[PATCH] D39536: [PowerPC] Eliminate redundant register copys after register allocation

[Hiroshi Inoue via Phabricator via llvm-commits]

inouehrs added a comment.

In https://reviews.llvm.org/D39536#926354, @MatzeB wrote:

> Is this like the existing MachineCopyPropagation pass but working accross multiple blocks? Would https://reviews.llvm.org/D30751 solve your problem as well?


The two optimization are mostly disjoint.
Copy source forwarding optimizes

  mr 3, 4
  addi 5, 3, 1 

to

  mr 3, 4
  addi 5, 4, 1 

but this optimization intends to rewrite

  addi 4, 3, 1 
  mr 3, 4

to

  addi 3, 3, 1 

or eliminate

  mr 4, 3
  mr 3, 4


https://reviews.llvm.org/D39536