af_afir: RISC-V V fcmul_add

Segmented loads are slow, so here we use unit-strided load and narrowing shifts.

c910:
fcmul_add_c: 2179
fcmul_add_rvv_f64: 1652

c908:
fcmul_add_c: 4891.2
fcmul_add_rvv_f64: 2399.5
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

libavfilter/af_afirdsp.h

@@ -33,6 +33,7 @@ typedef struct AudioFIRDSPContext {
                       ptrdiff_t len);
 } AudioFIRDSPContext;
 
+void ff_afir_init_riscv(AudioFIRDSPContext *s);
 void ff_afir_init_x86(AudioFIRDSPContext *s);
 
 static void fcmul_add_c(float *sum, const float *t, const float *c, ptrdiff_t len)
@@ -74,7 +75,9 @@ static av_unused void ff_afir_init(AudioFIRDSPContext *dsp)
     dsp->fcmul_add = fcmul_add_c;
     dsp->dcmul_add = dcmul_add_c;
 
-#if ARCH_X86
+#if ARCH_RISCV
+    ff_afir_init_riscv(dsp);
+#elif ARCH_X86
     ff_afir_init_x86(dsp);
 #endif
 }

libavfilter/riscv/Makefile

+OBJS += riscv/af_afir_init.o
+RVV-OBJS += riscv/af_afir_rvv.o

libavfilter/riscv/af_afir_init.c

+/*
+ * Copyright (c) 2023 Institue of Software Chinese Academy of Sciences (ISCAS).
+ *
+ * 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 "config.h"
+#include "libavutil/attributes.h"
+#include "libavutil/cpu.h"
+#include "libavfilter/af_afirdsp.h"
+
+void ff_fcmul_add_rvv(float *sum, const float *t, const float *c,
+                       ptrdiff_t len);
+
+av_cold void ff_afir_init_riscv(AudioFIRDSPContext *s)
+{
+#if HAVE_RVV
+    int flags = av_get_cpu_flags();
+
+    if (flags & AV_CPU_FLAG_RVV_F64) {
+        if (flags & AV_CPU_FLAG_RVB_ADDR) {
+            s->fcmul_add = ff_fcmul_add_rvv;
+        }
+    }
+#endif
+}

libavfilter/riscv/af_afir_rvv.S

+/*
+ * Copyright (c) 2023 Institue of Software Chinese Academy of Sciences (ISCAS).
+ *
+ * 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"
+
+//  void ff_fcmul_add(float *sum, const float *t, const float *c, int len)
+func ff_fcmul_add_rvv, zve64f
+        li          t1, 32
+1:
+        vsetvli     t0, a3, e32, m4, ta, ma
+        vle64.v     v24, (a0)
+        sub         a3, a3, t0
+        vnsrl.wx    v16, v24, zero
+        vnsrl.wx    v20, v24, t1
+        vle64.v     v24, (a1)
+        sh3add      a1, t0, a1
+        vnsrl.wx    v0, v24, zero
+        vnsrl.wx    v4, v24, t1
+        vle64.v     v24, (a2)
+        sh3add      a2, t0, a2
+        vnsrl.wx    v8, v24, zero
+        vnsrl.wx    v12, v24, t1
+        vfmacc.vv   v16, v0, v8
+        vfmacc.vv   v20, v4, v8
+        vfnmsac.vv  v16, v4, v12
+        vfmacc.vv   v20, v0, v12
+        vsseg2e32.v v16, (a0)
+        sh3add      a0, t0, a0
+        bgtz        a3, 1b
+
+        flw         fa0, 0(a1)
+        flw         fa1, 0(a2)
+        flw         fa2, 0(a0)
+        fmadd.s     fa2, fa0, fa1, fa2
+        fsw         fa2, 0(a0)
+
+        ret
+endfunc