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

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

Judging by the code in SystemZISelDAGToDAG.cpp that calls UpdateNodeOperands during select, I don't think it works the way I thought. The SystemZ code calls ReplaceNode if UpdateNodeOperands does CSE. I tried to change that to just assign over Node. Which would make it similar to what I'm trying to do here. But it ended up leaving a node unselected.


Repository:
  rL LLVM

https://reviews.llvm.org/D48789