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https://github.com/cirosantilli/linux-kernel-module-cheat.git
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64 lines
2.4 KiB
C
64 lines
2.4 KiB
C
/* https://cirosantilli.com/linux-kernel-module-cheat#gcc-intrinsics */
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#include <assert.h>
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#include <string.h>
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#include <x86intrin.h>
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float global_input0[] __attribute__((aligned(16))) = {1.5f, 2.5f, 3.5f, 4.5f};
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float global_input1[] __attribute__((aligned(16))) = {5.5f, 6.5f, 7.5f, 8.5f};
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float global_output[4] __attribute__((aligned(16)));
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float global_expected[] __attribute__((aligned(16))) = {7.0f, 9.0f, 11.0f, 13.0f};
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int main(void) {
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/* 32-bit add (addps). */
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{
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__m128 input0 = _mm_set_ps(1.5f, 2.5f, 3.5f, 4.5f);
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__m128 input1 = _mm_set_ps(5.5f, 6.5f, 7.5f, 8.5f);
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__m128 output = _mm_add_ps(input0, input1);
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/* _mm_extract_ps returns int instead of float:
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* * https://stackoverflow.com/questions/5526658/intel-sse-why-does-mm-extract-ps-return-int-instead-of-float
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* * https://stackoverflow.com/questions/3130169/how-to-convert-a-hex-float-to-a-float-in-c-c-using-mm-extract-ps-sse-gcc-inst
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* so we must use instead: _MM_EXTRACT_FLOAT
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*/
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float f;
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_MM_EXTRACT_FLOAT(f, output, 3);
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assert(f == 7.0f);
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_MM_EXTRACT_FLOAT(f, output, 2);
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assert(f == 9.0f);
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_MM_EXTRACT_FLOAT(f, output, 1);
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assert(f == 11.0f);
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_MM_EXTRACT_FLOAT(f, output, 0);
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assert(f == 13.0f);
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/* And we also have _mm_cvtss_f32 + _mm_shuffle_ps, */
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assert(_mm_cvtss_f32(output) == 13.0f);
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assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 1)) == 11.0f);
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assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 2)) == 9.0f);
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assert(_mm_cvtss_f32(_mm_shuffle_ps(output, output, 3)) == 7.0f);
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}
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/* Now from memory. */
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{
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__m128 *input0 = (__m128 *)global_input0;
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__m128 *input1 = (__m128 *)global_input1;
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_mm_store_ps(global_output, _mm_add_ps(*input0, *input1));
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assert(!memcmp(global_output, global_expected, sizeof(global_output)));
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}
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/* 64-bit add (addpd). */
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{
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__m128d input0 = _mm_set_pd(1.5, 2.5);
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__m128d input1 = _mm_set_pd(5.5, 6.5);
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__m128d output = _mm_add_pd(input0, input1);
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/* OK, and this is how we get the doubles out:
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* with _mm_cvtsd_f64 + _mm_unpackhi_pd
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* https://stackoverflow.com/questions/19359372/mm-cvtsd-f64-analogon-for-higher-order-floating-point
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*/
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assert(_mm_cvtsd_f64(output) == 9.0);
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assert(_mm_cvtsd_f64(_mm_unpackhi_pd(output, output)) == 7.0);
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}
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return 0;
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}
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