Bug 42683 - gcc manpage: Description of x86 -march not clear regarding mmx
Summary: gcc manpage: Description of x86 -march not clear regarding mmx
Status: NEW
Alias: None
Product: gcc
Classification: Unclassified
Component: target (show other bugs)
Version: 4.4.2
: P3 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
Keywords: documentation
Depends on:
Reported: 2010-01-10 16:20 UTC by devurandom
Modified: 2010-02-07 19:51 UTC (History)
1 user (show)

See Also:
Known to work:
Known to fail:
Last reconfirmed: 2010-02-07 19:51:59


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Description devurandom 2010-01-10 16:20:05 UTC
The description of -march=i686/pentiumpro in the gcc manpage is:
i586, pentium
  Intel Pentium CPU with no MMX support.
  Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.
  Intel PentiumPro CPU.
  Same as "generic", but when used as "march" option, PentiumPro instruction set will be used, so the code will run on all i686 family chips.

In this context it is not clear whether i686 includes MMX support or not.
Checking Wikipedia suggests (though it is not clearly mentioned) that the PentiumPro contained no MMX support, which arrived only with the Pentium II.
Thus the description of "pentiumpro" should probably include "with no MMX support" as the description of "pentium" does.
Comment 1 Andrew Pinski 2010-02-07 19:51:59 UTC