Code snippets
Note : Most of this is C code compiled with GCC.
C / Shell : Standalone single file compilation / execution
(self-executable C file)
A C / Shell trick to pack the code, compilation and execution
of a C program into a single file which is useful for short
programs, prototypes, debugging or to show off C examples, put this
into a test.c file and run it with sh test.c :
#ifdef d
#!/bin/sh
gcc -Wall -O0 test.c -o out
./out
exit
#endif
// your usual C code
C / x86 : SIMD debugging / exploration (with
intrinsics)
This is a program i did as an exploration / debugging tool
when i started to use SIMD instructions, it use compiler
intrinsics (see the
intrinsics guide) and just print the content of SIMD registers
(here AVX),
quite useful to quickly evaluate the result of some SIMD code. Just
put it into a simd.c file and run it with sh simd.c
:
#ifdef d
#!/bin/sh
gcc -Wall -mavx2 -m32 -O0 simd.c -o out
./out
exit
#endif
#include <stdio.h>
#include <x86intrin.h>
float input2[8] = {
0.75f, 0.5f, 0.25f, 0.0f
};
float output[8] = {
0
};
int main (void) {
__m256i i1i = _mm256_set_epi32(0, 0, 0, 0, 0, 6,
4, 2);
__m256 v1 = _mm256_cvtepi32_ps(i1i);
__m256 i2 = _mm256_loadu_ps(&input2[0]);
__m256 v2 = _mm256_mul_ps(v1, i2);
__m256 v3 = _mm256_hadd_ps(v2, v2);
_mm256_storeu_ps((float *)output, v3);
for (int i = 0; i < 8; i += 1) {
printf("%f ",
output[i]);
}
printf("\n");
return 0;
}
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