riscv: test for assembler support

This should fix the build on LLVM 16 and earlier, at the cost of turning
all non-RVV optimisations off.

(cherry picked from commit b3825bbe45)
Signed-off-by: Brad Smith <brad@comstyle.com>

libavcodec/riscv/Makefile

@@ -1,14 +1,14 @@
 OBJS-$(CONFIG_AAC_DECODER) += riscv/aacpsdsp_init.o
 RVV-OBJS-$(CONFIG_AAC_DECODER) += riscv/aacpsdsp_rvv.o
-OBJS-$(CONFIG_AC3DSP) += riscv/ac3dsp_init.o \
-                         riscv/ac3dsp_rvb.o
+OBJS-$(CONFIG_AC3DSP) += riscv/ac3dsp_init.o
+RV-OBJS-$(CONFIG_AC3DSP) += riscv/ac3dsp_rvb.o
 OBJS-$(CONFIG_ALAC_DECODER) += riscv/alacdsp_init.o
 RVV-OBJS-$(CONFIG_ALAC_DECODER) += riscv/alacdsp_rvv.o
-OBJS-$(CONFIG_AUDIODSP) += riscv/audiodsp_init.o \
-                           riscv/audiodsp_rvf.o
+OBJS-$(CONFIG_AUDIODSP) += riscv/audiodsp_init.o
+RV-OBJS-$(CONFIG_AUDIODSP) += riscv/audiodsp_rvf.o
 RVV-OBJS-$(CONFIG_AUDIODSP) += riscv/audiodsp_rvv.o
-OBJS-$(CONFIG_BSWAPDSP) += riscv/bswapdsp_init.o \
-                           riscv/bswapdsp_rvb.o
+OBJS-$(CONFIG_BSWAPDSP) += riscv/bswapdsp_init.o
+RV-OBJS-$(CONFIG_BSWAPDSP) += riscv/bswapdsp_rvb.o
 RVV-OBJS-$(CONFIG_BSWAPDSP) += riscv/bswapdsp_rvv.o
 OBJS-$(CONFIG_EXR_DECODER) += riscv/exrdsp_init.o
 RVV-OBJS-$(CONFIG_EXR_DECODER) += riscv/exrdsp_rvv.o
@@ -22,8 +22,8 @@ OBJS-$(CONFIG_IDCTDSP) += riscv/idctdsp_init.o
 RVV-OBJS-$(CONFIG_IDCTDSP) += riscv/idctdsp_rvv.o
 OBJS-$(CONFIG_OPUS_DECODER) += riscv/opusdsp_init.o
 RVV-OBJS-$(CONFIG_OPUS_DECODER) += riscv/opusdsp_rvv.o
-OBJS-$(CONFIG_PIXBLOCKDSP) += riscv/pixblockdsp_init.o \
-                              riscv/pixblockdsp_rvi.o
+OBJS-$(CONFIG_PIXBLOCKDSP) += riscv/pixblockdsp_init.o
+RV-OBJS-$(CONFIG_PIXBLOCKDSP) += riscv/pixblockdsp_rvi.o
 RVV-OBJS-$(CONFIG_PIXBLOCKDSP) += riscv/pixblockdsp_rvv.o
 OBJS-$(CONFIG_VORBIS_DECODER) += riscv/vorbisdsp_init.o
 RVV-OBJS-$(CONFIG_VORBIS_DECODER) += riscv/vorbisdsp_rvv.o

libavcodec/riscv/ac3dsp_init.c

@@ -29,10 +29,12 @@ void ff_extract_exponents_rvb(uint8_t *exp, int32_t *coef, int nb_coefs);
 
 av_cold void ff_ac3dsp_init_riscv(AC3DSPContext *c)
 {
+#if HAVE_RV
     int flags = av_get_cpu_flags();
 
     if (flags & AV_CPU_FLAG_RVB_ADDR) {
         if (flags & AV_CPU_FLAG_RVB_BASIC)
             c->extract_exponents = ff_extract_exponents_rvb;
     }
+#endif
 }

libavcodec/riscv/audiodsp_init.c

@@ -33,6 +33,7 @@ void ff_vector_clipf_rvv(float *dst, const float *src, int len, float min, float
 
 av_cold void ff_audiodsp_init_riscv(AudioDSPContext *c)
 {
+#if HAVE_RV
     int flags = av_get_cpu_flags();
 
     if (flags & AV_CPU_FLAG_RVF)
@@ -47,4 +48,5 @@ av_cold void ff_audiodsp_init_riscv(AudioDSPContext *c)
             c->vector_clipf = ff_vector_clipf_rvv;
     }
 #endif
+#endif
 }

libavcodec/riscv/bswapdsp_init.c

@@ -30,6 +30,7 @@ void ff_bswap16_buf_rvv(uint16_t *dst, const uint16_t *src, int len);
 
 av_cold void ff_bswapdsp_init_riscv(BswapDSPContext *c)
 {
+#if HAVE_RV
     int flags = av_get_cpu_flags();
 
     if (flags & AV_CPU_FLAG_RVB_ADDR) {
@@ -42,4 +43,5 @@ av_cold void ff_bswapdsp_init_riscv(BswapDSPContext *c)
             c->bswap16_buf = ff_bswap16_buf_rvv;
 #endif
     }
+#endif
 }

libavcodec/riscv/pixblockdsp_init.c

@@ -43,6 +43,7 @@ av_cold void ff_pixblockdsp_init_riscv(PixblockDSPContext *c,
                                        AVCodecContext *avctx,
                                        unsigned high_bit_depth)
 {
+#if HAVE_RV
     int cpu_flags = av_get_cpu_flags();
 
     if (cpu_flags & AV_CPU_FLAG_RVI) {
@@ -62,4 +63,5 @@ av_cold void ff_pixblockdsp_init_riscv(PixblockDSPContext *c,
         c->diff_pixels_unaligned = c->diff_pixels = ff_diff_pixels_rvv;
     }
 #endif
+#endif
 }