[Bug tree-optimization/126977] New: [17 Regression] factor_out_conditional_operation breaks __builtin_crc* handling

"pinskia at gcc dot gnu.org via Gcc-bugs" <[email protected]> Fri, 21 Aug 2026 07:38:28 +0000

Newsgroups	gmane.comp.gcc.bugs
Message-ID	<[email protected]/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126977

            Bug ID: 126977
           Summary: [17 Regression] factor_out_conditional_operation
                    breaks __builtin_crc* handling
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Created attachment 65381
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65381&action=edit
testcase

The attached testcase should compile but on the trunk we get:
<source>: In function 'crc32_data32':
<source>:2:5: error: third argument to 'crc' builtins must be a constant
    2 | int crc32_data32 (unsigned x, unsigned y, int z)
      |     ^~~~~~~~~~~~

This is because for the 3rd operand of the __builtin_crc* __builtin_rev_crc*
builtins is special and need to be a constant.

Noticed while reviewing
https://gcc.gnu.org/pipermail/gcc-patches/2026-August/728405.html .