[X-Unix] "Bad CPU type"

[Juan Manuel Palacios]

On Jun 14, 2004, at 12:36 PM, Victor Eijkhout wrote:

>> 	Aha! Here, this next line calls gcc with the "-fast" optimization 
>> flag. Well, it turns out that Apple's gcc default configuration 
>> causes this flag to produce binaries *exclusively" for the G5 
>> architecture... how do you like that??
>
> Thank you so much for finding that. I don't think I'd've found it on 
> my own.

	Hey, my pleasure! That's exactly what this mailing lists are for...

>
> I've now replaced "-fast" by "-O2" in the makefile. Simplest solution 
> and reasonably portable.

	You are correct my friend, "-O2" is more portable than "-fast 
-mcpu=7450" because, even though the latter encompasses the widest set 
of Apple architectures, it is still an Apple only optimization flag; a 
Makefile with those choices will fail miserably, say, on Linux. Have 
you considered the portable topmost "-O3" flag? Reportedly it is the 
highest optimization, though of course you may ask yourself if you 
really need it when you start encountering compilation time trade offs.

>
> If I understood the autoconf shit (:-/) better I would repair that: 
> from the log file you can clearly see that it compiles some test file 
> with "-fast", and if that succeeds it accepts the option. It should 
> actually run it.

	Can't say much here because, honestly, haven't even touched a single 
autoconf script in my life (read tons, of course)... some would praise 
me and say I'm smart for that, some would say I'm an ignorant newbie... 
maybe I'm both! :-) But the one thing I can tell you, is that such test 
would have succeeded on a G5 and your code would still  *not* be 
portable; so, as you wisely say, maybe just sticking to the "-O" set of 
optimization flags is the best solution

>
> Btw, elsewhere someone suggested doing "otool -h" on the executable. 
> That gave me (with /usr/include/mach/machine.h) the information that 
> the executable was for PowerPC 970.

	Which is exactly the technical name of the G5: cputype 18 
(CPU_TYPE_POWERPC) and cpusubtype 18 (CPU_SUBTYPE_POWERPC_970); with 
"-fast -mcpu=7450" the binary becomes cputype 18 and cpusubtype 0 
(CPU_SUBTYPE_POWERPC_ALL).

>
> Anyway. We're off and running. Thanks again!

	I'm glad you are, pleasure helping you! Regards,...


		Juan