Re: Pentium M config option for 2.6

From: Amit Gurdasani
Date: Mon Jan 05 2004 - 10:10:04 EST


:On Date: Sun, 4 Jan 2004 13:33:58 +0100, Tomas Szepe wrote:
:> > IOW, don't lie to the compiler and pretend P-M == P4
:> > with that -march=pentium4.
:>
:> What do you recommend to use as march then? There is
:> no pentiumm subarch support in gcc yet; I was convinced
:> p4 was the closest match.
:
:march=pentium3 is the closest safe choice, at least
:until gcc implements P-M specific support.
:
:/Mikael

Perhaps -mcpu=pentium3 -march=pentium4 would be a good compromise? From the
GCC 3.3 info pages:

`-mcpu=CPU-TYPE'
Tune to CPU-TYPE everything applicable about the generated code,
except for the ABI and the set of available instructions. [...]

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. [...]

`-march=CPU-TYPE'
Generate instructions for the machine type CPU-TYPE. The choices
for CPU-TYPE are the same as for `-mcpu'. Moreover, specifying
`-march=CPU-TYPE' implies `-mcpu=CPU-TYPE'.

Amit
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