[FFmpeg-cvslog] aarch64: get_cabac inline asm
Janne Grunau
git at videolan.org
Sun Mar 9 13:37:25 CET 2014
ffmpeg | branch: master | Janne Grunau <janne-libav at jannau.net> | Mon Jan 13 01:06:20 2014 +0100| [dfe224f377be3e45758c69d881ca7874b82d647a] | committer: Janne Grunau
aarch64: get_cabac inline asm
Based on the x86 branchless get_cabac asm. get_cabac_noinline() gets
approximately 20% faster (no cycle counts available) compared to clang
from Xcode 5.1 beta5. More than 6% faster overall. A part of the overall
speedup might be explained by additional inlining of get_cabac().
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=dfe224f377be3e45758c69d881ca7874b82d647a
---
libavcodec/aarch64/cabac.h | 104 ++++++++++++++++++++++++++++++++++++++++++
libavcodec/cabac.h | 1 +
libavcodec/cabac_functions.h | 4 +-
3 files changed, 108 insertions(+), 1 deletion(-)
diff --git a/libavcodec/aarch64/cabac.h b/libavcodec/aarch64/cabac.h
new file mode 100644
index 0000000..e12953e
--- /dev/null
+++ b/libavcodec/aarch64/cabac.h
@@ -0,0 +1,104 @@
+/*
+ * 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_AARCH64_CABAC_H
+#define AVCODEC_AARCH64_CABAC_H
+
+#include "config.h"
+#if HAVE_INLINE_ASM
+
+#include "libavutil/attributes.h"
+#include "libavutil/internal.h"
+#include "libavcodec/cabac.h"
+
+#define get_cabac_inline get_cabac_inline_aarch64
+static av_always_inline int get_cabac_inline_aarch64(CABACContext *c,
+ uint8_t *const state)
+{
+ int bit;
+ void *reg_a, *reg_b, *reg_c, *tmp;
+
+ __asm__ volatile(
+ "ldrb %w[bit] , [%[state]] \n\t"
+ "add %[r_b] , %[tables] , %[lps_off] \n\t"
+ "mov %w[tmp] , %w[range] \n\t"
+ "and %w[range] , %w[range] , #0xC0 \n\t"
+ "lsl %w[r_c] , %w[range] , #1 \n\t"
+ "add %[r_b] , %[r_b] , %w[bit], UXTW \n\t"
+ "ldrb %w[range] , [%[r_b], %w[r_c], SXTW] \n\t"
+ "sub %w[r_c] , %w[tmp] , %w[range] \n\t"
+ "lsl %w[tmp] , %w[r_c] , #17 \n\t"
+ "cmp %w[tmp] , %w[low] \n\t"
+ "csel %w[tmp] , %w[tmp] , wzr , cc \n\t"
+ "csel %w[range] , %w[r_c] , %w[range], gt \n\t"
+ "cinv %w[bit] , %w[bit] , cc \n\t"
+ "sub %w[low] , %w[low] , %w[tmp] \n\t"
+ "add %[r_b] , %[tables] , %[norm_off] \n\t"
+ "add %[r_a] , %[tables] , %[mlps_off] \n\t"
+ "ldrb %w[tmp] , [%[r_b], %w[range], SXTW] \n\t"
+ "ldrb %w[r_a] , [%[r_a], %w[bit], SXTW] \n\t"
+ "lsl %w[low] , %w[low] , %w[tmp] \n\t"
+ "lsl %w[range] , %w[range] , %w[tmp] \n\t"
+ "uxth %w[r_c] , %w[low] \n\t"
+ "strb %w[r_a] , [%[state]] \n\t"
+ "cbnz %w[r_c] , 2f \n\t"
+ "ldr %[r_c] , [%[c], %[byte]] \n\t"
+ "ldr %[r_a] , [%[c], %[end]] \n\t"
+ "ldrh %w[tmp] , [%[r_c]] \n\t"
+ "cmp %[r_c] , %[r_a] \n\t"
+ "b.ge 1f \n\t"
+ "add %[r_a] , %[r_c] , #2 \n\t"
+ "str %[r_a] , [%[c], %[byte]] \n\t"
+ "1: \n\t"
+ "sub %w[r_c] , %w[low] , #1 \n\t"
+ "eor %w[r_c] , %w[r_c] , %w[low] \n\t"
+ "rev %w[tmp] , %w[tmp] \n\t"
+ "lsr %w[r_c] , %w[r_c] , #15 \n\t"
+ "lsr %w[tmp] , %w[tmp] , #15 \n\t"
+ "ldrb %w[r_c] , [%[r_b], %w[r_c], SXTW] \n\t"
+ "mov %w[r_b] , #0xFFFF \n\t"
+ "mov %w[r_a] , #7 \n\t"
+ "sub %w[tmp] , %w[tmp] , %w[r_b] \n\t"
+ "sub %w[r_c] , %w[r_a] , %w[r_c] \n\t"
+ "lsl %w[tmp] , %w[tmp] , %w[r_c] \n\t"
+ "add %w[low] , %w[low] , %w[tmp] \n\t"
+ "2: \n\t"
+ : [bit]"=&r"(bit),
+ [low]"+&r"(c->low),
+ [range]"+&r"(c->range),
+ [r_a]"=&r"(reg_a),
+ [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]"i"(offsetof(CABACContext, bytestream)),
+ [end]"i"(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_INLINE_ASM */
+
+#endif /* AVCODEC_AARCH64_CABAC_H */
diff --git a/libavcodec/cabac.h b/libavcodec/cabac.h
index 7401bc9..426f338 100644
--- a/libavcodec/cabac.h
+++ b/libavcodec/cabac.h
@@ -31,6 +31,7 @@
#include "put_bits.h"
+extern uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63];
#define H264_NORM_SHIFT_OFFSET 0
#define H264_LPS_RANGE_OFFSET 512
#define H264_MLPS_STATE_OFFSET 1024
diff --git a/libavcodec/cabac_functions.h b/libavcodec/cabac_functions.h
index 11c9646..39f0afb 100644
--- a/libavcodec/cabac_functions.h
+++ b/libavcodec/cabac_functions.h
@@ -32,11 +32,13 @@
#include "cabac.h"
#include "config.h"
+#if ARCH_AARCH64
+# include "aarch64/cabac.h"
+#endif
#if ARCH_X86
# include "x86/cabac.h"
#endif
-extern uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63];
static uint8_t * const ff_h264_norm_shift = ff_h264_cabac_tables + H264_NORM_SHIFT_OFFSET;
static uint8_t * const ff_h264_lps_range = ff_h264_cabac_tables + H264_LPS_RANGE_OFFSET;
static uint8_t * const ff_h264_mlps_state = ff_h264_cabac_tables + H264_MLPS_STATE_OFFSET;
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