[Bug tree-optimization/126694] New: Fold a magnitude comparison against zero

"ktkachov at gcc dot gnu.org via Gcc-bugs" <[email protected]> Thu, 06 Aug 2026 14:01:02 +0000

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126694

            Bug ID: 126694
           Summary: Fold a magnitude comparison against zero
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: easyhack, missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---

int f (double x) { return __builtin_fabs (x) <= 0.0; }

We could generated for aarch64 -fno-trapping-math:
        fcmp    d0, #0.0
        cset    w0, eq

instead of the current:

        fabs    d0, d0
        fcmpe   d0, #0.0
        cset    w0, ls