· Florian Philipp <[EMAIL PROTECTED]>: > You see, they are not compatible and even if some code works I wouldn't bet > multimedia apps will perform well. > > With -mtune the instruction set stays the same. It is just "rearranged".
Hm. Allright. When using just -mtune (ie. without -march), the docs at http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/i386-and-x86_002d64-Options.html say: | While picking a specific cpu-type will schedule things appropriately | for that particular chip, the compiler will not generate any code that | does not run on the i386 without the -march=cpu-type option being used. If -mtune=athlon-xp is used, code is generated which may make use of 3dNOW!. 3dNOW! is, of course, not to be found on 386 :) If the instruction set stays the same, code generated with -mtune=athlon-xp would not be executable on 386 machines, if I understand you correctly. Hm. With -mtune, the set of available instructions (ie. stuff like 3dNOW!, I suppose?) is NOT changed from the default of i386, is it? Or what does "Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions." mean - especially note the "except for [...] the set of available instructions" part. So with "-mtune=pentium-m -march=athlon-xp" I'm making the compiler generate code which is "ordered" the way it's best for pentium-m machines while allowing it to use athlon-xp instruction set? Is that what I'm doing? If so, then it seems you're right - code will run, but maybe not so well. Is that understanding correct? If so, then I really should think twice about using "-mtune=pentium-m -march=athlon-xp", shouldn't I? Curious, Alexander Skwar -- No matter how many resources you have, it is never enough. -- Murphy's Computer Laws n�1 -- [EMAIL PROTECTED] mailing list
