x86: Add a Yasm-based emms() replacement

This provides a fallback when building with Yasm enabled, but neither
inline assembly, nor the _mm_empty intrinsic are available or enabled.

Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavutil/internal.h

@@ -141,6 +141,9 @@ static av_always_inline void emms_c(void)
 #elif HAVE_MMX && HAVE_MM_EMPTY
 #   include <mmintrin.h>
 #   define emms_c _mm_empty
+#elif HAVE_MMX && HAVE_YASM
+#   include "libavutil/x86/emms.h"
+#   define emms_c avpriv_emms_yasm
 #else
 #   define emms_c()
 #endif /* HAVE_MMX_INLINE */

libavutil/x86/Makefile

@@ -2,4 +2,5 @@ OBJS += x86/cpu.o                                                       \
         x86/float_dsp_init.o                                            \
 
 YASM-OBJS += x86/cpuid.o                                                \
+             x86/emms.o                                                 \
              x86/float_dsp.o                                            \

libavutil/x86/emms.asm

@@ -0,0 +1,30 @@
+;*****************************************************************************
+;* Copyright (C) 2013 Martin Storsjo
+;*
+;* This file is part of Libav.
+;*
+;* Libav 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.
+;*
+;* Libav 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 Libav; if not, write to the Free Software
+;* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+;******************************************************************************
+
+%include "x86util.asm"
+
+SECTION .text
+
+;-----------------------------------------------------------------------------
+; void avpriv_emms_yasm(void)
+;-----------------------------------------------------------------------------
+cvisible emms_yasm, 0, 0
+    emms
+    RET

libavutil/x86/emms.h

@@ -0,0 +1,24 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_X86_EMMS_H
+#define AVUTIL_X86_EMMS_H
+
+void avpriv_emms_yasm(void);
+
+#endif /* AVUTIL_X86_EMMS_H */