[PATCH] D74165: [x86] [DAGCombine] Prefer shifts of constant widths.

[Justin Lebar via Phabricator via llvm-commits]

jlebar added a comment.

@RKSimon and others, thank you for the review and comments.  Sorry for my delay here; this has changed from being my day job to my weekend hobby, and that made a bigger difference in my responsiveness than I'd like or than I expected.

I believe I've addressed all of the comments.  I haven't pushed the tests sans this change just on the principle that I don't want to add tests that might end up being useless (if this patch doesn't land for some reason), but I've rebased this patch atop a commit which adds those tests.  So when I commit this it will be as two patches, one to add the tests as-is, and then another to update the test with this patch.



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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:7446
+  if (SDValue V = visitShiftOrRotate(N))
+    return V;
+
----------------
RKSimon wrote:
> Move these lower down to after SimplifyDemandedBits, we tend to have the constant folding / cleanup combines first.
Done.  This also allowed me to remove the `Level >= AfterLegalizeTypes`, which I never liked.


Repository:
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https://reviews.llvm.org/D74165