From: Jeff Law <jeffreyalaw@gmail.com>
To: Richard Biener <rguenther@suse.de>, gcc-patches@gcc.gnu.org
Cc: Jakub Jelinek <jakub@redhat.com>
Subject: Re: [PATCH] tree-optimization/109237 - last_stmt is possibly slow
Date: Sun, 26 Mar 2023 12:00:11 -0600 [thread overview]
Message-ID: <d9a8b2d5-57e8-21f6-6ace-c6f650bbaee8@gmail.com> (raw)
In-Reply-To: <20230322123006.A480C3858296@sourceware.org>
On 3/22/23 06:29, Richard Biener via Gcc-patches wrote:
> Most uses of last_stmt are interested in control transfer stmts
> and for the testcase gimple_purge_dead_eh_edges shows up in
> the profile. But last_stmt looks past trailing debug stmts but
> those would be rejected by GIMPLEs verify_flow_info. The following
> adds possible_ctrl_stmt besides last_stmt which does not look
> past trailing debug stmts and adjusts gimple_purge_dead_eh_edges.
>
> I've put checking code into possible_ctrl_stmt that it will not
> miss a control statement if the real last stmt is a debug stmt.
>
> The alternative would be to change last_stmt, explicitely introducing
> last_nondebug_stmt. I remember we chickened out and made last_stmt
> conservative here but not anticipating the compile-time issues this
> creates. I count 227 last_stmt and 12 last_and_only_stmt uses.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> Any opinions? I probably lean towards s/last_stmt/last_nondebug_stmt/
> in next stage1 and then adding last_stmt and changing some
> uses back - through for maintainance that's going to be a
> nightmare (or maybe not, a "wrong" last_stmt should be safe to
> backport and a last_nondebug_stmt will fail to build).
Sounds quite sensible to me. 227+12 isn't terrible and I bet the vast
majority, should be safe for last_nondebug_stmt.
>
> Richard.
>
> PR tree-optimization/109237
> * tree-cfg.h (possible_ctrl_stmt): New function returning
> the last stmt not skipping debug stmts.
> (gimple_purge_dead_eh_edges): Use it.
OK
jeff
next parent reply other threads:[~2023-03-26 18:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20230322123006.A480C3858296@sourceware.org>
2023-03-26 18:00 ` Jeff Law [this message]
[not found] <20230322123020.B9718385B533@sourceware.org>
2023-03-22 16:50 ` Bernhard Reutner-Fischer
[not found] <90515.123032208295400168@us-mta-397.us.mimecast.lan>
2023-03-22 12:38 ` Jakub Jelinek
2023-03-22 12:29 Richard Biener
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