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Re: bug#36370: 27.0.50; XFIXNAT called on negative numbers

From: Paul Eggert
Subject: Re: bug#36370: 27.0.50; XFIXNAT called on negative numbers
Date: Thu, 27 Jun 2019 14:13:14 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2

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.

Attachment: 0001-verify-tweak-assume-performance.patch
Description: Text Data

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