GMP treats pentium3 as i686, refuses to select mpn/x86/p6/p3mmx

Torbjorn Granlund tg at
Mon Aug 25 13:11:55 CEST 2008

buport at writes:

  This problem shows up when configuring gmp 4.2.2. Even when I explicitly
  say "./configure --build=pentium3-pc-linux-gnu", the configure script
  chooses i686 as the CPU type. The culprit is the line:
  ac_cv_host=`$ac_config_sub $ac_cv_host_alias`
  in the configure script, which runs config.sub to "canonicalize" the host
  type. Unfortunately, config.sub turns "pentium3" into "i686". As a result,
  the specialized code in mpn/x86/p6/p3mmx never gets selected, and we build
  only the generic p6 code instead.
  As a separate problem, config.guess does not have a special case for the
  Pentium3 either. It outputs "i686-pc-linux-gnu" even if the machine has a
  Pentium3 processor.

You basically report three problems.

1. The --build options doesn't work, you claim its value is overridden
2. That config.sub turns pentium3 to i686.
3. That config.guess doesn't have "a special case" for pentium3.

I now tested and looked at the 4.2.2 code, and I get confused.

The code looks right, and I tested all three claims on my systems, and
things work as they should.

Perhaps you have a modified gmp where somebody accidentally introduced
several bugs?  Or perhaps you're using a really old GMP (but these
fundamental things have probably work for at least the last 5 years
for pentium3).


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