On Monday, 4 September 2017 at 23:06:27 UTC, Nicholas Wilson
wrote:
On Monday, 4 September 2017 at 20:39:11 UTC, Igor wrote:
I found that I can't use __simd function from core.simd under
LDC
Correct LDC does not support the core.simd interface.
and that it has ldc.simd but I couldn't find how to implement
equivalent to this with it:
ubyte16* masks = ...;
foreach (ref c; pixels) {
c = __simd(XMM.PSHUFB, c, *masks);
}
I see it has shufflevector function but it only accepts
constant masks and I am using a variable one. Is this possible
under LDC?
You have several options:
* write a regular for loop and let LDC's optimiser take care of
the rest.
alias mask_t = ReturnType!(equalMask!ubyte16);
pragma(LDC_intrinsic, "llvm.masked.load.v16i8.p0v16i8")
ubyte16 llvm_masked_load(ubyte16* val,int align, mask_t
mask, ubyte16 fallthru);
ubyte16* masks = ...;
foreach (ref c; pixels) {
auto mask = equalMask!ubyte16(*masks, [-1,-1,-1, ...]);
c = llvm_masked_load(&c,16,mask, [0,0,0,0 ... ]);
}
The second one might not work, because of type differences in
llvm, but should serve as a guide to hacking the `cmpMask` IR
code in ldc.simd to do what you want it to.
BTW. Shuffling channels within pixels using DMD simd is about
5 times faster than with normal code on my machine :)
Don't underestimate ldc's optimiser ;)
I seen cases where the compiler fail to optimized for smid.
