[Bug tree-optimization/125442] Missed (x == 0) | ((x | y) == 0) to (x == 0)

[souradiptodas6 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125442

Souradipto Das <souradiptodas6 at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |souradiptodas6 at gmail dot com

--- Comment #3 from Souradipto Das <souradiptodas6 at gmail dot com> ---
Created attachment 64563
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64563&action=edit
Fix missed optimization via match.pd pattern and add live verification testcase

I've attached a patch containing a match.pd simplification rule that resolves
this missed optimization.

The rule successfully catches and collapses the redundant bitwise chain down to
the expected single comparison. Tested locally on x86_64-pc-linux-gnu via `make
check-gcc` using the literal testcase provided in the description, yielding 3
expected passes with zero regressions.

### Verified Optimized GIMPLE Output:
_Bool src (long unsigned int x, long unsigned int y)
{
  _Bool _10;

  <bb 2>:
  _10_3 = x_1(D) == 0;
  return _10_3;
}