Intel CPUs these days have f16c feature flag, which enables native float16 support. Clang has support for foat16 via LLVM already, specifically this compiles and runs on several recent Intel CPUs:
#include <stdio.h>
void foo(_Float16 *a, _Float16 *b, _Float16 *restrict c) {
for (int i = 0; i < 8; ++i)
c[i] = a[i] + b[i];
}
int main (){
_Float16 a[8] ={0,1,2,3,4,5,6,7};
_Float16 c [8]= {0,0,0,0,0,0,0,0};
foo(&a, &a, &c);
printf("%f %f %f\n", (double)c[0], (double)c[1], (double)c[2]);
}
Obviously, the for loop in function foo gets vectorized as follows:
foo:
vcvtph2ps (%rsi), %ymm0 # load a
vcvtph2ps (%rdi), %ymm1 # load b
vaddps %ymm0, %ymm1, %ymm0 # actually add
vcvtps2ph $4, %ymm0, (%rdx) # store into c
vzeroupper
retq
Would it not be wise for rust to support float16 now that LLVM actually supports it properly? Its not like there is a need for some crazy involved new syntax or anything like that.
Intel's announcement from a year ago on the subject
PS: This subject has been raised before, and in all cases it boiled down to lack of hardware support.