1 files changed, 96 insertions, 0 deletions
diff --git a/sysdeps/x86_64/fpu/multiarch/x86-math-features.c b/sysdeps/x86_64/fpu/multiarch/x86-math-features.c
new file mode 100644
index 0000000000..e803b73229
--- /dev/null
+++ b/sysdeps/x86_64/fpu/multiarch/x86-math-features.c
@@ -0,0 +1,96 @@
+/* Initialize CPU features for use by the math library.
+   This file is part of the GNU C Library.
+   Copyright (C) 2008-2018 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <x86-math-features.h>
+#include <atomic.h>
+#include <cpuid.h>
+#include <cpu-features.h>
+#include <stdbool.h>
+
+static unsigned int features;
+
+unsigned int
+__x86_math_features (void)
+{
+  unsigned int features_local = atomic_load_relaxed (&features);
+  if (features_local != 0)
+    /* At least the initialization bit is set, which means that we
+       have a proper value.  */
+    return features_local;
+
+  /* Perform initialization.  */
+  features_local = x86_math_feature_initialized;
+
+  unsigned int eax, ebx, ecx, edx;
+  unsigned int max_cpuid;
+  __cpuid (0, max_cpuid, ebx, ecx, edx);
+  bool cpu_amd = ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65;
+
+  if (max_cpuid >= 7)
+    {
+      __cpuid (1, eax, ebx, ecx, edx);
+      bool flag_fma = ecx & bit_cpu_FMA;
+      bool flag_osxsave = ecx & bit_cpu_OSXSAVE;
+      bool flag_avx = ecx & bit_cpu_AVX;
+      bool flag_sse41 = ecx & bit_cpu_SSE4_1;
+
+      if (flag_sse41)
+        features_local |= x86_math_feature_sse41;
+
+      __cpuid_count (7, 0, eax, ebx, ecx, edx);
+      bool flag_avx2 = ebx & bit_cpu_AVX2;
+
+      if (flag_osxsave)
+        {
+          unsigned int xcrlow;
+          unsigned int xcrhigh;
+          asm ("xgetbv" : "=a" (xcrlow), "=d" (xcrhigh) : "c" (0));
+          bool ymm_xmm_usable
+            = (xcrlow & (bit_YMM_state | bit_XMM_state))
+              == (bit_YMM_state | bit_XMM_state);
+
+          /* Is YMM and XMM state usable?  */
+          if (ymm_xmm_usable)
+            {
+              if (flag_avx)
+                {
+                  features_local |= x86_math_feature_avx;
+                  if (flag_avx2)
+                    features_local |= x86_math_feature_avx2;
+                  if (flag_fma)
+                    features_local |= x86_math_feature_fma;
+
+                  if (cpu_amd)
+                    {
+                      __cpuid (0x80000000, eax, ebx, ecx, edx);
+                      if (eax >= 0x80000001)
+                        {
+                          __cpuid (0x80000001, eax, ebx, ecx, edx);
+                          bool flag_fma4 = ecx & bit_cpu_FMA4;
+                          if (flag_fma4)
+                            features_local |= x86_math_feature_fma4;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+  atomic_store_relaxed (&features, features_local);
+  return features_local;
+}