The patch exclude a case from zero check skip in

 CTLZ idiom recognition (r303102).

Summary:

The following case:
i = 1;
if(n)
  while (n >>= 1)
    i++;
use(i);

Was converted to:

i = 1;
if(n)
  i += builtin_ctlz(n >> 1, false);
use(i);

Which is not correct. The patch make it:

i = 1;
if(n)
  i += builtin_ctlz(n >> 1, true);
use(i);

From: Evgeny Stupachenko <evstupac@gmail.com>
llvm-svn: 303212