[Bug middle-end/123826] New: folding of `pow(a, 2.0)` into a*a causes errno not to be set

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123826

            Bug ID: 123826
           Summary: folding of `pow(a, 2.0)` into a*a causes errno not to
                    be set
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Created attachment 63490
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=63490&action=edit
testcase

From:
https://mastodon.social/@dotstdy/115960430921170421
https://godbolt.org/z/xahMha3zY

Take the attached testcase.
GCC will  simplify `pow(a, 2.0)` at -O2 into a*a and constant fold
`pow(DBL_MAX, 2.0)` (in general). This means we lose the errno setting.

Note changing this might lose some performance ...