Add AVX2 version of generate_grain_uv (4:2:0)

gen_grain_uv_ar0_8bpc_420_c: 46407.4
gen_grain_uv_ar0_8bpc_420_avx2: 6718.4
gen_grain_uv_ar1_8bpc_420_c: 61715.0
gen_grain_uv_ar1_8bpc_420_avx2: 17591.5
gen_grain_uv_ar2_8bpc_420_c: 90880.3
gen_grain_uv_ar2_8bpc_420_avx2: 26969.6
gen_grain_uv_ar3_8bpc_420_c: 127393.7
gen_grain_uv_ar3_8bpc_420_avx2: 30414.7

assigned to @gramner

added performance label

resolved all threads

added 1 commit

• 7bbec816 - Add AVX2 version of generate_grain_uv (4:2:0)

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resolved all threads

added 1 commit

• 7ae3e77b - Add AVX2 version of generate_grain_uv (4:2:0)

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added 2 commits

• ff41197b - 1 commit from branch videolan:master
• 4e22ef3a - Add AVX2 version of generate_grain_uv (4:2:0)

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enabled an automatic merge when the pipeline for 4e22ef3a succeeds

merged

mentioned in issue #78

changed milestone to %0.5.0

added x86 label