[PATCH] D59024: [CGP] Limit distance between overflow math and cmp

[Sam Parker via Phabricator via llvm-commits]

samparker created this revision.
samparker added reviewers: spatel, RKSimon, dmgreen.
Herald added a subscriber: javed.absar.

Inserting an overflowing arithmetic intrinsic can increase register pressure by producing two values at a point where only one is needed, while the second use maybe several blocks away. This increase in pressure could be more detrimental on performance than rematerialising one of the original instructions.

      

So, I've added a check that calculates the distance (in basic blocks) between the cmp and math instructions, limiting this to two. This covers the existing test cases.


https://reviews.llvm.org/D59024

Files:
  lib/CodeGen/CodeGenPrepare.cpp
  test/Transforms/CodeGenPrepare/ARM/overflow-intrinsics.ll

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