Phase 5 E4-1: Free Wrapper ENV Snapshot (+3.51% GO, ADOPTED)

Target: Consolidate free wrapper TLS reads (2→1)
- free() is 25.26% self% (top hot spot)
- Strategy: Apply E1 success pattern (ENV snapshot) to free path

Implementation:
- ENV gate: HAKMEM_FREE_WRAPPER_ENV_SNAPSHOT=0/1 (default 0)
- core/box/free_wrapper_env_snapshot_box.{h,c}: New box
  - Consolidates 2 TLS reads → 1 TLS read (50% reduction)
  - Reduces 4 branches → 3 branches (25% reduction)
  - Lazy init with probe window (bench_profile putenv sync)
- core/box/hak_wrappers.inc.h: Integration in free() wrapper
- Makefile: Add free_wrapper_env_snapshot_box.o to all targets

A/B Test Results (Mixed, 10-run, 20M iters):
- Baseline (SNAPSHOT=0): 45.35M ops/s (mean), 45.31M ops/s (median)
- Optimized (SNAPSHOT=1): 46.94M ops/s (mean), 47.15M ops/s (median)
- Improvement: +3.51% mean, +4.07% median

Decision: GO (+3.51% >= +1.0% threshold)
- Exceeded conservative estimate (+1.5% → +3.51%)
- Similar efficiency to E1 (+3.92%)
- Health check: PASS (all profiles)
- Action: PROMOTED to MIXED_TINYV3_C7_SAFE preset

Phase 5 Cumulative:
- E1 (ENV Snapshot): +3.92%
- E4-1 (Free Wrapper Snapshot): +3.51%
- Total Phase 4-5: ~+7.5%

E3-4 Correction:
- Phase 4 E3-4 (ENV Constructor Init): NO-GO / FROZEN
- Initial A/B showed +4.75%, but investigation revealed:
  - Branch prediction hint mismatch (UNLIKELY with always-true)
  - Retest confirmed -1.78% regression
  - Root cause: __builtin_expect(..., 0) with ctor_mode==1
- Decision: Freeze as research box (default OFF)
- Learning: Branch hints need careful tuning, TLS consolidation safer

Deliverables:
- docs/analysis/PHASE5_E4_FREE_GATE_OPTIMIZATION_1_DESIGN.md
- docs/analysis/PHASE5_E4_1_FREE_WRAPPER_ENV_SNAPSHOT_NEXT_INSTRUCTIONS.md
- docs/analysis/PHASE5_E4_2_MALLOC_WRAPPER_ENV_SNAPSHOT_NEXT_INSTRUCTIONS.md (next)
- docs/analysis/PHASE5_POST_E1_NEXT_INSTRUCTIONS.md
- docs/analysis/ENV_PROFILE_PRESETS.md (E4-1 added, E3-4 corrected)
- CURRENT_TASK.md (E4-1 complete, E3-4 frozen)
- core/bench_profile.h (E4-1 promoted to default)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/analysis/PHASE4_EXECUTIVE_SUMMARY.md

@@ -1,8 +1,8 @@
 # Phase 4 Status - Executive Summary
 
 **Date**: 2025-12-14
-**Status**: E1 GO（opt-in）, E2 FROZEN, E3-4 GO（opt-in）
-**Baseline**: Mixed 20M/ws=400（E1/E3-4 の ON/OFF に依存。結果は各 A/B セクション参照）
+**Status**: E1 ✅ GO（preset昇格）, E2 🔬 FROZEN, E3-4 ❌ NO-GO
+**Baseline**: Mixed 20M/ws=400（E1=1 を前提）
 
 ---
 
@@ -27,14 +27,12 @@
 ### E1: ENV Snapshot Consolidation ✅ GO (opt-in)
 
 **Result**: +3.92% avg, +4.01% median  
-**ENV**: `HAKMEM_ENV_SNAPSHOT=1`（default OFF）
+**ENV**: `HAKMEM_ENV_SNAPSHOT=1`（`MIXED_TINYV3_C7_SAFE` で default 化、opt-out 可）
 
-### E3-4: ENV Constructor Init ✅ GO (opt-in)
+### E3-4: ENV Constructor Init ❌ NO-GO (FROZEN)
 
-**Result**: +4.75% mean, +4.35% median（E1=1 前提）  
-**ENV**: `HAKMEM_ENV_SNAPSHOT=1 HAKMEM_ENV_SNAPSHOT_CTOR=1`（default OFF）
-
-**Note**: “constructor での pre-main init” を効かせたい場合はプロセス起動前に ENV を設定（bench_profile putenv だけでは遅い）
+**Result（re-validation）**: -1.44% mean, -1.03% median（E1=1 前提）  
+**ENV**: `HAKMEM_ENV_SNAPSHOT=1 HAKMEM_ENV_SNAPSHOT_CTOR=1`（default OFF / freeze）
 
 ---
 
@@ -42,17 +40,17 @@
 
 **Active**:
 - E1 (ENV Snapshot): +3.92% ✅ GO（opt-in）
-- E3-4 (ENV CTOR): +4.75% ✅ GO（opt-in, requires E1）
 
 **Frozen**:
 - D3 (Alloc Gate Shape): +0.56% ⚪
 - E2 (Alloc Per-Class FastPath): -0.21% ⚪
+- E3-4 (ENV CTOR): ❌ NO-GO
 
 ## Next Actions
 
-1. E3-4 の “hint/refresh” 調整後に 10-run 再確認（昇格前の最終ゲート）
-2. GO 維持なら `ENV_PROFILE_PRESETS.md` と `CURRENT_TASK.md` に “E1+E3-4 の推奨セット” を明記
-3. E1/E3-4 ON の状態で perf を取り直して次の芯を選ぶ（alloc gate / free_tiny_fast_cold など）
+1. E3-4 を freeze 維持（default OFF）
+2. E1 を本線化した状態で perf を取り直し、“self% ≥ 5%” の芯を選ぶ
+3. 次の箱は “TLS/分岐” ではなく “実データ構造/ホットループ” を優先（alloc gate / unified_cache / pool など）
 
 ---