lavu/floatdsp: RISC-V V vector_fmul_scalar

This is based on existing code from the VLC git tree with two minor
changes to account for the different function prototypes.

libavutil/float_dsp.c

@@ -156,6 +156,8 @@ av_cold AVFloatDSPContext *avpriv_float_dsp_alloc(int bit_exact)
     ff_float_dsp_init_arm(fdsp);
 #elif ARCH_PPC
     ff_float_dsp_init_ppc(fdsp, bit_exact);
+#elif ARCH_RISCV
+    ff_float_dsp_init_riscv(fdsp);
 #elif ARCH_X86
     ff_float_dsp_init_x86(fdsp);
 #elif ARCH_MIPS

libavutil/float_dsp.h

@@ -205,6 +205,7 @@ float avpriv_scalarproduct_float_c(const float *v1, const float *v2, int len);
 void ff_float_dsp_init_aarch64(AVFloatDSPContext *fdsp);
 void ff_float_dsp_init_arm(AVFloatDSPContext *fdsp);
 void ff_float_dsp_init_ppc(AVFloatDSPContext *fdsp, int strict);
+void ff_float_dsp_init_riscv(AVFloatDSPContext *fdsp);
 void ff_float_dsp_init_x86(AVFloatDSPContext *fdsp);
 void ff_float_dsp_init_mips(AVFloatDSPContext *fdsp);
 

libavutil/riscv/Makefile

-OBJS += riscv/cpu.o
+OBJS +=     riscv/float_dsp_init.o \
+            riscv/cpu.o
+RVV-OBJS += riscv/float_dsp_rvv.o

libavutil/riscv/float_dsp_init.c

+/*
+ * 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 <stdint.h>
+
+#include "config.h"
+#include "libavutil/attributes.h"
+#include "libavutil/cpu.h"
+#include "libavutil/float_dsp.h"
+
+void ff_vector_fmul_scalar_rvv(float *dst, const float *src, float mul,
+                                int len);
+
+av_cold void ff_float_dsp_init_riscv(AVFloatDSPContext *fdsp)
+{
+#if HAVE_RVV
+    int flags = av_get_cpu_flags();
+
+    if (flags & AV_CPU_FLAG_RVV_F32)
+        fdsp->vector_fmul_scalar = ff_vector_fmul_scalar_rvv;
+#endif
+}

libavutil/riscv/float_dsp_rvv.S

+/*
+ * 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 "asm.S"
+
+// (a0) = (a1) * fa0 [0..a2-1]
+func ff_vector_fmul_scalar_rvv, zve32f
+NOHWF   fmv.w.x  fa0, a2
+NOHWF   mv       a2, a3
+1:
+        vsetvli  t0, a2, e32, m1, ta, ma
+        vle32.v  v16, (a1)
+        sub      a2, a2, t0
+        vfmul.vf v16, v16, fa0
+        sh2add   a1, t0, a1
+        vse32.v  v16, (a0)
+        sh2add   a0, t0, a0
+        bnez     a2, 1b
+
+        ret
+endfunc