[Bug tree-optimization/113741] New: missed / wrong optimization switch transformation to same function call

[Bug tree-optimization/113741] New: missed / wrong optimization switch transformation to same function call

[b.buschinski at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113741

            Bug ID: 113741
           Summary: missed / wrong optimization switch transformation to
                    same function call
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: b.buschinski at googlemail dot com
  Target Milestone: ---

Created attachment 57308
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57308&action=edit
Attached code + asm from the compiler explorer link

Compiler Explorer Link: https://godbolt.org/z/KozK9M5YY

The code is reduced from a "hot" path with huge macros.

I actually improved the macros with adding the "else" in the code, but I
noticed it suddenly created even more instructions and got slower.

The GCC version has 52 ASM lines.
The clang version only 9 ASM lines.

Clang is doing a better job here.

As far as I understand the ASM code, GCC generates a switch statement, but
after the:

cmp     edi, 5
ja      .L11

it should not be needed at all anymore.

Additionally, GCC "reloads" the static values again

(for every .L*: label)
mov     edi, 4

, which are already stored in "i" (C code).

Tested with GCC-13.2 and compiler explorer gcc "trunk".
On x86_64 Linux.


Please let me know if you need any additional details or if this report was
useful at all.

[Bug tree-optimization/113741] missed / wrong optimization switch transformation to same function call

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113741

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sjames at gcc dot gnu.org

--- Comment #1 from Sam James <sjames at gcc dot gnu.org> ---
Note that we reserve the term "wrong" for invalid results or otherwise unsound
transformations.

[Bug tree-optimization/113741] missed / wrong optimization switch transformation to same function call

[b.buschinski at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113741

--- Comment #2 from Bernd Buschinski <b.buschinski at googlemail dot com> ---
Ah sorry, I did not know that. Please rephrase the topic to better match the
actual problem :)

(Or tell me what it should be rephrased to)

[Bug tree-optimization/113741] missed optimization switch transformation to same function call

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113741

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 96245.

*** This bug has been marked as a duplicate of bug 96245 ***