With the default-argument statement bug fixed, the borrowed-local
elision blocked in 91f44ec is sound and enabled: a const-string argument
that is a plain local or by-value/const parameter variable emits no
caller pin at all — the frame's own reference outlives the call.
Exclusions guard the aliasing edges: address-taken locals (explicit @,
passed to var/out params), locals captured by nested procedures (both
via a per-function blocklist rebuilt in EmitVarAllocs), and calls whose
signature has a var/out string param (F(L, L) lets the callee release
L's buffer through the alias). Nine IR contract tests cover every
shape, including the new exclusion guards.
Tail wins on the remaining profile:
- QBEMangle: fast path returns the input unchanged when it contains no
mangled characters (1.3M calls were rebuilding clean names one concat
per character).
- TStringList.FindSorted: compares the probe slot in place through the
CompareStr/CompareText builtins instead of copying it into a local
and dispatching through Compare — several ARC ops per binary-search
step on the hottest lookup path.
- _StringFormatN: the sizing pass uses a pure DecimalWidth count
instead of rendering every %d argument twice.
Compiler self-compile: 0.78 s -> 0.60 s wall, 8.60G -> 6.45G
instructions. Verified through two self-hosted generations, gen-2
native emission, both fixpoints and the full suite (2870 tests).
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