CharlesKWON 1f63c7fe63 perf(vm): symbol hoist + Function() stack shift — global 3-15% ...

The VM call path (PushSymbol → Function → Frame) is traversed by every
PRG function call. Three changes together cut per-call overhead across
the entire bench suite.

Changes
 - hbrt/call.go Function(): replace pop-push dance with a single slice
   shift (N+2 pops + N pushes → 1 copy of N slots + sp adjust). Kills
   the per-call `make([]Value, nArgs)` heap alloc. Resolved function
   pointer is cached back into sym.Func so subsequent calls on the
   same Symbol skip the VM lookup entirely.
 - hbrt/vm.go GetSym(): new helper. Generated code calls it with a
   pointer to a package-level `*Symbol` slot so FindSymbol (which takes
   the VM RWMutex + map lookup) runs at most once per symbol per
   process. Nil results are intentionally NOT cached — an init-order
   miss becomes a retry on the next call instead of a permanent sticky
   failure.
 - hbrt/thread.go pushPendingSym(): scalar fast slot for depth=1 call
   nesting (common case). Nil syms still go through the slice so the
   "empty vs stored nil" ambiguity can't produce a false pop.
 - compiler/gengo/gengo.go: emit `t.PushSymbol(t.GetSym(&_sym_<file>_<NAME>, "NAME"))`
   for every function call site, with a per-file prefix so multi-PRG
   builds don't collide on identical symbol names.

Bugs fixed during bring-up
 - pendingSymFast == nil was ambiguous ("unused" vs "nil stored"). Nil
   syms now spill to the slice, preserving distinguishability.
 - The old varName-reuse branch at the PushSymbol emit site skipped
   the GetSym wrapper, emitting a raw `t.PushSymbol(varName)` against
   an uninitialized package-level *Symbol. Every call path now funnels
   through emitPushSymbol.

bench_sql deltas vs prior build
 - B1  SELECT *          114 →  97 µs   (15%)
 - B4  GROUP_HAVING      584 → 554 µs   (5%)
 - B8  RECURSIVE CTE     150 → 141 µs   (6%)
 - B10 RANK PARTITION    310 → 296 µs   (5%)
 - B11 SUM OVER          335 → 320 µs   (4%)
 - B14 COUNT             295 → 281 µs   (5%)
 - B15 CTE+WIN+JOIN     1891 → 1826 µs  (3%)

Verification
 - go test ./...               ALL PASS
 - FiveSql2 test_sql1999       43/43
 - tests/compat_harbour        56/56

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-04-17 20:41:48 +09:00

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