Add v4 C7/C6 fast classify and small-segment v4 scaffolding

core/box/smallobject_hotbox_v4_box.h

@@ -5,8 +5,9 @@
 //   - 挙動はまだ v3/v1 のまま。alloc/free 本体は後続フェーズで実装する。
 #pragma once
 
-#include <stdint.h>
 #include <stddef.h>
+#include <stdbool.h>
+#include <stdint.h>
 
 #include "tiny_geometry_box.h"
 
@@ -46,3 +47,4 @@ small_heap_ctx_v4* small_heap_ctx_v4_get(void);
 // Hot path API (C7-only stub; later phases will expand)
 void* small_heap_alloc_fast_v4(small_heap_ctx_v4* ctx, int class_idx);
 void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr);
+int smallobject_hotbox_v4_can_own(int class_idx, void* ptr);

core/box/smallobject_hotbox_v4_env_box.h

@@ -47,3 +47,7 @@ static inline int small_heap_v4_c7_enabled(void) {
 static inline int small_heap_v4_c6_enabled(void) {
     return small_heap_v4_class_enabled(6);
 }
+
+static inline int small_heap_v4_c5_enabled(void) {
+    return small_heap_v4_class_enabled(5);
+}

core/box/smallsegment_v4_box.h

@@ -0,0 +1,11 @@
+// smallsegment_v4_box.h - Small-object専用 Segment Box の宣言だけを置く足場
+// Phase PF2: 挙動はまだ変えず、型と API だけを先行定義する。
+#pragma once
+
+typedef struct small_segment_v4 small_segment_v4;
+
+// class_idx ごとに小さな Segment を確保/再利用する想定。
+// まだ実装はなく、次フェーズで Superslab/OS との接続を決める。
+small_segment_v4* smallsegment_v4_acquire(int class_idx);
+void* smallsegment_v4_alloc_page(small_segment_v4* seg, int class_idx);
+void smallsegment_v4_release_if_empty(small_segment_v4* seg);

core/box/smallsegment_v4_env_box.h

@@ -0,0 +1,28 @@
+// smallsegment_v4_env_box.h - small-object segment v4 の ENV ゲート
+// Phase PF2: ENV を宣言するだけ。実装は次フェーズで追加。
+#pragma once
+
+#include <stdlib.h>
+
+static inline int smallsegment_v4_enabled(void) {
+    static int g = -1;
+    if (__builtin_expect(g == -1, 0)) {
+        const char* e = getenv("HAKMEM_SMALL_SEGMENT_V4_ENABLED");
+        if (e && *e && *e != '0') {
+            g = 1;
+        } else {
+            g = 0;
+        }
+    }
+    return g;
+}
+
+static inline const char* smallsegment_v4_size_env(void) {
+    static int g_init = 0;
+    static const char* g_val = NULL;
+    if (__builtin_expect(!g_init, 0)) {
+        g_val = getenv("HAKMEM_SMALL_SEGMENT_V4_SIZE");
+        g_init = 1;
+    }
+    return g_val;
+}

core/box/tiny_front_v3_env_box.h

@@ -77,6 +77,16 @@ static inline bool tiny_ptr_fast_classify_enabled(void) {
     return g != 0;
 }
 
+// C7/C6 v4 free 用 fast classify gate (default OFF)
+static inline bool tiny_ptr_fast_classify_v4_enabled(void) {
+    static int g = -1;
+    if (__builtin_expect(g == -1, 0)) {
+        const char* e = getenv("HAKMEM_TINY_PTR_FAST_CLASSIFY_V4_ENABLED");
+        g = (e && *e && *e != '0') ? 1 : 0;
+    }
+    return g != 0;
+}
+
 // Optional stats gate
 static inline bool tiny_front_v3_stats_enabled(void) {
     static int g = -1;

