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Re: [Emacs-diffs] trunk r117941: Default to stack objects on non-GNU/Lin

From: Paul Eggert
Subject: Re: [Emacs-diffs] trunk r117941: Default to stack objects on non-GNU/Linux, non-DOS_NT platforms.
Date: Thu, 25 Sep 2014 12:08:05 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.0

On 09/25/2014 11:12 AM, Stefan Monnier wrote:
I saw this extra checking in
local_cons, I figured this is going to kill too much of the
performance gain.

I agree that the performance gains are iffy, and would like to see some measurements here.

If it's any consolation, in some cases the new MAX_ALLOCA checking is optimized away. For example, other_buffer_safely calls build_local_string twice, both with constant literals, and in both cases my compiler (GCC 4.9.1 x86-64) deduces that there's no need to check for MAX_ALLOCA, and generates code that creates the Lisp string on the stack unconditionally.

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