From 6cd97cd7975ce662234687bbc8cca397d281b99a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi=20Denis-Courmont?= <remi@remlab.net>
Date: Mon, 29 Apr 2024 22:19:11 +0300
Subject: [PATCH] lavc/ac3dsp: R-V V sum_square_butterfly_float

As we do not need to widen accumulators to 64 bits, we effectively get
double capacity for unrolling compared to the integer function. This
explains the slightly better performance gains.

ac3_sum_square_bufferfly_float_c:       65.2
ac3_sum_square_bufferfly_float_rvv_f32: 12.2
---
 libavcodec/riscv/ac3dsp_init.c |  6 +++++-
 libavcodec/riscv/ac3dsp_rvv.S  | 39 ++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/libavcodec/riscv/ac3dsp_init.c b/libavcodec/riscv/ac3dsp_init.c
index be5e153fac..e120aa2dce 100644
--- a/libavcodec/riscv/ac3dsp_init.c
+++ b/libavcodec/riscv/ac3dsp_init.c
@@ -30,6 +30,8 @@ void ff_extract_exponents_rvb(uint8_t *exp, int32_t *coef, int nb_coefs);
 void ff_float_to_fixed24_rvv(int32_t *dst, const float *src, size_t len);
 void ff_sum_square_butterfly_int32_rvv(int64_t *, const int32_t *,
                                        const int32_t *, int);
+void ff_sum_square_butterfly_float_rvv(float *, const float *,
+                                       const float *, int);
 
 av_cold void ff_ac3dsp_init_riscv(AC3DSPContext *c)
 {
@@ -39,8 +41,10 @@ av_cold void ff_ac3dsp_init_riscv(AC3DSPContext *c)
     if (flags & AV_CPU_FLAG_RVB_ADDR) {
         if (flags & AV_CPU_FLAG_RVB_BASIC)
             c->extract_exponents = ff_extract_exponents_rvb;
-        if (flags & AV_CPU_FLAG_RVV_F32)
+        if (flags & AV_CPU_FLAG_RVV_F32) {
             c->float_to_fixed24 = ff_float_to_fixed24_rvv;
+            c->sum_square_butterfly_float = ff_sum_square_butterfly_float_rvv;
+        }
 # if __riscv_xlen >= 64
         if (flags & AV_CPU_FLAG_RVV_I64)
             c->sum_square_butterfly_int32 = ff_sum_square_butterfly_int32_rvv;
diff --git a/libavcodec/riscv/ac3dsp_rvv.S b/libavcodec/riscv/ac3dsp_rvv.S
index dd0b4cd797..397e000ab0 100644
--- a/libavcodec/riscv/ac3dsp_rvv.S
+++ b/libavcodec/riscv/ac3dsp_rvv.S
@@ -78,3 +78,42 @@ func ff_sum_square_butterfly_int32_rvv, zve64x
         ret
 endfunc
 #endif
+
+func ff_sum_square_butterfly_float_rvv, zve32f
+        vsetvli     t0, zero, e32, m8, ta, ma
+        vmv.v.x     v0, zero
+        vmv.v.x     v8, zero
+1:
+        vsetvli     t0, a3, e32, m4, tu, ma
+        vle32.v     v16, (a1)
+        sub         a3, a3, t0
+        vle32.v     v20, (a2)
+        sh2add      a1, t0, a1
+        vfadd.vv    v24, v16, v20
+        sh2add      a2, t0, a2
+        vfsub.vv    v28, v16, v20
+        vfmacc.vv   v0, v16, v16
+        vfmacc.vv   v4, v20, v20
+        vfmacc.vv   v8, v24, v24
+        vfmacc.vv   v12, v28, v28
+        bnez        a3, 1b
+
+        vsetvli     t0, zero, e32, m4, ta, ma
+        vmv.s.x     v16, zero
+        vmv.s.x     v17, zero
+        vfredsum.vs v16, v0, v16
+        vmv.s.x     v18, zero
+        vfredsum.vs v17, v4, v17
+        vmv.s.x     v19, zero
+        vfredsum.vs v18, v8, v18
+        vfmv.f.s    ft0, v16
+        vfredsum.vs v19, v12, v19
+        vfmv.f.s    ft1, v17
+        fsw         ft0,   (a0)
+        vfmv.f.s    ft2, v18
+        fsw         ft1,  4(a0)
+        vfmv.f.s    ft3, v19
+        fsw         ft2,  8(a0)
+        fsw         ft3, 12(a0)
+        ret
+endfunc