vf_blend: Add SSE2 optimization for multiply

5 times faster than C, 3 times overall.

libavfilter/x86/vf_blend.asm

@@ -24,6 +24,7 @@
 
 SECTION_RODATA
 
+pw_1:   times 8 dw 1
 pw_128: times 8 dw 128
 pw_255: times 8 dw 255
 pb_127: times 16 db 127
@@ -101,6 +102,34 @@ BLEND_INIT difference128, 4
     jl .loop
 BLEND_END
 
+BLEND_INIT multiply, 4
+    pxor       m2, m2
+    mova       m3, [pw_1]
+.nextrow:
+    mov        xq, widthq
+
+    .loop:
+                                             ;     word
+                                             ;     |--|
+        movh            m0, [topq + xq]      ; 0000xxxx
+        movh            m1, [bottomq + xq]
+        punpcklbw       m0, m2               ; 00xx00xx
+        punpcklbw       m1, m2
+
+        pmullw          m0, m1               ; xxxxxxxx  a * b
+        paddw           m0, m3
+        mova            m1, m0
+        psrlw           m1, 8
+        paddw           m0, m1
+        psrlw           m0, 8                ; 00xx00xx  a * b / 255
+
+        packuswb        m0, m0               ; 0000xxxx
+        movh   [dstq + xq], m0
+        add             xq, mmsize / 2
+
+    jl .loop
+BLEND_END
+
 BLEND_INIT average, 3
     pxor       m2, m2
 .nextrow:

libavfilter/x86/vf_blend_init.c

@@ -36,6 +36,7 @@ BLEND_FUNC(average, sse2)
 BLEND_FUNC(and, sse2)
 BLEND_FUNC(darken, sse2)
 BLEND_FUNC(difference128, sse2)
+BLEND_FUNC(multiply, sse2)
 BLEND_FUNC(hardmix, sse2)
 BLEND_FUNC(lighten, sse2)
 BLEND_FUNC(or, sse2)
@@ -61,6 +62,7 @@ av_cold void ff_blend_init_x86(FilterParams *param, int is_16bit)
         case BLEND_DIFFERENCE128: param->blend = ff_blend_difference128_sse2; break;
         case BLEND_HARDMIX:  param->blend = ff_blend_hardmix_sse2;  break;
         case BLEND_LIGHTEN:  param->blend = ff_blend_lighten_sse2;  break;
+        case BLEND_MULTIPLY: param->blend = ff_blend_multiply_sse2; break;
         case BLEND_OR:       param->blend = ff_blend_or_sse2;       break;
         case BLEND_PHOENIX:  param->blend = ff_blend_phoenix_sse2;  break;
         case BLEND_SUBTRACT: param->blend = ff_blend_subtract_sse2; break;