[FFmpeg-cvslog] arm: get_cabac inline asm
Janne Grunau
git at videolan.org
Sun Mar 9 14:26:45 CET 2014
ffmpeg | branch: master | Janne Grunau <janne-libav at jannau.net> | Wed Jan 29 14:48:22 2014 +0100| [634d9d8b398982647b3d7160641198744901d8d8] | committer: Janne Grunau
arm: get_cabac inline asm
Based on the aarch64 asm. CPU cycle counts on cortex-a9 compared to
gcc 4.8.2:
before: 475 decicycles in get_cabac_noinline, 67106035 runs, 2829 skips
after: 393 decicycles in get_cabac_noinline, 67106474 runs, 2390 skips
Overall speedup is above 2%. Code generated by clang 3.4 is slower on
the same hardware and the relative change is a little larger.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=634d9d8b398982647b3d7160641198744901d8d8
---
libavcodec/arm/cabac.h | 102 ++++++++++++++++++++++++++++++++++++++++++
libavcodec/cabac_functions.h | 3 ++
2 files changed, 105 insertions(+)
diff --git a/libavcodec/arm/cabac.h b/libavcodec/arm/cabac.h
new file mode 100644
index 0000000..6ff5f1a
--- /dev/null
+++ b/libavcodec/arm/cabac.h
@@ -0,0 +1,102 @@
+/*
+ * 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 AVCODEC_ARM_CABAC_H
+#define AVCODEC_ARM_CABAC_H
+
+#include "config.h"
+#if HAVE_ARMV6T2_INLINE
+
+#include "libavutil/attributes.h"
+#include "libavutil/internal.h"
+#include "libavcodec/cabac.h"
+
+#define get_cabac_inline get_cabac_inline_arm
+static av_always_inline int get_cabac_inline_arm(CABACContext *c,
+ uint8_t *const state)
+{
+ int bit;
+ void *reg_b, *reg_c, *tmp;
+
+ __asm__ volatile(
+ "ldrb %[bit] , [%[state]] \n\t"
+ "add %[r_b] , %[tables] , %[lps_off] \n\t"
+ "mov %[tmp] , %[range] \n\t"
+ "and %[range] , %[range] , #0xC0 \n\t"
+ "add %[r_b] , %[r_b] , %[bit] \n\t"
+ "ldrb %[range] , [%[r_b], %[range], lsl #1] \n\t"
+ "add %[r_b] , %[tables] , %[norm_off] \n\t"
+ "sub %[r_c] , %[tmp] , %[range] \n\t"
+ "lsl %[tmp] , %[r_c] , #17 \n\t"
+ "cmp %[tmp] , %[low] \n\t"
+ "it gt \n\t"
+ "movgt %[range] , %[r_c] \n\t"
+ "itt cc \n\t"
+ "mvncc %[bit] , %[bit] \n\t"
+ "subcc %[low] , %[low] , %[tmp] \n\t"
+ "add %[r_c] , %[tables] , %[mlps_off] \n\t"
+ "ldrb %[tmp] , [%[r_b], %[range]] \n\t"
+ "ldrb %[r_b] , [%[r_c], %[bit]] \n\t"
+ "lsl %[low] , %[low] , %[tmp] \n\t"
+ "lsl %[range] , %[range] , %[tmp] \n\t"
+ "uxth %[r_c] , %[low] \n\t"
+ "strb %[r_b] , [%[state]] \n\t"
+ "tst %[r_c] , %[r_c] \n\t"
+ "bne 2f \n\t"
+ "ldr %[r_c] , [%[c], %[byte]] \n\t"
+ "ldr %[r_b] , [%[c], %[end]] \n\t"
+ "ldrh %[tmp] , [%[r_c]] \n\t"
+ "cmp %[r_c] , %[r_b] \n\t"
+ "itt lt \n\t"
+ "addlt %[r_c] , %[r_c] , #2 \n\t"
+ "strlt %[r_c] , [%[c], %[byte]] \n\t"
+ "sub %[r_c] , %[low] , #1 \n\t"
+ "add %[r_b] , %[tables] , %[norm_off] \n\t"
+ "eor %[r_c] , %[low] , %[r_c] \n\t"
+ "rev %[tmp] , %[tmp] \n\t"
+ "lsr %[r_c] , %[r_c] , #15 \n\t"
+ "lsr %[tmp] , %[tmp] , #15 \n\t"
+ "ldrb %[r_c] , [%[r_b], %[r_c]] \n\t"
+ "movw %[r_b] , #0xFFFF \n\t"
+ "sub %[tmp] , %[tmp] , %[r_b] \n\t"
+ "rsb %[r_c] , %[r_c] , #7 \n\t"
+ "lsl %[tmp] , %[tmp] , %[r_c] \n\t"
+ "add %[low] , %[low] , %[tmp] \n\t"
+ "2: \n\t"
+ : [bit]"=&r"(bit),
+ [low]"+&r"(c->low),
+ [range]"+&r"(c->range),
+ [r_b]"=&r"(reg_b),
+ [r_c]"=&r"(reg_c),
+ [tmp]"=&r"(tmp)
+ : [c]"r"(c),
+ [state]"r"(state),
+ [tables]"r"(ff_h264_cabac_tables),
+ [byte]"M"(offsetof(CABACContext, bytestream)),
+ [end]"M"(offsetof(CABACContext, bytestream_end)),
+ [norm_off]"I"(H264_NORM_SHIFT_OFFSET),
+ [lps_off]"I"(H264_LPS_RANGE_OFFSET),
+ [mlps_off]"I"(H264_MLPS_STATE_OFFSET + 128)
+ : "memory", "cc"
+ );
+
+ return bit & 1;
+}
+#endif /* HAVE_ARMV6T2_INLINE */
+
+#endif /* AVCODEC_ARM_CABAC_H */
diff --git a/libavcodec/cabac_functions.h b/libavcodec/cabac_functions.h
index 39f0afb..4b8f1bc 100644
--- a/libavcodec/cabac_functions.h
+++ b/libavcodec/cabac_functions.h
@@ -35,6 +35,9 @@
#if ARCH_AARCH64
# include "aarch64/cabac.h"
#endif
+#if ARCH_ARM
+# include "arm/cabac.h"
+#endif
#if ARCH_X86
# include "x86/cabac.h"
#endif
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