Date: Sun, 18 Feb 2001 18:40:04 +0100 From: Marc Lehmann To: pgcc AT delorie DOT com Subject: Re: Probably pgcc-2.95.2.1 does not optimized propertly? Message-ID: <20010218184004.B2821@cerebro.laendle> Mail-Followup-To: pgcc AT delorie DOT com References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: ; from nickols_k@mail.ru on Sun, Feb 18, 2001 at 07:00:21PM +0000 X-Operating-System: Linux version 2.4.1 (root AT cerebro) (gcc version 2.95.2.1 19991024 (release)) Reply-To: pgcc AT delorie DOT com Errors-To: nobody AT delorie DOT com X-Mailing-List: pgcc AT delorie DOT com X-Unsubscribes-To: listserv AT delorie DOT com Precedence: bulk On Sun, Feb 18, 2001 at 07:00:21PM +0000, Nick Kurshev wrote: > But code which is produced in last case probably will be executed much faster of first (and it is smaller). please benchmark. "probably" is always wrong, especially when quoting out of the amd optimization manual. The way to go, usually, is to implement the exact opposite of what is in the manual. I am quite fed-up with AMD since I invested quite some time in implementing some of their suggestions (for AMD-K6) only to find out code gets slower. Especially their mmx unit is the biggets joke ever heard :( > Avoid long instruction length Use x86 instructions that are > less than eight bytes in length. An x86 instruction that is longer > > Clear registers using MOV reg, 0 instead of XOR reg, reg is mov 0, reg longer than seven bytes? -- -----==- | ----==-- _ | ---==---(_)__ __ ____ __ Marc Lehmann +-- --==---/ / _ \/ // /\ \/ / pcg AT goof DOT com |e| -=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+ The choice of a GNU generation | |