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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/96846] [x86] Prefer xor/test/setcc over test/setcc/movzx sequence
Date: Sat, 29 Aug 2020 21:10:44 +0000	[thread overview]
Message-ID: <bug-96846-4-8UH7lGBu8A@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-96846-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96846

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
        mov     edx, DWORD PTR [rdi]
        cmp     edx, esi
        sete    al
        cmp     edx, r9d
        sete    dl
        or      eax, edx
        movzx   eax, al
This isn't what the peepholes are looking for, there are several other insns in
between, and peephole2s only work on exact insn sequences, doing anything more
complex would require doing it in some machine specific pass.
Note, while in theory it could add xor eax, eax before the cmp edx, esi insn,
it can't add xor edx, edx because the second comparison uses that register.

  parent reply	other threads:[~2020-08-29 21:10 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-29 17:47 [Bug target/96846] New: " andysem at mail dot ru
2020-08-29 19:39 ` [Bug target/96846] " jakub at gcc dot gnu.org
2020-08-29 20:53 ` andysem at mail dot ru
2020-08-29 21:10 ` jakub at gcc dot gnu.org [this message]
2020-08-29 21:34 ` andysem at mail dot ru

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