[SCM] libav/experimental: x86: h264: Don't keep data in the redzone across function calls on 64 bit unix
siretart at users.alioth.debian.org
siretart at users.alioth.debian.org
Sun Aug 10 16:03:25 UTC 2014
The following commit has been merged in the experimental branch:
commit 570d4b21863b6254d6bbca9c528bede471bb4478
Author: Martin Storsjö <martin at martin.st>
Date: Mon Feb 20 11:24:35 2012 +0200
x86: h264: Don't keep data in the redzone across function calls on 64 bit unix
We know that the called function (ff_chroma_inter_body_mmxext)
doesn't touch the redzone, and thus will be kept intact - thus,
this doesn't fix any bug per se.
However, valgrind's memcheck tool intentionally assumes that the
redzone is clobbered on every function call and function return
(see a long comment in valgrind/memcheck/mc_main.c). This avoids
false positives in that tool, at the cost of an extra stack pointer
adjustment.
The other alternative would be a valgrind suppression for this issue,
but that's an extra burden for everybody that wants to run libavcodec
within valgrind.
Signed-off-by: Martin Storsjö <martin at martin.st>
diff --git a/libavcodec/x86/h264_deblock.asm b/libavcodec/x86/h264_deblock.asm
index 8a9fdf6..61642a0 100644
--- a/libavcodec/x86/h264_deblock.asm
+++ b/libavcodec/x86/h264_deblock.asm
@@ -821,10 +821,10 @@ cglobal deblock_v_chroma_8, 5,6
; int8_t *tc0)
;-----------------------------------------------------------------------------
cglobal deblock_h_chroma_8, 5,7
-%if UNIX64
- %define buf0 [rsp-24]
- %define buf1 [rsp-16]
-%elif WIN64
+%if ARCH_X86_64
+ ; This could use the red zone on 64 bit unix to avoid the stack pointer
+ ; readjustment, but valgrind assumes the red zone is clobbered on
+ ; function calls and returns.
sub rsp, 16
%define buf0 [rsp]
%define buf1 [rsp+8]
@@ -840,7 +840,7 @@ cglobal deblock_h_chroma_8, 5,7
movq m0, buf0
movq m3, buf1
TRANSPOSE8x4B_STORE PASS8ROWS(t5, r0, r1, t6)
-%if WIN64
+%if ARCH_X86_64
add rsp, 16
%endif
RET
--
Libav/FFmpeg packaging
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