Re: target/6882: [SPARC] Useless stack adjustment code

[Hans-Peter Nilsson <hp@bitrange.com>]

The following reply was made to PR target/6882; it has been noted by GNATS.

From: Hans-Peter Nilsson <hp@bitrange.com>
To: Eric Botcazou <ebotcazou@libertysurf.fr>
Cc: dann@godzilla.ics.uci.edu,  <gcc-bugs@gcc.gnu.org>,  <nobody@gcc.gnu.org>, 
     <gcc-gnats@gcc.gnu.org>
Subject: Re: target/6882: [SPARC] Useless stack adjustment code
Date: Mon, 31 Mar 2003 07:44:27 -0500 (EST)

 On Mon, 31 Mar 2003, Eric Botcazou wrote:
 
 > > No, it seems a valid optimization request to not emit the
 > > stack-adjustment code.  Could you find a *specific* reason for
 > > the stack-adjustment code?  (Please state that in the PR.)
 >
 > No, I don't see a "specific" reason. But:
 > - functions from the same translation unit that call it (and that appear
 > after it in normal mode, but the restriction is lifted with
 > -funit-at-a-time) don't actually emit the call,
 > - would the benefit be worth it in real life, given that the costly operation
 > is to call the function itself (for nothing)? I think the real optimization
 > is not to emit the call at all.
 
 Now you're arguing about the *value of the optimization*.
 I was arguing about *closing the PR for the wrong reason*.
 It seemed to indicate a misunderstanding about GCC rather than a
 special need on the SPARC.  For example, the CRIS and MMIX
 targets don't emit that kind of redundant stack frame.
 
 Having said that, let's continue to the *new* discussion.  You
 can't optimize out the call from other translation units.  Not
 being a SPARC maintainer I won't try to judge on the benefit,
 but it looks simple enough and seems worthwhile.  C++ tends to
 generate a lot of small trivial functions.
 
 brgds, H-P