Add an AVX512 enabled DDOT function

written in C intrinsics for best readability.
(the same C code works for Haswell as well)

For logistical reasons the code falls back to the existing
haswell AVX2 implementation if the GCC or LLVM compiler is not new enough

diff --git a/kernel/x86_64/ddot.c b/kernel/x86_64/ddot.c
index 0dc9cd3..9693576 100644 (file)
--- a/kernel/x86_64/ddot.c
+++ b/kernel/x86_64/ddot.c
@@ -37,8 +37,10 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "ddot_microk_piledriver-2.c"
 #elif defined(NEHALEM)
 #include "ddot_microk_nehalem-2.c"
-#elif defined(HASWELL) || defined(ZEN) || defined (SKYLAKEX)
+#elif defined(HASWELL) || defined(ZEN)
 #include "ddot_microk_haswell-2.c"
+#elif defined (SKYLAKEX)
+#include "ddot_microk_skylakex-2.c"
 #elif defined(SANDYBRIDGE)
 #include "ddot_microk_sandy-2.c"
 #endif

diff --git a/kernel/x86_64/ddot_microk_skylakex-2.c b/kernel/x86_64/ddot_microk_skylakex-2.c
new file mode 100644 (file)
index 0000000..8eabf22
--- /dev/null
+++ b/kernel/x86_64/ddot_microk_skylakex-2.c
@@ -0,0 +1,96 @@
+/***************************************************************************
+Copyright (c) 2014, The OpenBLAS Project
+All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+1. Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in
+the documentation and/or other materials provided with the
+distribution.
+3. Neither the name of the OpenBLAS project nor the names of
+its contributors may be used to endorse or promote products
+derived from this software without specific prior written permission.
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE OPENBLAS PROJECT OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*****************************************************************************/
+
+/* need a new enough GCC for avx512 support */
+#if (( defined(__GNUC__)  && __GNUC__   > 6 && defined(__AVX2__)) || (defined(__clang__) && __clang_major__ >= 6))
+
+#define HAVE_KERNEL_8 1
+
+#include <immintrin.h>
+
+static void ddot_kernel_8( BLASLONG n, FLOAT *x, FLOAT *y, FLOAT *dot)
+{
+       int i = 0;
+       __m256d accum_0, accum_1, accum_2, accum_3;
+       
+       accum_0 = _mm256_setzero_pd();
+       accum_1 = _mm256_setzero_pd();
+       accum_2 = _mm256_setzero_pd();
+       accum_3 = _mm256_setzero_pd();
+
+#ifdef __AVX512CD__
+       __m512d accum_05, accum_15, accum_25, accum_35;
+       int n32;
+       n32 = n & (~31);
+
+       accum_05 = _mm512_setzero_pd();
+       accum_15 = _mm512_setzero_pd();
+       accum_25 = _mm512_setzero_pd();
+       accum_35 = _mm512_setzero_pd();
+
+       for (; i < n32; i += 32) {
+               accum_05 += _mm512_loadu_pd(&x[i+ 0]) * _mm512_loadu_pd(&y[i+ 0]);
+               accum_15 += _mm512_loadu_pd(&x[i+ 8]) * _mm512_loadu_pd(&y[i+ 8]);
+               accum_25 += _mm512_loadu_pd(&x[i+16]) * _mm512_loadu_pd(&y[i+16]);
+               accum_35 += _mm512_loadu_pd(&x[i+24]) * _mm512_loadu_pd(&y[i+24]);
+       }
+
+       /*
+        * we need to fold our 512 bit wide accumulator vectors into 256 bit wide vectors so that the AVX2 code
+        * below can continue using the intermediate results in its loop
+        */
+       accum_0 = _mm512_extractf64x4_pd(accum_05, 0) + _mm512_extractf64x4_pd(accum_05, 1);
+       accum_1 = _mm512_extractf64x4_pd(accum_15, 0) + _mm512_extractf64x4_pd(accum_15, 1);
+       accum_2 = _mm512_extractf64x4_pd(accum_25, 0) + _mm512_extractf64x4_pd(accum_25, 1);
+       accum_3 = _mm512_extractf64x4_pd(accum_35, 0) + _mm512_extractf64x4_pd(accum_35, 1);
+
+#endif
+       for (; i < n; i += 16) {
+               accum_0 += _mm256_loadu_pd(&x[i+ 0]) * _mm256_loadu_pd(&y[i+ 0]);
+               accum_1 += _mm256_loadu_pd(&x[i+ 4]) * _mm256_loadu_pd(&y[i+ 4]);
+               accum_2 += _mm256_loadu_pd(&x[i+ 8]) * _mm256_loadu_pd(&y[i+ 8]);
+               accum_3 += _mm256_loadu_pd(&x[i+12]) * _mm256_loadu_pd(&y[i+12]);
+       }
+
+       /* we now have the partial sums of the dot product in the 4 accumulation vectors, time to consolidate */
+
+       accum_0 = accum_0 + accum_1 + accum_2 + accum_3;
+
+       __m128d half_accum0;
+
+       /* Add upper half to lower half of each of the 256 bit vector to get a 128 bit vector */
+       half_accum0 = _mm_add_pd(_mm256_extractf128_pd(accum_0, 0), _mm256_extractf128_pd(accum_0, 1));
+
+       /* in 128 bit land there is a hadd operation to do the rest of the element-wise sum in one go */
+       half_accum0 = _mm_hadd_pd(half_accum0, half_accum0);
+
+       *dot = half_accum0[0];
+}
+
+#else
+#include "ddot_microk_haswell-2.c"
+#endif