[PATCH] D34117: PR32632 Add a case to remove loop compare

[Evgeny Stupachenko via Phabricator via llvm-commits]

evstupac created this revision.
Herald added a subscriber: mzolotukhin.

The patch add a case to eliminate comparisons like:

  for (i = 84; i > 1; i--)
   for (j = i; j < i; j++)

which exit at first loop iteration.

Build and lit tests are passed.
No significant performance changes.
spec2000 - build same all
spec2006 - build same all, but 400 and 433 (with less than 1% gain).


Repository:
  rL LLVM

https://reviews.llvm.org/D34117

Files:
  include/llvm/Analysis/ScalarEvolution.h
  lib/Analysis/ScalarEvolution.cpp
  test/Transforms/IndVarSimplify/first_iter_exit.ll

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