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From: "liuhongt at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113744] Unnecessary "m" constraint in *adddi_4
Date: Sun, 04 Feb 2024 03:06:02 +0000 [thread overview]
Message-ID: <bug-113744-4-sy5Qy4s6V7@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-113744-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113744
Hongtao Liu <liuhongt at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |liuhongt at gcc dot gnu.org
--- Comment #2 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
7018; For comparisons against 1, -1 and 128, we may generate better code
7019; by converting cmp to add, inc or dec as done by peephole2. This pattern
7020; is matched then. We can't accept general immediate, because for
7021; case of overflows, the result is messed up.
7022; Also carry flag is reversed compared to cmp, so this conversion is valid
7023; only for comparisons not depending on it.
7024
It sounds to me those peephole2 can be extended to memory operand since APX_NDD
supports that. So it's not redudant m constraint in the pattern, but miss
optimization in those peepholes.
prev parent reply other threads:[~2024-02-04 3:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-03 14:58 [Bug target/113744] New: " hjl.tools at gmail dot com
2024-02-03 15:00 ` [Bug target/113744] " hjl.tools at gmail dot com
2024-02-04 3:06 ` liuhongt at gcc dot gnu.org [this message]
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