[FFmpeg-devel] [PATCH 1/2] configure: check if assembler supports RV zicbop

[FFmpeg-devel] [PATCH 1/2] configure: check if assembler supports RV zicbop

[Rémi Denis-Courmont]

zicbop is the Cache Block Operation, Prefetch extension to RVI.
---
 configure | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure b/configure
index f6f5c29fea..40774e1a88 100755
--- a/configure
+++ b/configure
@@ -2218,6 +2218,7 @@ ARCH_EXT_LIST_PPC="
 ARCH_EXT_LIST_RISCV="
     rv
     rvv
+    rv_zicbop
     rv_zvbb
 "
 
@@ -2763,6 +2764,7 @@ power8_deps="vsx"
 
 rv_deps="riscv"
 rvv_deps="rv"
+rv_zicbop="riscv"
 rv_zvbb_deps="rvv"
 
 loongson2_deps="mips"
@@ -6365,6 +6367,7 @@ elif enabled riscv; then
 
     enabled rv && check_inline_asm rv '".option arch, +zbb\nrev8 t0, t1"'
     enabled rvv && check_inline_asm rvv '".option arch, +v\nvsetivli zero, 0, e8, m1, ta, ma"'
+    enabled rv_zicbop && check_inline_asm rv_zicbop '".option arch, +zicbop\nprefetch.r 64(a0)"'
     enabled rv_zvbb && check_inline_asm rv_zvbb '".option arch, +zvbb\nvclz.v v0, v8"'
 
 elif enabled x86; then
@@ -7921,6 +7924,7 @@ if enabled loongarch; then
     echo "LASX enabled              ${lasx-no}"
 fi
 if enabled riscv; then
+    echo "RISC-V CBO Prefetch       ${rv_zicbop-no}"
     echo "RISC-V Vector enabled     ${rvv-no}"
 fi
 echo "debug symbols             ${debug-no}"
-- 
2.45.2

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[FFmpeg-devel] [PATCH 2/2] lavc/videodsp: RISC-V zicbop prefetch

[Rémi Denis-Courmont]

There are currently no ways to run-time detect the CPU capability, so we
take it for granted (in the worst case, it will execute NOPs).
---
 libavcodec/riscv/Makefile        |  2 ++
 libavcodec/riscv/videodsp.S      | 34 ++++++++++++++++++++++++++++++
 libavcodec/riscv/videodsp_init.c | 36 ++++++++++++++++++++++++++++++++
 libavcodec/videodsp.c            |  2 ++
 libavcodec/videodsp.h            |  1 +
 5 files changed, 75 insertions(+)
 create mode 100644 libavcodec/riscv/videodsp.S
 create mode 100644 libavcodec/riscv/videodsp_init.c

diff --git a/libavcodec/riscv/Makefile b/libavcodec/riscv/Makefile
index 0bbdd38116..05d0646256 100644
--- a/libavcodec/riscv/Makefile
+++ b/libavcodec/riscv/Makefile
@@ -67,6 +67,8 @@ RVV-OBJS-$(CONFIG_UTVIDEO_DECODER) += riscv/utvideodsp_rvv.o
 OBJS-$(CONFIG_VC1DSP) += riscv/vc1dsp_init.o
 RV-OBJS-$(CONFIG_VC1DSP) += riscv/vc1dsp_rvi.o
 RVV-OBJS-$(CONFIG_VC1DSP) += riscv/vc1dsp_rvv.o
+OBJS-$(CONFIG_VIDEODSP) += riscv/videodsp_init.o
+RV-OBJS-$(CONFIG_VIDEODSP) += riscv/videodsp.o
 OBJS-$(CONFIG_VP7_DECODER) += riscv/vp7dsp_init.o
 RVV-OBJS-$(CONFIG_VP7_DECODER) += riscv/vp7dsp_rvv.o
 OBJS-$(CONFIG_VP8DSP) += riscv/vp8dsp_init.o
diff --git a/libavcodec/riscv/videodsp.S b/libavcodec/riscv/videodsp.S
new file mode 100644
index 0000000000..72bf70ec52
--- /dev/null
+++ b/libavcodec/riscv/videodsp.S
@@ -0,0 +1,34 @@
+/*
+ * Copyright © 2022 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 "config.h"
+#include "libavutil/riscv/asm.S"
+
+#if HAVE_RV_ZICBOP
+func ff_prefetch_rv_zicbop, zicbop
+1:
+        addi    a2, a2, -1
+        prefetch.r  (a0)
+        add     a0, a0, a1
+        bnez    a2, 1b
+
+        ret
+endfunc
+#endif
diff --git a/libavcodec/riscv/videodsp_init.c b/libavcodec/riscv/videodsp_init.c
new file mode 100644
index 0000000000..f2c9aae3ca
--- /dev/null
+++ b/libavcodec/riscv/videodsp_init.c
@@ -0,0 +1,36 @@
+/*
+ * 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 "config.h"
+#include "libavutil/attributes.h"
+#include "libavutil/cpu.h"
+#include "libavcodec/videodsp.h"
+
+void ff_prefetch_rv_zicbop(const uint8_t *mem, ptrdiff_t stride, int h);
+
+av_cold void ff_videodsp_init_riscv(VideoDSPContext *ctx, int bpc)
+{
+#if HAVE_RV_ZICBOP
+    /* TODO: Since we pay for the indirect function call anyway, we should
+     * only set this if Cache-Block Operation Prefetch (Zicbop) is actually
+     * supported and otherwise save a few cycles of NOPs.
+     * But so far there are no means to detect Zicbop (in user mode).
+     */
+    ctx->prefetch = ff_prefetch_rv_zicbop;
+#endif
+}
diff --git a/libavcodec/videodsp.c b/libavcodec/videodsp.c
index bdff2e76f5..a19e87a819 100644
--- a/libavcodec/videodsp.c
+++ b/libavcodec/videodsp.c
@@ -51,6 +51,8 @@ av_cold void ff_videodsp_init(VideoDSPContext *ctx, int bpc)
     ff_videodsp_init_arm(ctx, bpc);
 #elif ARCH_PPC
     ff_videodsp_init_ppc(ctx, bpc);
+#elif ARCH_RISCV
+    ff_videodsp_init_riscv(ctx, bpc);
 #elif ARCH_X86
     ff_videodsp_init_x86(ctx, bpc);
 #elif ARCH_MIPS
diff --git a/libavcodec/videodsp.h b/libavcodec/videodsp.h
index e8960b609d..1be3188d09 100644
--- a/libavcodec/videodsp.h
+++ b/libavcodec/videodsp.h
@@ -81,6 +81,7 @@ void ff_videodsp_init(VideoDSPContext *ctx, int bpc);
 void ff_videodsp_init_aarch64(VideoDSPContext *ctx, int bpc);
 void ff_videodsp_init_arm(VideoDSPContext *ctx, int bpc);
 void ff_videodsp_init_ppc(VideoDSPContext *ctx, int bpc);
+void ff_videodsp_init_riscv(VideoDSPContext *ctx, int bpc);
 void ff_videodsp_init_x86(VideoDSPContext *ctx, int bpc);
 void ff_videodsp_init_mips(VideoDSPContext *ctx, int bpc);
 void ff_videodsp_init_loongarch(VideoDSPContext *ctx, int bpc);
-- 
2.45.2

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