[PATCH] D32605: Recognize CTLZ builtin

[Evgeny Stupachenko via Phabricator via llvm-commits]

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

The patch targeted to recognize and replace with ctlz (make countable) loops like:

while(n) {

  n >>= 1;
  i++;
  body();

}
use(i);

Should be replaced with:
ii = type_bitwidth(n) - ctlz(n);
for(j = 0; j < ii; j++) {
 body();
}
use(ii + i)


Repository:
  rL LLVM

https://reviews.llvm.org/D32605

Files:
  lib/Transforms/Scalar/LoopIdiomRecognize.cpp
  test/Transforms/LoopIdiom/ctlz.ll

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