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Francisco Geiman Thiesen
f902769b35
* builder: force-inline atom templates and replace integer writer
Two complementary changes that together speed up reflection-driven JSON
serialization by ~28% on integer-heavy structs (CITM) and ~12% on
string-heavy structs (Twitter).
(1) Add simdjson_really_inline (always_inline) to the hot atom<T>
template overloads (arithmetic, struct, container, optional,
string-like). The constexpr-only declaration was only a hint; the
compiler routinely chose to leave atom<unsigned long> as a real
out-of-line function.
(2) Replace string_builder::append<UInt> body with a forward
cascade-on-magnitude integer writer. The old code computed
digit_count(v) upfront and wrote backward in a loop; the new code is
a straight-line if/else cascade that writes digits forward, no loop,
no helper call.
Either change alone gives only modest gains. Together they unlock the
compiler's cross-call optimization: with all atoms inlined and the
integer writer reduced to straight-line code, the compiler can hoist
b.position into a register across the whole struct serialization, fold
redundant capacity_check calls, and eliminate the strict-aliasing
penalty that otherwise forces b.position/b.capacity reloads after every
char* write.
Output is byte-identical to master on CITM (496682 bytes) and Twitter
(81927 bytes). All static_reflection_comprehensive_tests pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* builder: de-recurse write_uint_jeaiii so always_inline applies on g++/MSVC
g++ ('inlining failed in call to always_inline ...: function not
considered for inlining') and MSVC ('warning C4714: __forceinline not
inlined' under warnings-as-errors) both refuse to inline recursive
functions marked simdjson_really_inline. The original write_uint_jeaiii
called itself in the >=10^4 branches.
Refactor into a non-recursive DAG of helpers: write_lt100, write_lt10000,
write_4_digits, write_lt1e8, write_uint_jeaiii. Each calls strictly
smaller-domain helpers, no cycles. Same straight-line cascade behavior,
same byte output, but every node is now a candidate for always_inline on
all compilers.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* builder: port signed-int append to jeaiii writer and drop digit_count helpers
The signed-integer branch in string_builder::append was structurally
identical to the OLD unsigned branch — same digit_count() upfront +
backward 4-digit batched loop. Port it to use the same forward
write_uint_jeaiii() helper as the unsigned branch (write '-'
unconditionally and advance position only if negative — branchless).
This makes int_log2 / fast_digit_count_32 / fast_digit_count_64 /
digit_count fully unused (verified via grep across include/ and src/);
remove them, ~80 lines of dead code.
The signed write path now benefits from the same compiler-level
optimization (full inlining, capacity-check fusion, no opaque-loop
boundary) as the unsigned path. Signed-int microbench (200 × 100k
values, mixed magnitude and sign): 2272 → 2685 MB/s (+18.2%).
CITM and Twitter benchmarks unchanged in shape and remain byte-identical
to baseline output.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* fix tests
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Daniel Lemire <daniel@lemire.me>