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Number of instructions in fdct4_1d_sse2 reduced by two.

Mathematically the results are the same.

Change-Id: I1c5126cd3ca64e8515ca6331e0989c6f7dd651a0

--- a/vp9/encoder/x86/vp9_dct_sse2.c

+++ b/vp9/encoder/x86/vp9_dct_sse2.c

@@ -171,22 +171,21 @@

 void fdct4_1d_sse2(__m128i *in) {

   const __m128i k__cospi_p16_p16 = _mm_set1_epi16(cospi_16_64);

   const __m128i k__cospi_p16_m16 = pair_set_epi16(cospi_16_64, -cospi_16_64);

-  const __m128i k__cospi_p24_p08 = pair_set_epi16(cospi_24_64, cospi_8_64);

-  const __m128i k__cospi_m08_p24 = pair_set_epi16(-cospi_8_64, cospi_24_64);

+  const __m128i k__cospi_p08_p24 = pair_set_epi16(cospi_8_64, cospi_24_64);

+  const __m128i k__cospi_p24_m08 = pair_set_epi16(cospi_24_64, -cospi_8_64);

   const __m128i k__DCT_CONST_ROUNDING = _mm_set1_epi32(DCT_CONST_ROUNDING);

   __m128i u[4], v[4];

-  u[0] = _mm_add_epi16(in[0], in[3]);

-  u[1] = _mm_add_epi16(in[1], in[2]);

-  u[2] = _mm_sub_epi16(in[1], in[2]);

-  u[3] = _mm_sub_epi16(in[0], in[3]);

+  u[0]=_mm_unpacklo_epi16(in[0], in[1]);

+  u[1]=_mm_unpacklo_epi16(in[3], in[2]);

-  v[0] = _mm_unpacklo_epi16(u[0], u[1]);

-  v[1] = _mm_unpacklo_epi16(u[2], u[3]);

+  v[0] = _mm_add_epi16(u[0], u[1]);

+  v[1] = _mm_sub_epi16(u[0], u[1]);

+

   u[0] = _mm_madd_epi16(v[0], k__cospi_p16_p16);  // 0

   u[1] = _mm_madd_epi16(v[0], k__cospi_p16_m16);  // 2

-  u[2] = _mm_madd_epi16(v[1], k__cospi_p24_p08);  // 1

-  u[3] = _mm_madd_epi16(v[1], k__cospi_m08_p24);  // 3

+  u[2] = _mm_madd_epi16(v[1], k__cospi_p08_p24);  // 1

+  u[3] = _mm_madd_epi16(v[1], k__cospi_p24_m08);  // 3

   v[0] = _mm_add_epi32(u[0], k__DCT_CONST_ROUNDING);

   v[1] = _mm_add_epi32(u[1], k__DCT_CONST_ROUNDING);