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Re: Possibly OT: GCC 2.96 on PPC for VxWorks 5.5


%% John Clark <jclark@metricsystems.com> writes:

Thanks for replying, John!

  >> the Linux version of the compiler generates this assembly code:
  >> 
  >> mulli 9,0,100
  >> stw 9,28(31)
  >> 
  >> while the Solaris version generates this assembly code:
  >> 
  >> mr 11,0
  >> slwi 9,11,1
  >> add 9,9,0
  >> slwi 11,9,5
  >> add 9,9,11
  >> add 0,9,0
  >> stw 0,28(31)

  jc> I would conjecture that the above is due to some form of option
  jc> that selects a 'mul' over a shift and add implementation. That
  jc> could be based on machine type (ie which PPC implementation) or
  jc> optimizer settings, again conditioned on machine type, that the
  jc> new compiler defaults to.  (PPC things for me are pretty ancient,
  jc> but arn't there versions which don't have a multiply?)

Well, the compile lines I use to generate the .s files on both systems
are byte-for-byte identical, so it's not the command-line flags
(optimization levels, -f arch settings, etc.)  I've also looked at the
ccppc -v output and compared those: no differences.

The spec file that was installed for Linux was very different than the
one for Solaris.  However, I did try copying the Solaris spec file over
into the Linux compiler installation and that didn't help either.


I'm about out of ideas, other than the obvious: I have the wrong source
code :-/.

Any pointers to good sources of information on this subject?

-- 
-------------------------------------------------------------------------------
 Paul D. Smith <psmith@nortel.com>           HASMAT--HA Software Mthds & Tools
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist
-------------------------------------------------------------------------------
        These are my opinions--Nortel takes no responsibility for them.

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