[PATCH] D45448: [CVP] simplify phi with constant incoming values that match common variable edge values

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: sanjoy, jlebar, efriedma.
Herald added a subscriber: mcrosier.

This is based on an example that was recently posted on llvm-dev:

  void *propagate_null(void* b, int* g) {
          if (!b) {
                  return 0;
          }
          (*g)++;
          return b;
  }

https://godbolt.org/g/xYk3qG

The original code or constant propagation in other passes has obscured the fact that the phi can be removed completely.

There's an instcombine proposal to fix part of this at https://reviews.llvm.org/D45378, but I don't think we want instcombine doing things like that (and I'm not sure that patch is correct as-is).


https://reviews.llvm.org/D45448

Files:
  lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
  test/Transforms/CorrelatedValuePropagation/phi-common-val.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D45448.141690.patch
Type: text/x-patch
Size: 5963 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180409/e6b3ebca/attachment-0001.bin>