From: Jakub Jelinek <jakub@redhat.com>
To: Siddhesh Poyarekar <siddhesh@gotplt.org>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH v2] tree-object-size: Make unknown a computation
Date: Tue, 19 Oct 2021 09:45:57 +0200 [thread overview]
Message-ID: <20211019074557.GK304296@tucnak> (raw)
In-Reply-To: <20211019073830.303140-1-siddhesh@gotplt.org>
On Tue, Oct 19, 2021 at 01:08:30PM +0530, Siddhesh Poyarekar wrote:
> Compute the unknown size value as a function of the min/max bit of
> object_size_type. This transforms into a neat little branchless
> sequence on x86_64:
>
> movl %edi, %eax
> sarl %eax
> xorl $1, %eax
> negl %eax
> cltq
>
> which should be faster than loading the value from memory. A quick
> unscientific test using
>
> `time make check-gcc RUNTESTFLAGS="dg.exp=builtin*"`
>
> shaves about half a second off execution time with this. Also simplify
> implementation of unknown_object_size.
>
> gcc/ChangeLog:
>
> * tree-object-size.c (unknown): Make into a function. Adjust
> all uses.
> (unknown_object_size): Simplify implementation.
>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>
Ok for trunk if it passes bootstrap/regtest.
Jakub
next prev parent reply other threads:[~2021-10-19 7:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 4:17 [PATCH] " Siddhesh Poyarekar
2021-10-19 6:58 ` Jakub Jelinek
2021-10-19 7:28 ` Siddhesh Poyarekar
2021-10-19 7:38 ` [PATCH v2] " Siddhesh Poyarekar
2021-10-19 7:45 ` Jakub Jelinek [this message]
2021-10-20 3:00 ` Siddhesh Poyarekar
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