core/front/malloc_tiny_fast.h

@@ -252,6 +252,15 @@ static inline int free_tiny_fast(void* ptr) {
     }
 
     tiny_route_kind_t route = tiny_route_for_class((uint8_t)class_idx);
+
+    if ((class_idx == 7 || class_idx == 6) &&
+        route == TINY_ROUTE_SMALL_HEAP_V4 &&
+        tiny_ptr_fast_classify_v4_enabled() &&
+        smallobject_hotbox_v4_can_own(class_idx, base)) {
+        small_heap_free_fast_v4(small_heap_ctx_v4_get(), class_idx, base);
+        return 1;
+    }
+
     const int use_tiny_heap = tiny_route_is_heap_kind(route);
     const TinyFrontV3Snapshot* front_snap =
         __builtin_expect(tiny_front_v3_enabled(), 0) ? tiny_front_v3_snapshot_get() : NULL;
@@ -319,7 +328,7 @@ static inline int free_tiny_fast(void* ptr) {
                     if (__builtin_expect(use_tiny_heap, 0)) {
                         switch (route) {
                             case TINY_ROUTE_SMALL_HEAP_V4:
-                                if (class_idx == 7 || class_idx == 6) {
+                                if (class_idx == 7 || class_idx == 6 || class_idx == 5) {
                                     small_heap_free_fast_v4(small_heap_ctx_v4_get(), class_idx, base);
                                     return 1;
                                 }

core/smallobject_hotbox_v4.c

@@ -1,6 +1,6 @@
-// smallobject_hotbox_v4.c - SmallObject HotHeap v4 (C7-only real path)
+// smallobject_hotbox_v4.c - SmallObject HotHeap v4 (C5/C6/C7 opt-in)
 //
-// Phase v4-3: C7 クラスについては v4 独自の freelist/current/partial で完結させる。
+// Phase v4-3.1: C7 は v4 独自の freelist/current/partial で完結。C6/C5 は強ゲート付きで同形パスを使う。
 
 #include <stdlib.h>
 #include <string.h>
@@ -17,8 +17,6 @@
 // TLS context
 static __thread small_heap_ctx_v4 g_ctx_v4;
 
-#define V4_MAX_PARTIAL_PAGES 1
-
 small_heap_ctx_v4* small_heap_ctx_v4_get(void) {
     return &g_ctx_v4;
 }
@@ -27,6 +25,10 @@ small_heap_ctx_v4* small_heap_ctx_v4_get(void) {
 // helpers
 // -----------------------------------------------------------------------------
 
+static inline int v4_class_supported(int class_idx) {
+    return class_idx == 7 || class_idx == 6 || class_idx == 5;
+}
+
 static inline void v4_page_push_partial(small_class_heap_v4* h, small_page_v4* page) {
     if (!h || !page) return;
     page->next = h->partial_head;
@@ -53,6 +55,11 @@ static inline void v4_page_push_full(small_class_heap_v4* h, small_page_v4* page
     h->full_head = page;
 }
 
+static inline uint32_t v4_partial_limit(int class_idx) {
+    // C7 は refill/retire を抑えるため少し広めに保持
+    return (class_idx == 7) ? 2u : 1u;
+}
+
 static inline int v4_ptr_in_page(const small_page_v4* page, const uint8_t* ptr) {
     if (!page || !ptr) return 0;
     uint8_t* base = page->base;
@@ -97,16 +104,32 @@ static small_page_v4* v4_find_page(small_class_heap_v4* h, const uint8_t* ptr, v
             return p;
         }
     }
-    // full リストは探さない（v4 C7 は partial/current だけで完結する想定）
+    for (small_page_v4* p = h->full_head; p; prev = p, p = p->next) {
+        if (v4_ptr_in_page(p, ptr)) {
+            if (loc) *loc = V4_LOC_FULL;
+            if (prev_out) *prev_out = prev;
+            return p;
+        }
+    }
     return NULL;
 }
 
