Any SIMD experts?

[John Colvin via Digitalmars-d]

On Monday, 8 December 2014 at 16:32:50 UTC, Martin Nowak wrote:
> I want to do bounds checking of 2 (4 on avx) ulongs (64-bit) at 
> a time.
>
> ulong2 vval = [v0, v1];
> ulong2 vlow = [low, low];
> ulong2 vhigh = [high, high];
>
> int res = PMOVMSKB(vval >= vlow & vval < vhigh);
>
> I figured out sort of a solution, but it seems way too 
> complicated, because there is only signed comparison.
>
> Usually (scalar) I'd use this, which makes use of unsigned wrap 
> to safe one conditional
>
> immutable size = cast(ulong)(vhigh - vlow);
> if (cast(ulong)(v0 - vlow) < size) {}
> if (cast(ulong)(v1 - vlow) < size) {}
>
> over
>
> if (v0 >= vlow && v0 < vhigh) {}
>
> Maybe this can be used on SIMD too (saturated sub or so)?
>
> -Martin

Well gcc gives me:

typedef unsigned long ulong4 __attribute__ ((vector_size (32)));

ulong4 foo(ulong4 a, ulong4 l, ulong4 h)
{
     return (a >= l) & (a < h);
}


foo(unsigned long __vector, unsigned long __vector, unsigned long 
__vector):
	vmovdqa	.LC0(%rip), %ymm3
	vpsubq	%ymm3, %ymm0, %ymm0
	vpsubq	%ymm3, %ymm2, %ymm2
	vpsubq	%ymm3, %ymm1, %ymm1
	vpcmpgtq	%ymm0, %ymm2, %ymm2
	vpcmpgtq	%ymm0, %ymm1, %ymm1
	vpandn	%ymm2, %ymm1, %ymm0
	ret
.LC0:
	.quad	-9223372036854775808
	.quad	-9223372036854775808
	.quad	-9223372036854775808
	.quad	-9223372036854775808