[FFmpeg-devel] [PATCH 1/6] lavc/ac3dsp: RISC-V V ac3_exponent_min

[Peiting Shen <shenpeiting@eswincomputing.com>]

From: Shen Peiting <shenpeiting@eswincomputing.com>

Find scalar minium optimized by using RVV instructions

Benchmarks on Spike(cycles):
*exp=1280*4;num_reuse_blocks=5;nb_coefs=16
ac3_exponent_min_c: 1993
ac3_exponent_min_rvv: 258
*exp=1280*4;num_reuse_blocks=19;nb_coefs=255
ac3_exponent_min_c: 99010
ac3_exponent_min_rvv: 3843

The optimization performance is more obvious with the increase of number of
reuse blocks and number of coefs.

Co-Authored by: Yang Xiaojun <yangxiaojun@eswincomputing.com>
Co-Authored by: Huang Xing <huangxing1@eswincomputing.com>
Co-Authored by: Zeng Fanchen <zengfanchen@eswincomputing.com>
Signed-off-by: Shen Peiting <shenpeiting@eswincomputing.com>
---
 libavcodec/ac3dsp.c            |  2 ++
 libavcodec/ac3dsp.h            |  1 +
 libavcodec/riscv/Makefile      |  2 ++
 libavcodec/riscv/ac3dsp_init.c | 37 +++++++++++++++++++++++++++
 libavcodec/riscv/ac3dsp_rvv.S  | 46 ++++++++++++++++++++++++++++++++++
 5 files changed, 88 insertions(+)
 create mode 100644 libavcodec/riscv/ac3dsp_init.c
 create mode 100644 libavcodec/riscv/ac3dsp_rvv.S

diff --git a/libavcodec/ac3dsp.c b/libavcodec/ac3dsp.c
index 22cb5f242e..302b786b15 100644
--- a/libavcodec/ac3dsp.c
+++ b/libavcodec/ac3dsp.c
@@ -395,5 +395,7 @@ av_cold void ff_ac3dsp_init(AC3DSPContext *c)
     ff_ac3dsp_init_x86(c);
 #elif ARCH_MIPS
     ff_ac3dsp_init_mips(c);
+#elif ARCH_RISCV
+    ff_ac3dsp_init_riscv(c);
 #endif
 }
diff --git a/libavcodec/ac3dsp.h b/libavcodec/ac3dsp.h
index 33e51e202e..a01bff3d11 100644
--- a/libavcodec/ac3dsp.h
+++ b/libavcodec/ac3dsp.h
@@ -109,6 +109,7 @@ void ff_ac3dsp_init    (AC3DSPContext *c);
 void ff_ac3dsp_init_arm(AC3DSPContext *c);
 void ff_ac3dsp_init_x86(AC3DSPContext *c);
 void ff_ac3dsp_init_mips(AC3DSPContext *c);
+void ff_ac3dsp_init_riscv(AC3DSPContext *c);
 
 void ff_ac3dsp_downmix(AC3DSPContext *c, float **samples, float **matrix,
                        int out_ch, int in_ch, int len);
diff --git a/libavcodec/riscv/Makefile b/libavcodec/riscv/Makefile
index ee17a521fd..a627924cac 100644
--- a/libavcodec/riscv/Makefile
+++ b/libavcodec/riscv/Makefile
@@ -1,5 +1,7 @@
 OBJS-$(CONFIG_AAC_DECODER) += riscv/aacpsdsp_init.o
 RVV-OBJS-$(CONFIG_AAC_DECODER) += riscv/aacpsdsp_rvv.o
+OBJS-$(CONFIG_AC3DSP) += riscv/ac3dsp_init.o
+RVV-OBJS-$(CONFIG_AC3DSP) += riscv/ac3dsp_rvv.o
 OBJS-$(CONFIG_ALAC_DECODER) += riscv/alacdsp_init.o
 RVV-OBJS-$(CONFIG_ALAC_DECODER) += riscv/alacdsp_rvv.o
 OBJS-$(CONFIG_AUDIODSP) += riscv/audiodsp_init.o \
diff --git a/libavcodec/riscv/ac3dsp_init.c b/libavcodec/riscv/ac3dsp_init.c
new file mode 100644
index 0000000000..bb67d86998
--- /dev/null
+++ b/libavcodec/riscv/ac3dsp_init.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright 2023 Beijing ESWIN Computing Technology Co., Ltd.
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <stdint.h>
+
+#include "libavutil/attributes.h"
+#include "libavcodec/ac3dsp.h"
+#include "libavutil/cpu.h"
+#include "config.h"
+
+void ff_ac3_exponent_min_rvv(uint8_t *exp, int num_reuse_blocks, int nb_coefs);
+
+av_cold void ff_ac3dsp_init_riscv(AC3DSPContext *c)
+{
+    int flags = av_get_cpu_flags();
+#if HAVE_RVV
+    if (flags & AV_CPU_FLAG_RVV_I32)
+        c->ac3_exponent_min = ff_ac3_exponent_min_rvv;
+#endif
+}
+
diff --git a/libavcodec/riscv/ac3dsp_rvv.S b/libavcodec/riscv/ac3dsp_rvv.S
new file mode 100644
index 0000000000..879123f4a7
--- /dev/null
+++ b/libavcodec/riscv/ac3dsp_rvv.S
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2023 Beijing ESWIN Computing Technology Co., Ltd.
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/riscv/asm.S"
+
+func ff_ac3_exponent_min_rvv, zve32x
+    beq             a1, x0, 3f
+    li              t0, 256
+    addi            a1, a1, 1
+1:
+    mv              t2, a0
+    mv              t3, a1
+    lb              t4, (t2)
+2:
+    vsetvli         t1, t3, e8, m8
+    vlse8.v         v0, (t2), t0
+    vmv.s.x         v8, t4
+    sub             t3, t3, t1
+    vredminu.vs     v8, v0, v8
+    vmv.x.s         t4, v8
+    bnez            t3, 2b
+    vsetivli        t1, 1, e8
+    vse8.v          v8, (a0)
+    addi            a0, a0, 1
+    addi            a2, a2, -1
+    bnez            a2, 1b
+3:
+    ret
+endfunc
-- 
2.17.1

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