[Dri-devel] SSE enabling revisited

[Gareth H. <ga...@va...>]

There are only two ways we can truly be safe in enabling the SSE code:

1) Read the CR4 register and test the OSFXSR/OSXMMEXCPT bits.  We can't
do this outside of the kernel.

2) Set up signal handler for SIGILL, execute an SSE instruction, and see
what happens.

Method 2 will verify if we can really turn the SSE code on, and all
other methods of testing are somewhat flawed and will lead to problems. 
I'll code this up tonight and commit it to the trunk and Mesa CVS.

Note that this test will only be done on Linux -- for all other OSes, if
the CPUID bit is set we'll enable the code.  Feel free to change this
behaviour.

-- Gareth