[FFmpeg-devel] [PATCH] fix crash on AMD K6-3+

Mikulas Patocka mikulas at artax.karlin.mff.cuni.cz
Sun Nov 3 18:00:17 CET 2013


There are instructions pavgb and pavgusb. Both instructions do the same
operation but they have different enconding. Pavgb exists in SSE (or
MMXEXT) instruction set and pavgusb exists in 3D-NOW instruction set.

livavcodec uses the macro PAVGB to select the proper instruction. However,
the function avg_pixels8_xy2 doesn't use this macro, it uses pavgb

As a consequence, the function avg_pixels8_xy2 crashes on AMD K6-2 and 
K6-3 processors, because they have pavgusb, but not pavgb.

This bug seems to be introduced by commit 
71155d7b4157fee44c0d3d0fc1b660ebfb9ccf46, "dsputil: x86: Convert mpeg4 
qpel and dsputil avg to yasm"

Signed-off-by: Mikulas Patocka <mikulas at artax.karlin.mff.cuni.cz

 ffmpeg/libavcodec/x86/hpeldsp.asm |   26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

Index: mplayer/ffmpeg/libavcodec/x86/hpeldsp.asm
--- mplayer.orig/ffmpeg/libavcodec/x86/hpeldsp.asm	2013-11-03 02:26:15.000000000 +0100
+++ mplayer/ffmpeg/libavcodec/x86/hpeldsp.asm	2013-11-03 17:14:54.000000000 +0100
@@ -423,30 +423,30 @@ cglobal avg_pixels8_xy2, 4,5
     mova         m6, [pb_1]
     lea          r4, [r2*2]
     mova         m0, [r1]
-    pavgb        m0, [r1+1]
+    PAVGB        m0, [r1+1]
     mova         m2, [r1+r4]
     mova         m1, [r1+r2]
     psubusb      m2, m6
-    pavgb        m1, [r1+r2+1]
-    pavgb        m2, [r1+r4+1]
+    PAVGB        m1, [r1+r2+1]
+    PAVGB        m2, [r1+r4+1]
     add          r1, r4
-    pavgb        m0, m1
-    pavgb        m1, m2
-    pavgb        m0, [r0]
-    pavgb        m1, [r0+r2]
+    PAVGB        m0, m1
+    PAVGB        m1, m2
+    PAVGB        m0, [r0]
+    PAVGB        m1, [r0+r2]
     mova       [r0], m0
     mova    [r0+r2], m1
     mova         m1, [r1+r2]
     mova         m0, [r1+r4]
-    pavgb        m1, [r1+r2+1]
-    pavgb        m0, [r1+r4+1]
+    PAVGB        m1, [r1+r2+1]
+    PAVGB        m0, [r1+r4+1]
     add          r0, r4
     add          r1, r4
-    pavgb        m2, m1
-    pavgb        m1, m0
-    pavgb        m2, [r0]
-    pavgb        m1, [r0+r2]
+    PAVGB        m2, m1
+    PAVGB        m1, m0
+    PAVGB        m2, [r0]
+    PAVGB        m1, [r0+r2]
     mova       [r0], m2
     mova    [r0+r2], m1
     add          r0, r4

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