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From: "jason at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/100409] C++ FE elides pure throwing call
Date: Thu, 08 Jul 2021 13:53:49 +0000 [thread overview]
Message-ID: <bug-100409-4-f7TV9kToUs@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-100409-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100409
--- Comment #13 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> - if (! TREE_SIDE_EFFECTS (expr))
> + if (! TREE_SIDE_EFFECTS (expr) && expr_noexcept_p (expr, 0))
> expr = void_node;
The assumption that an expression with TREE_SIDE_EFFECTS unset can be discarded
if its value is not used is made throughout the compiler. Abandoning that
invariant seems like a bad idea. And changing from checking a flag to walking
through the whole expression in all of those places sounds like an algorithmic
complexity problem.
If a pure/const function can throw, fine. But that shouldn't affect how
optimization treats the function call, or we'll end up pessimizing the vast
majority of calls to pure/const functions that don't throw (but are not
explicitly declared noexcept). In this testcase, if the user doesn't want the
compiler to optimize away a call to foo(), they shouldn't mark it pure.
next prev parent reply other threads:[~2021-07-08 13:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-04 6:45 [Bug c++/100409] New: " rguenth at gcc dot gnu.org
2021-05-04 6:46 ` [Bug c++/100409] " rguenth at gcc dot gnu.org
2021-05-05 8:02 ` rguenth at gcc dot gnu.org
2021-07-08 7:25 ` rguenth at gcc dot gnu.org
2021-07-08 8:19 ` harald at gigawatt dot nl
2021-07-08 8:38 ` rguenth at gcc dot gnu.org
2021-07-08 8:38 ` rguenth at gcc dot gnu.org
2021-07-08 8:39 ` rguenth at gcc dot gnu.org
2021-07-08 8:44 ` rguenth at gcc dot gnu.org
2021-07-08 9:17 ` harald at gigawatt dot nl
2021-07-08 9:20 ` rguenth at gcc dot gnu.org
2021-07-08 9:41 ` rguenth at gcc dot gnu.org
2021-07-08 13:15 ` mpolacek at gcc dot gnu.org
2021-07-08 13:53 ` jason at gcc dot gnu.org [this message]
2021-07-08 14:09 ` rguenth at gcc dot gnu.org
2021-07-08 15:13 ` jason at gcc dot gnu.org
2021-07-08 22:06 ` mpolacek at gcc dot gnu.org
2022-01-05 14:41 ` rguenth at gcc dot gnu.org
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