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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114010] Unwanted effects of using SSA free lists.
Date: Thu, 22 Feb 2024 10:28:27 +0000	[thread overview]
Message-ID: <bug-114010-4-DT5PK9zk8N@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-114010-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114010

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's expected that SSA naming can affect code generation, there's no
"declaration order" as for VAR_DECLs we could ultimatively fall back to.

Ideally algorithms should not depend on particular ordering so it might be
good to investigate particular bad cases.

For that I'd even suggest to add a debug mechanism to "shuffle" SSA names
somewhat randomly (but note statements should be re-canonicalized
afterwards).

There are some cases with SLP vectorization of COND_EXPRs that are
problematic where both the false/true arms and the condition can
be "canonicalized" (yes, the inside the vectorizer COND_EXPRs with
embedded conditions are still a thing - thanks to pattern recog).

I don't know of any others.

  parent reply	other threads:[~2024-02-22 10:28 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-20 10:22 [Bug tree-optimization/114010] New: " manolis.tsamis at vrull dot eu
2024-02-21  0:06 ` [Bug tree-optimization/114010] " pinskia at gcc dot gnu.org
2024-02-21  0:11 ` pinskia at gcc dot gnu.org
2024-02-21  0:22 ` pinskia at gcc dot gnu.org
2024-02-21 12:03 ` manolis.tsamis at vrull dot eu
2024-02-21 12:09 ` manolis.tsamis at vrull dot eu
2024-02-22  1:02 ` ptomsich at gcc dot gnu.org
2024-02-22  1:02 ` ptomsich at gcc dot gnu.org
2024-02-22 10:28 ` rguenth at gcc dot gnu.org [this message]
2024-02-23 14:31 ` ptomsich at gcc dot gnu.org
2024-02-23 15:02 ` manolis.tsamis at vrull dot eu

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