2021.09.03 tests with pip version of angr:

   * portable gives warning-unrollerror with gcc -O3 since
     Iop_QNarrowBin32Sto16Ux8 isn't supported in angr.

2021.09.04 tests with angr-dev: Unrolling now works fine thanks to
https://github.com/angr/angr/pull/2887. avx=ref and portable=ref with
both compilers now, ref=ref across compilers.

2021.09.14 benchmarks, EPYC 7742:

build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native warning-mul
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native warning-mul
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native seconds unroll 15.160968
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native seconds unroll 15.492687
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native warning-mul
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native seconds unroll 17.072737
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native warning-mul
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native seconds unroll 24.376248
build/encode_761x4591/ref/clang_-O1_-fwrapv_-march_native warning-mul
build/encode_761x4591/ref/clang_-O1_-fwrapv_-march_native seconds unroll 27.501085
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native equals-ref-clang_-O1_-fwrapv_-march_native
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native seconds equiv 1.642062
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native equals-ref-clang_-O1_-fwrapv_-march_native
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native seconds equiv 1.683162
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native equals-ref-clang_-O1_-fwrapv_-march_native
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native seconds equiv 1.897204

2021.09.16 benchmarks, EPYC 7742:

build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native equals-ref-gcc_-O3_-march_native_-mtune_native
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native seconds equiv 132618.525005

2021.09.27 benchmarks, EPYC 7501:

build/encode_761x4591/portable/gcc_-O3_-march_native_-mtune_native warning-mul
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native warning-mul
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native warning-mul
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native warning-mul
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native seconds unroll 26.397915
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native seconds unroll 26.305135
build/encode_761x4591/portable/gcc_-O3_-march_native_-mtune_native seconds unroll 26.224765
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native seconds unroll 27.770387
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native warning-mul
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native seconds unroll 48.762619
build/encode_761x4591/ref/clang_-O1_-fwrapv_-march_native warning-mul
build/encode_761x4591/ref/clang_-O1_-fwrapv_-march_native seconds unroll 59.712889
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native equals-ref-clang_-O1_-fwrapv_-march_native
build/encode_761x4591/portable/clang_-O1_-fwrapv_-march_native seconds equiv 11.498500
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native equals-ref-clang_-O1_-fwrapv_-march_native
build/encode_761x4591/ref/gcc_-O3_-march_native_-mtune_native seconds equiv 8.712421
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native equals-ref-clang_-O1_-fwrapv_-march_native
build/encode_761x4591/avx/clang_-O1_-fwrapv_-march_native seconds equiv 10.741940
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native equals-ref-gcc_-O3_-march_native_-mtune_native
build/encode_761x4591/avx/gcc_-O3_-march_native_-mtune_native seconds equiv 192629.846660