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
I don't quite understand what you mean by "save one conditional".