Message-Id: Comments: Authenticated sender is From: "Salvador Eduardo Tropea (SET)" Organization: INTI To: lubaldo AT adinet DOT com DOT uy, djgpp AT delorie DOT com Date: Fri, 31 Jul 1998 10:13:22 +0000 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: -m and -march= switches and a 5x86... In-reply-to: <3.0.1.32.19980730202035.007a4c80@adinet.com.uy> Precedence: bulk lubaldo AT adinet DOT com DOT uy wrote: > I have GCC 2.8.1 installed. > I have tryed the -m386, -m486, -mpentium and -mpentiumpro switches and > they generate the exact same code... why is that? I tried -mpentiumpro and the code miserably(?) died with SIGILL because gcc used the conditional assigment instruction (P6 core only). Are you sure the assembler generated doesn't have even 1 line of difference? What are you compiling? > I have tryed the -march=586 switch. It produces Pentium code that it is > not compatible with earlyer CPU's, like 486, 386... but it works on my > machine! Who said GCC produces code that doesn't run in 486 when you use 586? Is in the manuals? I think gcc only changes the instruction order and aligment. What P5 instruction is used? > I have an AMD 5x86 processor, to my knowledge, this is a 486DX > compatible processor but it is not meant to be Pentium compatible... True. > so what? Yes, so what? ;-))) > I have tryed also the -march=686 and that it doesn't work and thats > Ok... And the code produced by GCC with the -march=586 directive is > different from the one produced with the -march=486 directive... so: I > don't understand why it works... someone knows something? I think is just reordered to exploit the P5 pipes, that's all. > I hope I am not bothering too much with my silly intrigues... Why? I saw worst ;-))) SET P.S. He is my friend, some answers are jokes. ------------------------------------ 0 -------------------------------- Visit my home page: http://set-soft.home.ml.org/ or http://www.geocities.com/SiliconValley/Vista/6552/ Salvador Eduardo Tropea (SET). (Electronics Engineer) Alternative e-mail: set-soft AT usa DOT net set AT computer DOT org ICQ: 2951574 Address: Curapaligue 2124, Caseros, 3 de Febrero Buenos Aires, (1678), ARGENTINA TE: +(541) 759 0013