Subject: Re: altering a makefile
From: Murias O'Ceallagh (linux@dragonsblood.net)
Date: Mon May 21 2001 - 15:07:23 MDT
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I appreciate the pointers here. I tried a few things and it actually did
start compiling.. But ran into yet another difficulty.. the makefile
calls on nasm.. assembly for the 80x86 chipset. Is there a way around
this one, or at this should I cut my losses and try to find another
application for my purposes? Although, I must say I am getting some kind
of sick pleasure attempting to get this makefile to work for ppc. :)
~Murias
>--On Friday, May 18, 2001 05:28:42 PM -0700 Murias O'Ceallagh
><linux@dragonsblood.net> wrote:
>
>> CC=gcc -c -m486 -O3 -finline-functions -fomit-frame-pointer -funroll-loops
>> # This option is available for gcc-2.8.x
>> #CC=gcc -c -mcpu=pentiumpro -malign-double -O6 -fstrength-reduce
>> -fexpensive-optimizations -finline-functions -fomit-frame-p
>> ointer -funroll-loops
>> # This option is available for gcc-2.95.1, gcc-2.95.2, gcc-2.95.3,... on
>> P6 or later
>> #CC=gcc -c -mcpu=pentiumpro -march=pentiumpro -O9 -fstrength-reduce
>> -fexpensive-optimizations -finline-functions -fomit-frame
>> -pointer -funroll-loops -ffast-math -foptimize-register-move -fdefer-pop
>> -mfancy-math-387
>> CFLAGS=-Wall $(PROF) -DNDEBUG $(E3DN) $(VBR) -DRAW_INPUT
>
>>From the looks of the CFLAGS line, I'm guessing that the author of this
>code just played around with the optimizations until the code ran as fast
>as they wanted.
>
>Don't let the -f... options confuse you -- a lot of those are activated
>anyway once the optimization level (x in the '-Ox' option) is greater than
>a given threshold.
>
>One good way to get a starting point for optimization options is to look at
>some PPC-specific code in the kernel (RAID comes to mind as a good
>candidate, though I haven't looked recently). The thing is that you don't
>want to just throw in all of the available PPC optimization flags because
>there may be interactions between them (especially for very recent gcc
>snapshots).
>
>> From reading the man for gcc ( I am using 2.95.2) I was thinking about
>> uncommenting the last CC, then of course commenting out the first one,
>> replacing '-mcpu=pentiumpro' with -mcpu=ppc and deleting the
>> -march=pentiumpro.
>
>'-mcpu=ppc' is probably too general a choice for something
>performance-critical. If you're just trying to get this to run as fast as
>possible on your box, you can use your CPU type (the three-digit one, e.g.
>603e, 740, 750 -- cat /proc/cpuinfo for yours). Otherwise, you can hint the
>target processor type by using '-mtune=750' or whatever. See the gcc info
>page for details (Invoking GCC -> Submodel options -> RS/6000 and PowerPC
>Options).
>
>To get this to compile for the first time (and to give you a baseline for
>performance), you can just leave out the CC= def'n and you will get the
>default options (probably gcc -c).
>
>Depending on what this code is (and how much you want to dive into
>optimization) you may also want to look at profiling support (info gprof).
>
>--
>Charles Lepple <charles@ghz.cc>
>http://ghz.cc/charles/
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