[PATCH] D20531: MachineCopyPropagation: remove some more copys when they are not needed

[Quentin Colombet via llvm-commits]

qcolombet added a comment.

Hi Jonas,

> What are the exact checks that need to be done?


That’s the thing, you can’t really know at this stage.
An approximation would be to do this transformation for explicit uses only. But I would rather stay out of that game to be safe.

Right now, this pass is about removing no-op copies. It does not try to do recoloring, which is what your patch aim for.

If we want to go for recoloring, we need to handle that before the virtual registers are rewritten, because at this point, we can assume that all present physical registers are ABI constraints.

Cheers,
-Quentin


http://reviews.llvm.org/D20531