Add an AVX512 enabled DGEMV (n) 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

kernel/x86_64/dgemv_n_4.c

@@ -31,8 +31,10 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #if defined(NEHALEM)
 #include "dgemv_n_microk_nehalem-4.c"
-#elif defined(HASWELL) || defined(ZEN) || defined(STEAMROLLER) || defined(EXCAVATOR) || defined (SKYLAKEX)
+#elif defined(HASWELL) || defined(ZEN) || defined(STEAMROLLER) || defined(EXCAVATOR)
 #include "dgemv_n_microk_haswell-4.c"
+#elif  defined (SKYLAKEX)
+#include "dgemv_n_microk_skylakex-4.c"
 #endif
 
 

kernel/x86_64/dgemv_n_microk_skylakex-4.c

@@ -0,0 +1,126 @@
+/***************************************************************************
+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_4x4 1
+
+#include <immintrin.h>
+
+static void dgemv_kernel_4x4( BLASLONG n, FLOAT **ap, FLOAT *x, FLOAT *y, FLOAT *alpha)
+{
+
+	int i = 0;
+
+	__m256d x0, x1, x2, x3;
+	__m256d __alpha;
+
+	x0 = _mm256_broadcastsd_pd(_mm_load_sd(&x[0]));
+	x1 = _mm256_broadcastsd_pd(_mm_load_sd(&x[1]));
+	x2 = _mm256_broadcastsd_pd(_mm_load_sd(&x[2]));
+	x3 = _mm256_broadcastsd_pd(_mm_load_sd(&x[3]));
+
+	__alpha = _mm256_broadcastsd_pd(_mm_load_sd(alpha));
+
+#ifdef __AVX512CD__
+	int n5;
+	__m512d x05, x15, x25, x35;
+	__m512d __alpha5;
+	n5 = n & ~7;
+
+	x05 = _mm512_broadcastsd_pd(_mm_load_sd(&x[0]));
+	x15 = _mm512_broadcastsd_pd(_mm_load_sd(&x[1]));
+	x25 = _mm512_broadcastsd_pd(_mm_load_sd(&x[2]));
+	x35 = _mm512_broadcastsd_pd(_mm_load_sd(&x[3]));
+
+	__alpha5 = _mm512_broadcastsd_pd(_mm_load_sd(alpha));
+
+	for (; i < n5; i+= 8) {
+		__m512d tempY;
+		__m512d sum;
+
+		sum = _mm512_loadu_pd(&ap[0][i]) * x05 +
+		      _mm512_loadu_pd(&ap[1][i]) * x15 +
+		      _mm512_loadu_pd(&ap[2][i]) * x25 +
+		      _mm512_loadu_pd(&ap[3][i]) * x35;
+
+		tempY = _mm512_loadu_pd(&y[i]);
+		tempY += sum *  __alpha5;
+		_mm512_storeu_pd(&y[i], tempY);
+	}
+#endif
+
+	for (; i < n; i+= 4) {
+		__m256d tempY;
+		__m256d sum;
+
+		sum = _mm256_loadu_pd(&ap[0][i]) * x0 +
+		      _mm256_loadu_pd(&ap[1][i]) * x1 +
+		      _mm256_loadu_pd(&ap[2][i]) * x2 +
+		      _mm256_loadu_pd(&ap[3][i]) * x3;
+
+		tempY = _mm256_loadu_pd(&y[i]);
+		tempY += sum *  __alpha;
+		_mm256_storeu_pd(&y[i], tempY);
+	}
+
+} 
+
+
+#define HAVE_KERNEL_4x2
+
+static void dgemv_kernel_4x2( BLASLONG n, FLOAT **ap, FLOAT *x, FLOAT *y, FLOAT *alpha)
+{
+
+	int i = 0;
+
+	__m256d x0, x1;
+	__m256d __alpha;
+
+	x0 = _mm256_broadcastsd_pd(_mm_load_sd(&x[0]));
+	x1 = _mm256_broadcastsd_pd(_mm_load_sd(&x[1]));
+
+	__alpha = _mm256_broadcastsd_pd(_mm_load_sd(alpha));
+
+
+	for (i = 0; i < n; i+= 4) {
+		__m256d tempY;
+		__m256d sum;
+
+		sum = _mm256_loadu_pd(&ap[0][i]) * x0 + _mm256_loadu_pd(&ap[1][i]) * x1;
+
+		tempY = _mm256_loadu_pd(&y[i]);
+		tempY +=  sum *  __alpha;
+		_mm256_storeu_pd(&y[i], tempY);
+	}
+
+}
+
+#else
+#include "dgemv_n_microk_haswell-4.c"
+#endif