Phase 62: C7 ULTRA Hotpath Optimization - Planning & Profiling Analysis

Complete planning for Phase 62 based on runtime profiling of Phase 59b baseline.

Key Findings (200M ops Mixed benchmark):
- tiny_c7_ultra_alloc: 5.18% (new primary target, 5x larger than Phase 61)
- tiny_region_id_write_header: 3.82% (reconfirmed, Phase 61 showed 2.32%)
- Allocation-specific hot path: 12.37% (C7 + header + cache)

Phase 62 Recommendation: Option A (C7 ULTRA Inline + IPC Analysis)
- Expected gain: +1-3% (higher absolute margin than Phases 46A/61)
- Risk level: Medium (layout tax precedent from Phase 46A -0.68%, Phase 43 -1.18%)
- Approach: Deep profiling → ASM inspection → A/B test with ENV gate

Alternative Options:
- Option B: tiny_region_id_write_header (3.82%, higher risk)
- Option C: Algorithmic redesign (post-50% milestone)

Box Theory Compliance:
- Single conversion point: tiny_c7_ultra_alloc() boundary
- Reversible: ENV gate HAKMEM_TINY_C7_ULTRA_INLINE_OPT (0/1)
- No side effects: Pure dependency chain reordering

Timeline: Single phase, 4-6 hours (profile + ASM + test)

Documentation:
- PHASE62_NEXT_TARGET_ANALYSIS.md: Complete planning document with profiling data
- CURRENT_TASK.md: Updated next phase guidance

Profiling tools prepared:
- perf record with extended events (cycles, cache-misses, branch-misses)
- ASM inspection methodology documented
- A/B test threshold: ±0.5% (micro-scale)

🤖 Generated with Claude Code

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

CURRENT_TASK.md

@@ -36,11 +36,21 @@
 
 ## 3) 次の指示書
 
-**Phase 62: 次（TBD）**
+**Phase 62: C7 ULTRA Hotpath Optimization - Planning Complete**
 
-- Phase 61 が NEUTRAL (+0.31%) だったため、次のターゲットを探索する
-- Runtime profiling で Top 50 のホット関数を確認（Phase 61: `tiny_region_id_write_header` 2.32%, `tiny_c7_ultra_alloc` 1.90%）
-- 候補: TLS prefetch optimization, refill batch size tuning, IPC profiling
+Phase 59b・61 完了後、runtime profiling により次のターゲット特定:
+
+- **新 Profile**: 200M ops Mixed benchmark (Speed-first mode)
+  - tiny_c7_ultra_alloc: **5.18%** (2.41% self + multi-stack overhead)
+  - tiny_region_id_write_header: **3.82%** (2.72% + 1.10%)
+  - unified_cache_push: 1.37% (Phase 46A already pursued)
+
+- **Phase 62 推奨**: C7 ULTRA Inline + IPC Analysis
+  - Option A: tiny_c7_ultra_alloc dependency chain reordering (+1-3% expected)
+  - Option B: tiny_region_id_write_header reordering (+0.5-1.5%, higher risk)
+  - Option C: Algorithmic redesign (post-50% milestone)
+
+詳細: `docs/analysis/PHASE62_NEXT_TARGET_ANALYSIS.md`（完了、ready for implementation）
 
 **Phase 61: 完了（NEUTRAL +0.31%, research box）**