[PATCH] D48789: [X86] Replace (32/64 - n) shift amounts with (neg n) since the shift amount is masked in hardware

[Nirav Dave via Phabricator via llvm-commits]

niravd added a comment.

> I’m pretty sure the case where UpdateNodeOperands returns an existing node instead of updating N doesn’t work. But I haven’t been able to trigger it with a test.

Ah, I think you're right; if we find an existing node, other references to the old node will not be updated. But calling ReplaceNode in that case should be sufficient. 
If it's too hard to get a test case, I'm in favor of commit this without a test case.


Repository:
  rL LLVM

https://reviews.llvm.org/D48789