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Re: [PATCH, i386]: Vectorize copysign for x86
On Wed, Jul 15, 2009 at 05:53:54PM +0200, Uros Bizjak wrote:
> On 07/15/2009 05:45 PM, Richard Guenther wrote:
> >Generating these kind of constants may be smaller and faster if
> >we use some arithmetic tricks. Do we have some generic routine
> >that could be used to materialize special constants?
>
> We can generate {0, 0, 0, 0} using pxor and {-1, -1, -1, -1} using
> pcmpeqd, see standard_sse_constant_opcode and friends in
> config/i386/i386.c. Although { 0x8000, 0x8000, 0x8000, 0x8000 } looks
> quite promising, I don't know of any simple way to directly materialize
> these kinds of constants in the register.
You can just do:
pcmpeqd xmm, xmm
pslld xmm, 31
(assuming you meant 0x80000000 in the vector above) can't you?
-Nathan