[PATCH] D154953: [InstSimplify] Remove the remainder loop if we know the mask is always true

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo added a comment.

This commit caused misoptimizations in the WMA decoder in ffmpeg, observed on all architectures. The misoptimization can be observed with https://martin.st/temp/wma-preproc.c, compiled with `clang -target aarch64-linux-gnu -c -O3 wma-preproc.c -o libavcodec/wma.o`.

For a full runtime reproducible case:

  $ git clone git://source.ffmpeg.org/ffmpeg
  $ mkdir ffmpeg-build
  $ cd ffmpeg-build
  $ ../ffmpeg/configure --cc=clang --samples=../fate-samples
  $ make -j$(nproc)
  $ make fate-rsync
  $ make fate-wmapro-2ch

If it takes a long time to fix, I'd appreciate reverting it in the meantime.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D154953/new/

https://reviews.llvm.org/D154953