GNU bug report logs - #36370
27.0.50; XFIXNAT called on negative numbers

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Message #33 received at 36370 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Pip Cet <pipcet <at> gmail.com>
Cc: 36370 <at> debbugs.gnu.org, Gnulib bugs <bug-gnulib <at> gnu.org>
Subject: Re: bug#36370: 27.0.50; XFIXNAT called on negative numbers
Date: Thu, 27 Jun 2019 14:13:14 -0700

[Message part 1 (text/plain, inline)]

On 6/27/19 12:56 PM, Pip Cet wrote:

> The eassume tells GCC i is nonnegative, since (!(i >= 0) == !(i >= 0))
> is indeed a constant.

Ah! Thanks, I didn't catch that subtle point. Would the attached patch 
to verify.h address that problem? This patch is for Gnulib, but would 
propagate into Emacs.

I tried this out with Emacs master and although it did change the 
machine code subtly I didn't have the patience to see whether the 
changes were likely to improve performance. The changes did grow the 
Emacs text segment from 2556193 to 2557657 bytes (a 0.06% growth), which 
is not a good sign. This was on Fedora 30 x86-64 with a default Emacs build.

I'll CC: this to bug-gnulib since it's a Gnulib issue. I have not 
installed this patch into Gnulib on savannah.

[0001-verify-tweak-assume-performance.patch (text/x-patch, attachment)]

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