From 378d1b06c350e09ac604566130b39126fd858478 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?R=C3=A9mi=20Denis-Courmont?= Date: Sat, 8 Jun 2024 10:57:15 +0300 Subject: [PATCH] riscv: probe for Zbb extension at load time Due to hysterical raisins, most RISC-V Linux distributions target a RV64GC baseline excluding the Bit-manipulation ISA extensions, most notably: - Zba: address generation extension and - Zbb: basic bit manipulation extension. Most CPUs that would make sense to run FFmpeg on support Zba and Zbb (including the current FATE runner), so it makes sense to optimise for them. In fact a large chunk of existing assembler optimisations relies on Zba and/or Zbb. Since we cannot patch shared library code, the next best thing is to carry a flag initialised at load-time and check it on need basis. This results in 3 instructions overhead on isolated use, e.g.: 1: AUIPC rd, %pcrel_hi(ff_rv_zbb_supported) LBU rd, %pcrel_lo(1b)(rd) BEQZ rd, non_Zbb_fallback_code // Zbb code here The C compiler will typically load the flag ahead of time to reducing latency, and can also keep it around if Zbb is used multiple times in a single optimisation scope. For this to work, the flag symbol must be hidden; otherwise the optimisation degrades with a GOT look-up to support interposition: 1: AUIPC rd, GOT_OFFSET_HI LD rd, GOT_OFFSET_LO(rd) LBU rd, (rd) BEQZ rd, non_Zbb_fallback_code // Zbb code here This patch adds code to provision the flag in libraries using bit manipulation functions from libavutil: byte-swap, bit-weight and counting leading or trailing zeroes. --- libavcodec/riscv/Makefile | 2 ++ libavcodec/riscv/cpu_common.c | 1 + libavdevice/riscv/Makefile | 1 + libavdevice/riscv/cpu_common.c | 1 + libavfilter/riscv/Makefile | 2 ++ libavfilter/riscv/cpu_common.c | 1 + libavformat/riscv/Makefile | 1 + libavformat/riscv/cpu_common.c | 1 + libavutil/riscv/Makefile | 3 ++- libavutil/riscv/cpu.h | 14 ++++++++++++++ libavutil/riscv/cpu_common.c | 33 +++++++++++++++++++++++++++++++++ libswscale/riscv/Makefile | 2 ++ libswscale/riscv/cpu_common.c | 1 + tests/ref/fate/source | 5 +++++ 14 files changed, 67 insertions(+), 1 deletion(-) create mode 100644 libavcodec/riscv/cpu_common.c create mode 100644 libavdevice/riscv/Makefile create mode 100644 libavdevice/riscv/cpu_common.c create mode 100644 libavfilter/riscv/cpu_common.c create mode 100644 libavformat/riscv/Makefile create mode 100644 libavformat/riscv/cpu_common.c create mode 100644 libavutil/riscv/cpu_common.c create mode 100644 libswscale/riscv/cpu_common.c diff --git a/libavcodec/riscv/Makefile b/libavcodec/riscv/Makefile index 590655f829..c180223141 100644 --- a/libavcodec/riscv/Makefile +++ b/libavcodec/riscv/Makefile @@ -77,3 +77,5 @@ RVV-OBJS-$(CONFIG_VP9_DECODER) += riscv/vp9_intra_rvv.o \ riscv/vp9_mc_rvv.o OBJS-$(CONFIG_VORBIS_DECODER) += riscv/vorbisdsp_init.o RVV-OBJS-$(CONFIG_VORBIS_DECODER) += riscv/vorbisdsp_rvv.o + +SHLIBOBJS += riscv/cpu_common.o diff --git a/libavcodec/riscv/cpu_common.c b/libavcodec/riscv/cpu_common.c new file mode 100644 index 0000000000..17c9b392c9 --- /dev/null +++ b/libavcodec/riscv/cpu_common.c @@ -0,0 +1 @@ +#include "libavutil/riscv/cpu_common.c" diff --git a/libavdevice/riscv/Makefile b/libavdevice/riscv/Makefile new file mode 100644 index 0000000000..52857aacba --- /dev/null +++ b/libavdevice/riscv/Makefile @@ -0,0 +1 @@ +SHLIBOBJS += riscv/cpu_common.o diff --git a/libavdevice/riscv/cpu_common.c b/libavdevice/riscv/cpu_common.c new file mode 100644 index 0000000000..17c9b392c9 --- /dev/null +++ b/libavdevice/riscv/cpu_common.c @@ -0,0 +1 @@ +#include "libavutil/riscv/cpu_common.c" diff --git a/libavfilter/riscv/Makefile b/libavfilter/riscv/Makefile index 277dde2aed..14a4470d96 