[FFmpeg-devel] [PATCH] lpc: rewrite lpc_compute_autocorr in external asm

[Lynne via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

The inline asm function had issues running under checkasm.
So I came to finish what I started, and wrote the last part
of LPC computation in assembly.

autocorr_10_c: 135525.8
autocorr_10_sse2: 50729.8
autocorr_10_fma3: 19007.8
autocorr_30_c: 390100.8
autocorr_30_sse2: 142478.8
autocorr_30_fma3: 50559.8
autocorr_32_c: 407058.3
autocorr_32_sse2: 151633.3
autocorr_32_fma3: 50517.3
---
 libavcodec/x86/lpc.asm    | 91 +++++++++++++++++++++++++++++++++++++++
 libavcodec/x86/lpc_init.c | 87 ++++---------------------------------
 2 files changed, 100 insertions(+), 78 deletions(-)

diff --git a/libavcodec/x86/lpc.asm b/libavcodec/x86/lpc.asm
index a585c17ef5..790841b7f4 100644
--- a/libavcodec/x86/lpc.asm
+++ b/libavcodec/x86/lpc.asm
@@ -32,6 +32,8 @@ dec_tab_sse2: times 2 dq -2.0
 dec_tab_scalar: times 2 dq -1.0
 seq_tab_sse2: dq 1.0, 0.0
 
