__builtin_ia32_cvtb2mask512() is the GNU C builtin for vpmovb2m k, zmm.
The Intel intrinsic for it is _mm512_movepi8_mask.
It extracts the most-significant bit from each byte, producing an integer mask.
The SSE2 and AVX2 instructions pmovmskb and vpmovmskb do the same thing for 16 or 32-byte vectors, producing the mask in a GPR instead of an AVX-512 mask register. (_mm_movemask_epi8 and _mm256_movemask_epi8).
I would like an implementation for ARM that is faster than below
I would like an implementation for ARM NEON
I would like an implementation for ARM SVE
I have attached a basic scalar implementation in C. For those trying to implement this in ARM, we care about the high bit, but each byte's high bit (in a 128bit vector), can be easily shifted to the low bit using the ARM NEON intrinsic: vshrq_n_u8(). Note that I would prefer not to store the bitmap to memory, it should just be the return value of the function similar to the following function.
#define _(n) __attribute((vector_size(1<<n),aligned(1)))
typedef char V _(6); // 64 bytes, 512 bits
typedef unsigned long U;
#undef _
U generic_cvtb2mask512(V v) {
U mask=0;int i=0;
while(i<64){
// shift mask by 1 and OR with MSB of v[i] byte
mask=(mask<<1)|((v[i]&0x80)>>7);
i++;}
return mask;
}
This is also a dup of : https://stackoverflow.com/questions/79225312
Topic:
Graphics & Games
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