+int smallobject_hotbox_v4_can_own(int class_idx, void* ptr) {
+    if (__builtin_expect(!v4_class_supported(class_idx), 0)) return 0;
+    if (!small_heap_v4_class_enabled((uint8_t)class_idx)) return 0;
+    if (!ptr) return 0;
+    small_heap_ctx_v4* ctx = small_heap_ctx_v4_get();
+    if (!ctx) return 0;
+    small_class_heap_v4* h = &ctx->cls[class_idx];
+    return v4_find_page(h, (const uint8_t*)ptr, NULL, NULL) != NULL;
+}
+
 // -----------------------------------------------------------------------------
-// Cold iface (C7-only, Tiny v1 経由)
+// Cold iface (C5/C6/C7, Tiny v1 経由)
 // -----------------------------------------------------------------------------
 
 static small_page_v4* cold_refill_page_v4(small_heap_ctx_v4* hot_ctx, uint32_t class_idx) {
-    if (__builtin_expect(class_idx != 7 && class_idx != 6, 0)) return NULL;
+    if (__builtin_expect(!v4_class_supported((int)class_idx), 0)) return NULL;
     (void)hot_ctx;
     tiny_heap_ctx_t* tctx = tiny_heap_ctx_for_thread();
     if (!tctx) return NULL;
@@ -163,13 +186,14 @@ const SmallColdIfaceV4* small_cold_iface_v4_get(void) {
 
 static small_page_v4* small_alloc_slow_v4(small_heap_ctx_v4* ctx, int class_idx) {
     small_class_heap_v4* h = &ctx->cls[class_idx];
+    const uint32_t partial_limit = v4_partial_limit(class_idx);
     small_page_v4* cur = h->current;
     if (cur && cur->freelist) {
         return cur;  // usable current
     }
     if (cur && !cur->freelist) {
         // current をいったん partial/full に退避（partial を優先）
-        if (h->partial_count < V4_MAX_PARTIAL_PAGES) {
+        if (h->partial_count < partial_limit) {
             v4_page_push_partial(h, cur);
         } else {
             v4_page_push_full(h, cur);
@@ -193,8 +217,8 @@ static small_page_v4* small_alloc_slow_v4(small_heap_ctx_v4* ctx, int class_idx)
 }
 
 void* small_heap_alloc_fast_v4(small_heap_ctx_v4* ctx, int class_idx) {
-    if (__builtin_expect(class_idx != 7 && class_idx != 6, 0)) {
-        return NULL;  // C6/C7 専用
+    if (__builtin_expect(!v4_class_supported(class_idx), 0)) {
+        return NULL;  // C5/C6/C7 以外は未対応
     }
     if (!small_heap_v4_class_enabled((uint8_t)class_idx)) return NULL;
     small_class_heap_v4* h = &ctx->cls[class_idx];
@@ -240,7 +264,7 @@ static void v4_unlink_from_list(small_class_heap_v4* h, v4_loc_t loc, small_page
 }
 
 void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr) {
-    if (__builtin_expect(class_idx != 7 && class_idx != 6, 0)) {
+    if (__builtin_expect(!v4_class_supported(class_idx), 0)) {
         return;
     }
     if (!small_heap_v4_class_enabled((uint8_t)class_idx)) return;
@@ -252,6 +276,8 @@ void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr) {
     small_page_v4* page = v4_find_page(h, (const uint8_t*)ptr, &loc, &prev);
     if (!page) return;
 
+    const uint32_t partial_limit = v4_partial_limit(class_idx);
+
     // freelist push
     void* head = page->freelist;
     memcpy(ptr, &head, sizeof(void*));
@@ -274,7 +300,7 @@ void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr) {
             page->next = NULL;
             return;
         }
-        if (h->partial_count < V4_MAX_PARTIAL_PAGES) {
+        if (h->partial_count < partial_limit) {
             v4_page_push_partial(h, page);
             return;
         }
@@ -296,7 +322,7 @@ void small_heap_free_fast_v4(small_heap_ctx_v4* ctx, int class_idx, void* ptr) {
     } else if (loc == V4_LOC_FULL && page->freelist) {
         // full → partial に戻す（current があっても partial 上限までは復帰）
         v4_unlink_from_list(h, loc, prev, page);
-        if (h->partial_count < V4_MAX_PARTIAL_PAGES) {
+        if (h->partial_count < partial_limit) {
             v4_page_push_partial(h, page);
         } else {
             v4_page_push_full(h, page);  // 上限超なら戻す