Two fixes to the ablation logic:
1. Fix incorrect branch hint in capacity_check() overflow detection
(json_string_builder-inl.h:365): simdjson_likely was used on the
overflow check `position + upcoming_bytes < position`, but overflow
is rare so this should be simdjson_unlikely. The comment itself says
"most of the time there is no overflow". This was causing the branch
predictor to optimize for the wrong path.
2. Add missing ABLATION_NO_CONSTEVAL guard in extract_from()
(json_builder.h:332): consteval_to_quoted_escaped was being used
without an ablation guard, for consistency with all other call sites.
Updated ablation results with both fixes:
| Configuration | CITM (MB/s) | Impact | Twitter (MB/s) | Impact |
|------------------|-------------|--------|----------------|--------|
| Baseline | 3001.10 | - | 5651.89 | - |
| NO_BRANCH_HINTS | 2443.67 | -19% | 4651.78 | -18% |
| NO_SIMD_ESCAPING | 2904.34 | -3% | 1403.36 | -75% |
| NO_CONSTEVAL | 1796.05 | -40% | 3542.77 | -37% |
Francisco Geiman Thiesen
2887e7432c