The strings of a document that had escape sequences are written in runs
without a quote, backslash, or control character; the compact dump found the
end of a run 8 bytes at a time with a SWAR test. With SSE2 (x86-64) it now
compares 16 bytes per step. NEON keeps the SWAR code: there the mask of a
step costs more than it saves on the short runs that are typical here.
Instructions of dump(), Linux (GCC 13 / Clang 18):
twitter.json 1.99M -> 1.88M (-5.2 %) / 1.97M -> 1.92M (-3.0 %)
CJK text with \u escapes 5.98M -> 4.52M (-24.5 %) / 5.30M -> 4.25M (-19.9 %)
ASCII text with a few escapes 4.28M -> 4.09M (-4.4 %) / 4.24M -> 4.11M (-3.2 %)
jeopardy (4,000 questions) 5.08M -> 4.78M (-5.8 %) / 4.97M -> 4.80M (-3.4 %)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann
cc946adf68