x86: lpc: simd av_evaluate_lls

1.5x-1.8x faster on sandybridge
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavutil/x86/lls.asm

@@ -194,3 +194,41 @@ cglobal update_lls, 3,6,8, ctx, var, count, i, j, count2
     jle .loop2x1
 .ret:
     REP_RET
+
+
+INIT_XMM sse2
+cglobal evaluate_lls, 2,4,2, ctx, var, order, i
+    ; This function is often called on the same buffer as update_lls, but with
+    ; an offset. They can't both be aligned.
+    ; Load halves rather than movu to avoid store-forwarding stalls, since the
+    ; input was initialized immediately prior to this function using scalar math.
+    %define coefsq ctxq
+    mov     id, orderd
+    imul    orderd, MAX_VARS
+    lea     coefsq, [ctxq + LLSModel.coeff + orderq*8]
+    movsd   m0, [varq]
+    movhpd  m0, [varq + 8]
+    mulpd   m0, [coefsq]
+    lea coefsq, [coefsq + iq*8]
+    lea   varq, [varq + iq*8]
+    neg     iq
+    add     iq, 2
+.loop:
+    movsd   m1, [varq + iq*8]
+    movhpd  m1, [varq + iq*8 + 8]
+    mulpd   m1, [coefsq + iq*8]
+    addpd   m0, m1
+    add     iq, 2
+    jl .loop
+    jg .skip1
+    movsd   m1, [varq + iq*8]
+    mulsd   m1, [coefsq + iq*8]
+    addpd   m0, m1
+.skip1:
+    movhlps m1, m0
+    addsd   m0, m1
+%if ARCH_X86_32
+    movsd  r0m, m0
+    fld   qword r0m
+%endif
+    RET

libavutil/x86/lls_init.c

@@ -25,12 +25,15 @@
 
 void ff_update_lls_sse2(LLSModel *m, double *var);
 void ff_update_lls_avx(LLSModel *m, double *var);
+double ff_evaluate_lls_sse2(LLSModel *m, double *var, int order);
 
 av_cold void ff_init_lls_x86(LLSModel *m)
 {
     int cpu_flags = av_get_cpu_flags();
     if (EXTERNAL_SSE2(cpu_flags)) {
         m->update_lls = ff_update_lls_sse2;
+        if (m->indep_count >= 4)
+            m->evaluate_lls = ff_evaluate_lls_sse2;
     }
     if (EXTERNAL_AVX(cpu_flags)) {
         m->update_lls = ff_update_lls_avx;