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Re: [PATCH] PPC64 Use hardware sqrt.


Steve Munroe writes:

> Paul do you agree to adding PPC_FEATURE_HAS_FPU_OPT to AT_HWCAP?

Yes, that would be fine.

I assume that means that new glibc running on an old kernel will not
use the optional FP instructions, i.e. the bit will bit 1 to say that
the optional instructions are implemented.

> For current PPC64 processors it will always be true. If/when a PPC64
> processor is shipped that does implement the full set of the Optional FP
> instructions we will need to add logic for the kernel to detect this. I
> suspect the landscape is more complex for PPC32.

I'm not aware of any 32-bit PowerPC processor that implements all of
the optional FP instructions.  The 74xx processors implement fsel,
fres and fsqrte.  I think we will just leave the bit at 0 in 32-bit
kernels.

I assume you're going to make a 32-bit glibc use the optional
instructions if available, so that we see the speedup for 32-bit
applications running on a 64-bit processor?

Regards,
Paul.


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