Amazon A1 (AArch64) vs Amazon T2 (x64). VtxCodec uses SSSE3 on x64 and NEON on ARM. Look at revision history to see the diff.

meshoptimizer.log

a1.medium $ ./build/release/meshoptimizer buddha.obj
# buddha.obj: 549409 vertices, 1087474 triangles; read in 483.46 msec; indexed in 354.61 msec
Original : ACMR 1.556966 ATVR 3.081784 (NV 3.124747 AMD 3.277660 Intel 2.289651) Overfetch 2.105950 Overdraw 1.200370 in 0.00 msec
Random   : ACMR 2.999919 ATVR 5.937897 (NV 5.937882 AMD 5.937935 Intel 5.936783) Overfetch 10.839888 Overdraw 1.218682 in 33.38 msec
Cache    : ACMR 0.661465 ATVR 1.309272 (NV 1.590738 AMD 1.434356 Intel 1.138871) Overfetch 1.509062 Overdraw 1.206893 in 477.86 msec
CacheFifo: ACMR 0.689948 ATVR 1.365651 (NV 1.706663 AMD 1.516610 Intel 1.229416) Overfetch 1.552013 Overdraw 1.197034 in 146.00 msec
Overdraw : ACMR 2.776432 ATVR 5.495538 (NV 5.508446 AMD 5.527603 Intel 5.314811) Overfetch 8.624212 Overdraw 1.086317 in 209.29 msec
Fetch    : ACMR 1.556966 ATVR 3.081784 (NV 3.124747 AMD 3.277660 Intel 2.289651) Overfetch 2.105950 Overdraw 1.200370 in 25.13 msec
FetchMap : ACMR 1.556966 ATVR 3.081784 (NV 3.124747 AMD 3.277660 Intel 2.289651) Overfetch 2.105950 Overdraw 1.200370 in 30.68 msec
Complete : ACMR 0.667803 ATVR 1.321817 (NV 1.602355 AMD 1.446700 Intel 1.167953) Overfetch 1.242535 Overdraw 1.105052 in 628.91 msec
Stripify : ACMR 0.695596 ATVR 1.376829 (NV 1.697231 AMD 1.591876 Intel 1.139321); 1894000 strip indices (58.1%) in 81.61 msec
Meshlets : 11285 meshlets (avg vertices 64.0, avg triangles 96.4, not full 111) in 29.08 msec
ConeCull : rejected apex 2724 (24.1%) / center 2723 (24.1%), trivially accepted 540 (4.8%) in 83.73 msec
ConeCull8: rejected apex 2663 (23.6%) / center 2663 (23.6%), trivially accepted 645 (5.7%) in 83.73 msec
ShadowIB : ACMR 0.656863 (1.01x improvement); 543439 shadow vertices (1.01x improvement) in 93.90 msec
IdxCodec : 9.9 bits/triangle (post-deflate 6.2 bits/triangle); encode 51.37 msec, decode 11.71 msec (1.04 GB/s)
VtxPack  : 128.0 bits/vertex (post-deflate 63.9 bits/vertex)
VtxCodec : 45.5 bits/vertex (post-deflate 39.9 bits/vertex); encode 50.51 msec, decode 10.51 msec (0.78 GB/s)
VtxCodecO: 37.9 bits/vertex (post-deflate 33.3 bits/vertex); encode 39.87 msec, decode 8.49 msec (0.72 GB/s)
Simplify : 1087474 triangles => 5 LOD levels down to 261072 triangles in 1630.95 msec, optimized in 1810.75 msec
           ACMR 0.663601...0.685217 Overfetch 1.319371..1.201511 Codec VB 42.4 bits/vertex IB 17.2 bits/triangle