100644 --- a/libavfilter/riscv/Makefile +++ b/libavfilter/riscv/Makefile @@ -1,2 +1,4 @@ OBJS-$(CONFIG_AFIR_FILTER) += riscv/af_afir_init.o RVV-OBJS-$(CONFIG_AFIR_FILTER) += riscv/af_afir_rvv.o + +SHLIBOBJS += riscv/cpu_common.o diff --git a/libavfilter/riscv/cpu_common.c b/libavfilter/riscv/cpu_common.c new file mode 100644 index 0000000000..17c9b392c9 --- /dev/null +++ b/libavfilter/riscv/cpu_common.c @@ -0,0 +1 @@ +#include "libavutil/riscv/cpu_common.c" diff --git a/libavformat/riscv/Makefile b/libavformat/riscv/Makefile new file mode 100644 index 0000000000..52857aacba --- /dev/null +++ b/libavformat/riscv/Makefile @@ -0,0 +1 @@ +SHLIBOBJS += riscv/cpu_common.o diff --git a/libavformat/riscv/cpu_common.c b/libavformat/riscv/cpu_common.c new file mode 100644 index 0000000000..17c9b392c9 --- /dev/null +++ b/libavformat/riscv/cpu_common.c @@ -0,0 +1 @@ +#include "libavutil/riscv/cpu_common.c" diff --git a/libavutil/riscv/Makefile b/libavutil/riscv/Makefile index 7e9a51194b..5db4c432d9 100644 --- a/libavutil/riscv/Makefile +++ b/libavutil/riscv/Makefile @@ -1,7 +1,8 @@ OBJS += riscv/float_dsp_init.o \ riscv/fixed_dsp_init.o \ riscv/lls_init.o \ - riscv/cpu.o + riscv/cpu.o \ + riscv/cpu_common.o RVV-OBJS += riscv/float_dsp_rvv.o \ riscv/fixed_dsp_rvv.o \ riscv/lls_rvv.o diff --git a/libavutil/riscv/cpu.h b/libavutil/riscv/cpu.h index af1440f626..bb8e08aa14 100644 --- a/libavutil/riscv/cpu.h +++ b/libavutil/riscv/cpu.h @@ -24,8 +24,22 @@ #include "config.h" #include #include +#include "libavutil/attributes_internal.h" #include "libavutil/cpu.h" +#ifndef __riscv_zbb +extern attribute_visibility_hidden bool ff_rv_zbb_supported; +#endif + +static inline av_const bool ff_rv_zbb_support(void) +{ +#ifndef __riscv_zbb + return ff_rv_zbb_supported; +#else + return true; +#endif +} + #if HAVE_RVV /** * Returns the vector size in bytes (always a power of two and at least 4). diff --git a/libavutil/riscv/cpu_common.c b/libavutil/riscv/cpu_common.c new file mode 100644 index 0000000000..3ecf95809b --- /dev/null +++ b/libavutil/riscv/cpu_common.c @@ -0,0 +1,33 @@ +/* + * Copyright © 2024 Rémi Denis-Courmont. + * + * 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/cpu.h" + +#ifndef __riscv_zbb +unsigned char ff_rv_zbb_supported = 0; + +#ifdef __ELF__ +__attribute__((constructor)) +static void probe_zbb(void) +{ + ff_rv_zbb_supported = (av_get_cpu_flags() & AV_CPU_FLAG_RVB_BASIC) != 0; +} +#endif +#endif diff --git a/libswscale/riscv/Makefile b/libswscale/riscv/Makefile index 6038c8d873..7c8977d940 100644 --- a/libswscale/riscv/Makefile +++ b/libswscale/riscv/Makefile @@ -4,3 +4,5 @@ RV-OBJS += riscv/rgb2rgb_rvb.o RVV-OBJS += riscv/input_rvv.o \ riscv/range_rvv.o \ riscv/rgb2rgb_rvv.o + +SHLIBOBJS += riscv/cpu_common.o diff --git a/libswscale/riscv/cpu_common.c b/libswscale/riscv/cpu_common.c new file mode 100644 index 0000000000..17c9b392c9 --- /dev/null +++ b/libswscale/riscv/cpu_common.c @@ -0,0 +1 @@ +#include "libavutil/riscv/cpu_common.c" diff --git a/tests/ref/fate/source b/tests/ref/fate/source index d7b48a8b85..1703b36c02 100644 --- a/tests/ref/fate/source +++ b/tests/ref/fate/source @@ -3,16 +3,21 @@ libavcodec/file_open.c libavcodec/interplayacm.c libavcodec/log2_tab.c libavcodec/reverse.c +libavcodec/riscv/cpu_common.c libavdevice/file_open.c libavdevice/reverse.c +libavdevice/riscv/cpu_common.c libavfilter/file_open.c libavfilter/log2_tab.c +libavfilter/riscv/cpu_common.c libavformat/file_open.c libavformat/golomb_tab.c libavformat/log2_tab.c libavformat/rangecoder_dec.c +libavformat/riscv/cpu_common.c libswresample/log2_tab.c libswscale/log2_tab.c +libswscale/riscv/cpu_common.c tools/uncoded_frame.c tools/yuvcmp.c Headers without standard inclusion guards: