libavutil: add x86 optimized av_popcount

Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavutil/intmath.h

@@ -29,6 +29,9 @@
 #if ARCH_ARM
 #   include "arm/intmath.h"
 #endif
+#if ARCH_X86
+#   include "x86/intmath.h"
+#endif
 
 /**
  * @addtogroup lavu_internal

libavutil/x86/intmath.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2015 James Almer
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_X86_INTMATH_H
+#define AVUTIL_X86_INTMATH_H
+
+#include <stdint.h>
+#include "config.h"
+
+/* Our generic version of av_popcount is faster than GCC's built-in on
+ * CPUs that don't support the popcnt instruction.
+ */
+#if defined(__GNUC__) && defined(__POPCNT__)
+    #define av_popcount   __builtin_popcount
+#if ARCH_X86_64
+    #define av_popcount64 __builtin_popcountll
+#endif
+
+#endif /* defined(__GNUC__) && defined(__POPCNT__) */
+
+#endif /* AVUTIL_X86_INTMATH_H */