Re: PATCH: Add AVX support to x86-64 _dl_runtime_profile

[Ulrich Drepper <drepper at redhat dot com>]

H.J. Lu wrote:
> Since SSE registers are aliases of the lower 128bits of AVX register,
> we only need to restore AVX register if it is available.

No.  This would only work if we would have had the AVX registers in the
data structure from day one.  The current ABI allows audit modules to
modify the lr_xmm array and see the changes being reflected in the
program run.  You cannot after that fact require that the lr_ymm
registers have to be modified.

This is why this two-step process is needed.


> Since AVX register is just SSE register extended to 256bit, we only
> use the first 8 AVX/SSE registers for passing parameters.

This makes no sense.  There are 16 of them and if a function needs more
than 8 it should be able to use it.  Someone should fix gcc.


> Here is the updated patch tested under AVX emulator.

As said above, the restoring issue has to be addressed.


> It defines
> La_x86_64_vector as 64byte since we will extend 256bit AVX register
> to 512bit in the future.

OK I guess.

-- 
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â