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From: Richard Biener <>
To: Jeff Law <>
Subject: Re: [RFA] Minor improvement to coremark, avoid unconditional jump to return
Date: Mon, 26 Sep 2022 09:53:41 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sun, Sep 25, 2022 at 6:29 PM Jeff Law <> wrote:
> This is a minor improvement for the core_list_find routine in coremark.
> Basically for riscv, and likely other targets, we can end up with an
> unconditional jump to a return statement.    This is a result of
> compensation code created by bb-reorder, and no jump optimization pass
> runs after bb-reorder to clean this stuff up.
> This patch utilizes preexisting code to identify suitable branch targets
> as well as preexisting code to emit a suitable return, so it's pretty
> simple.  Note that when we arrange to do this optimization, the original
> return block may become unreachable. So we conditionally call
> delete_unreachable_blocks to fix that up.
> This triggers ~160 times during an x86_64 bootstrap.  Naturally it
> bootstraps and regression tests on x86_64.
> I've also bootstrapped this on riscv64, regression testing with qemu
> shows some regressions, but AFAICT they're actually qemu bugs with
> signal handling/delivery -- qemu user mode emulation is not consistently
> calling user defined signal handlers.  Given the same binary, sometimes
> they'll get called and the test passes, other times the handler isn't
> called and the test (of course) fails. I'll probably spend some time to
> try and chase this down for the sake of making testing easier.
> OK for the trunk?



> Jeff

  reply	other threads:[~2022-09-26  7:53 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-25 16:28 Jeff Law
2022-09-26  7:53 ` Richard Biener [this message]
2022-10-07 10:51 ` Franz Sirl
2022-10-07 11:33   ` Richard Biener
2022-10-07 14:13   ` Jeff Law
2022-10-07 15:11     ` Franz Sirl

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