminate concat/extract (PR32790)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14476
+  SDValue BinOp = Extract->getOperand(0);
+  if (BinOp.getOpcode() == ISD::BITCAST)
+    BinOp = BinOp.getOperand(0);
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spatel wrote:
> RKSimon wrote:
> > I'm starting to think that X86ISelLowering's peekThroughBitcasts and peekThroughOneUseBitcasts helpers should be exposed globally.
> Probably a good idea. Although we always fold a bitcast-of-a-bitcast, right? I've never seen a need for those to loop.
Interestingly, there are a load of codegen regressions if you tweak them to just peek through the first bitcast.....


https://reviews.llvm.org/D33137