This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

RE: GCC 3.3.5: -march=i586 does not use all pentium FPU instructions


> -----Original Message-----
> From: 'Jonathan Wakely' 
> Sent: 11 February 2005 17:06

> Debating the difference between Pentium, pentium, i586 etc. 
> is off-topic
> and that is what I was drawing attention to - GCC doesn't 
> distinguish so
> the mail I replied to was unhelpful in making the distinction.

  Apart from the fact that it is a unique enough occasion to have seen Sam post
something technically accurate that it would be worthy of comment even if it was
discussing butter-churning techniques, I think that if we refer back to the OP's
question:

> I was wondering why the above gcc parameter does not enable the use of the
> fst/fld opcodes for pentium processors, while -march=i686 does. The Intel
> manuals specifically say that they can be used across all pentium processors.

it is entirely appropriate to point out that -march=i586 tunes the output to be
suitable for a larger group of processors than just the intel ones.  Therefore
there may be additional constraints that the OP could not have deduced from
reading the specs for the Intel manuals.

  Didn't the Cyrix series always have pretty poor FP support compared to the
others?

    cheers, 
      DaveK
-- 
Can't think of a witty .sigline today....


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]