+autoc_init_tab: times 4 dq 1.0
+
 SECTION .text
 
 %macro APPLY_WELCH_FN 0
@@ -261,3 +263,92 @@ APPLY_WELCH_FN
 INIT_YMM avx2
 APPLY_WELCH_FN
 %endif
+
+%macro COMPUTE_AUTOCORR_FN 0
+cglobal lpc_compute_autocorr, 4, 7, 8, data, len, lag, autoc, lag_p, data_l, len_p
+
+    shl lagd, 3
+    shl lenq, 3
+    xor lag_pq, lag_pq
+
+.lag_l:
+    movaps m8, [autoc_init_tab]
+
+    mov len_pq, lag_pq
+
+    lea data_lq, [lag_pq + mmsize - 8]
+    neg data_lq                     ; -j - mmsize
+    add data_lq, dataq              ; data[-j - mmsize]
+.len_l:
+    ; We waste the upper value here on SSE2,
+    ; but we use it on AVX.
+    movupd xm0, [dataq + len_pq]    ; data[i]
+    movupd m1, [data_lq + len_pq]   ; data[i - j]
+
+%if cpuflag(avx)
+    vbroadcastsd m0, xm0
+    vperm2f128 m1, m1, m1, 0x01
+%endif
+
+    shufpd m0, m0, m0, 1100b
+    shufpd m1, m1, m1, 0101b
+
+%if cpuflag(fma3)
+    fmaddpd m8, m0, m1, m8          ; sum += data[i]*data[i-j]
+%else
+    mulpd m0, m1
+    addpd m8, m0                    ; sum += data[i]*data[i-j]
+%endif
+
+    add len_pq, 8
+    cmp len_pq, lenq
+    jl .len_l
+
+    movups [autocq + lag_pq], m8    ; autoc[j] = sum
+    add lag_pq, mmsize
+    cmp lag_pq, lagq
+    jl .lag_l
+
+    ; The tail computation is guaranteed never to happen
+    ; as long as we're doing multiples of 4, rather than 2.
+    ; It is trivial to convert this to avx if ever needed.
+%if !cpuflag(avx)
+    jg .end
+    ; If lag_p == lag fallthrough
+
+.tail:
+    movaps xm2, [autoc_init_tab]
+
+    mov len_pq, lag_pq
+    sub len_pq, mmsize
+
+    lea data_lq, [lag_pq]
+    neg data_lq                     ; -j
+    add data_lq, dataq              ; data[-j]
+
+.tail_l:
+    movupd xm0, [dataq + len_pq]
+    movupd xm1, [data_lq + len_pq]
+
+    mulpd xm0, xm1
+    addpd xm2, xm0                  ; sum += data[i]*data[i-j]
+
+    add len_pq, mmsize
+    cmp len_pq, lenq
+    jl .tail_l
+
+    shufpd xm1, xm2, xm2, 01b
+    addpd xm2, xm1
+
+    movhpd [autocq + lag_pq], xm2
+%endif
+
+.end:
+    RET
+
+%endmacro
+
+INIT_XMM sse2
+COMPUTE_AUTOCORR_FN
+INIT_YMM fma3
+COMPUTE_AUTOCORR_FN
diff --git a/libavcodec/x86/lpc_init.c b/libavcodec/x86/lpc_init.c
index f2fca53799..96469fae40 100644
--- a/libavcodec/x86/lpc_init.c
+++ b/libavcodec/x86/lpc_init.c
@@ -28,89 +28,20 @@ void ff_lpc_apply_welch_window_sse2(const int32_t *data, ptrdiff_t len,
                                     double *w_data);
 void ff_lpc_apply_welch_window_avx2(const int32_t *data, ptrdiff_t len,
                                     double *w_data);
-
-DECLARE_ASM_CONST(16, double, pd_1)[2] = { 1.0, 1.0 };
-
-#if HAVE_SSE2_INLINE
-
-static void lpc_compute_autocorr_sse2(const double *data, ptrdiff_t len, int lag,
-                                      double *autoc)
-{
-    int j;
-
-    if((x86_reg)data & 15)
-        data++;
-
-    for(j=0; j<lag; j+=2){
-        x86_reg i = -len*sizeof(double);
-        if(j == lag-2) {
-            __asm__ volatile(
-                "movsd    "MANGLE(pd_1)", %%xmm0    \n\t"
-                "movsd    "MANGLE(pd_1)", %%xmm1    \n\t"
-                "movsd    "MANGLE(pd_1)", %%xmm2    \n\t"
-                "1:                                 \n\t"
-                "movapd   (%2,%0), %%xmm3           \n\t"
-                "movupd -8(%3,%0), %%xmm4           \n\t"
-                "movapd   (%3,%0), %%xmm5           \n\t"
-                "mulpd     %%xmm3, %%xmm4           \n\t"
-                "mulpd     %%xmm3, %%xmm5           \n\t"
-                "mulpd -16(%3,%0), %%xmm3           \n\t"
-                "addpd     %%xmm4, %%xmm1           \n\t"
-                "addpd     %%xmm5, %%xmm0           \n\t"
-                "addpd     %%xmm3, %%xmm2           \n\t"
-                "add       $16,    %0               \n\t"
-                "jl 1b                              \n\t"
-                "movhlps   %%xmm0, %%xmm3           \n\t"
-                "movhlps   %%xmm1, %%xmm4           \n\t"
-                "movhlps   %%xmm2, %%xmm5           \n\t"
-                "addsd     %%xmm3, %%xmm0           \n\t"
-                "addsd     %%xmm4, %%xmm1           \n\t"
-                "addsd     %%xmm5, %%xmm2           \n\t"
-                "movsd     %%xmm0,   (%1)           \n\t"
-                "movsd     %%xmm1,  8(%1)           \n\t"
-                "movsd     %%xmm2, 16(%1)           \n\t"
-                :"+&r"(i)
-                :"r"(autoc+j), "r"(data+len), "r"(data+len-j)
-                 NAMED_CONSTRAINTS_ARRAY_ADD(pd_1)
-                :"memory"
-            );
-        } else {
-            __asm__ volatile(
-                "movsd    "MANGLE(pd_1)", %%xmm0    \n\t"
-                "movsd    "MANGLE(pd_1)", %%xmm1    \n\t"
-                "1:                                 \n\t"
-                "movapd   (%3,%0), %%xmm3           \n\t"
-                "movupd -8(%4,%0), %%xmm4           \n\t"
-                "mulpd     %%xmm3, %%xmm4           \n\t"
-                "mulpd    (%4,%0), %%xmm3           \n\t"
-                "addpd     %%xmm4, %%xmm1           \n\t"
-                "addpd     %%xmm3, %%xmm0           \n\t"
-                "add       $16,    %0               \n\t"
-                "jl 1b                              \n\t"
-                "movhlps   %%xmm0, %%xmm3           \n\t"
-                "movhlps   %%xmm1, %%xmm4           \n\t"
-                "addsd     %%xmm3, %%xmm0           \n\t"
-                "addsd     %%xmm4, %%xmm1           \n\t"
-                "movsd     %%xmm0, %1               \n\t"
-                "movsd     %%xmm1, %2               \n\t"
-                :"+&r"(i), "=m"(autoc[j]), "=m"(autoc[j+1])
-                :"r"(data+len), "r"(data+len-j)
-                 NAMED_CONSTRAINTS_ARRAY_ADD(pd_1)
-            );
-        }
-    }
-}
-
-#endif /* HAVE_SSE2_INLINE */
+void ff_lpc_compute_autocorr_sse2(const double *data, ptrdiff_t len, int lag,
+                                  double *autoc);
+void ff_lpc_compute_autocorr_fma3(const double *data, ptrdiff_t len, int lag,
+                                  double *autoc);
 
 av_cold void ff_lpc_init_x86(LPCContext *c)
 {
     int cpu_flags = av_get_cpu_flags();
 
-#if HAVE_SSE2_INLINE
-    if (INLINE_SSE2_SLOW(cpu_flags))
-        c->lpc_compute_autocorr = lpc_compute_autocorr_sse2;
-#endif
+    if (EXTERNAL_SSE2(cpu_flags))
+        c->lpc_compute_autocorr = ff_lpc_compute_autocorr_sse2;
+
+    if (EXTERNAL_FMA3(cpu_flags))
+        c->lpc_compute_autocorr = ff_lpc_compute_autocorr_fma3;
 
     if (EXTERNAL_SSE2(cpu_flags))
         c->lpc_apply_welch_window = ff_lpc_apply_welch_window_sse2;
-- 
2.43.0.381.gb435a96ce8
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