Re: [PATCH, i386]: Vectorize copysign for x86

[Uros Bizjak <ubizjak at gmail dot com>]

On 07/15/2009 05:45 PM, Richard Guenther wrote:
> > ï ï.section ï ï.rodata.cst16,"aM",@progbits,16
> > ï ï.align 16
> > .LC0:
> > ï ï.long ï ï2147483648
> > ï ï.long ï ï2147483648
> > ï ï.long ï ï2147483648
> > ï ï.long ï ï2147483648
> > ï ï.align 16
> >      
>
> 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.

Uros.