Re: [PATCH, i386] Enable x86_ext_80387_constants for m_K8, m_CORE2 and m_GENERIC64

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 11/26/06, Uros Bizjak <ubizjak@gmail.com> wrote:
> Hello!
>
> This patch enables special x87 instructions to load extended constants
> for K8, CORE2 and generic 64 target. Loading of XF constant (fldt insn)
> on K8 costs 10 cycles (fldt is also a vector path instruction!), where
> all constant load insns are direct patch instructions having 4 cycle
> latency.

The only other notable difference (apart from the above positive) is that
fld mem80 seems to use the FMUL/FADD pipes while the special instructions
use FSTORE on the K8.  I don't know if this will make a difference in
practice, though.

Richard.