Implement arena allocator, add preprocessor arena

alloc.c

@@ -17,7 +17,14 @@ const char *__asan_default_options(void) {
 #endif
 
 #define FREE_THRESHOLD (100 * 1024)
+#define PAGE_SIZE 4064
 
+struct Page {
+  char buf[PAGE_SIZE];
+  Page *next;
+};
+
+Arena pp_arena;
 bool free_alloc;
 
 bool check_mem_usage(void) {
@@ -29,3 +36,69 @@ bool check_mem_usage(void) {
   return stat.ru_maxrss > FREE_THRESHOLD;
 #endif
 }
+
+static Page *new_page(void) {
+  Page *p = malloc(sizeof(Page));
+  p->next = NULL;
+#if USE_ASAN
+  __asan_poison_memory_region(&p->buf, PAGE_SIZE);
+#endif
+  return p;
+}
+
+static void *allocate(Arena *arena, size_t sz, bool clear) {
+  size_t aligned_sz = (sz + 15) & -16LL;
+
+  void *ptr;
+  if ((arena->used + aligned_sz) <= PAGE_SIZE) {
+    ptr = &arena->page->buf[arena->used];
+    arena->used += aligned_sz;
+  } else {
+    if (!arena->page->next)
+      arena->page->next = new_page();
+
+    arena->page = arena->page->next;
+    ptr = &arena->page->buf;
+    arena->used = aligned_sz;
+  }
+
+#if USE_ASAN
+  __asan_unpoison_memory_region(ptr, sz);
+  if (clear)
+    memset(ptr, 0, sz);
+#else
+  if (clear)
+    for (int i = 0; i < (aligned_sz >> 3); i++)
+      ((int64_t *)ptr)[i] = 0;
+#endif
+  return ptr;
+}
+
+void arena_on(Arena *arena) {
+  if (!arena->head_page)
+    arena->head_page = new_page();
+
+  arena->page = arena->head_page;
+  arena->on = true;
+  arena->used = 0;
+}
+
+void arena_off(Arena *arena) {
+  arena->on = false;
+
+  if (free_alloc) {
+    while (arena->head_page) {
+      Page *nxt = arena->head_page->next;
+      free(arena->head_page);
+      arena->head_page = nxt;
+    }
+  }
+}
+
+void *arena_malloc(Arena *a, size_t sz) {
+  return allocate(a, sz, false);
+}
+
+void *arena_calloc(Arena *a, size_t sz) {
+  return allocate(a, sz, true);
+}

preprocess.c

@@ -425,15 +425,15 @@ static void add_macro2(Macro *m, char *name, bool is_objlike, Token *body) {
 }
 
 static Macro *add_macro(char *name, bool is_objlike, Token *body) {
-  Macro *m = calloc(1, sizeof(Macro));
+  Macro *m = arena_calloc(&pp_arena, sizeof(Macro));
   add_macro2(m, name, is_objlike, body);
   return m;
 }
 
 static Macro *read_macro_params(Token **rest, Token *tok) {
   Token head = {0};
   Token *cur = &head;
-  Macro *m = calloc(1, sizeof(Macro));
+  Macro *m = arena_calloc(&pp_arena, sizeof(Macro));
 
   while (!consume(rest, tok, ")")) {
     if (m->arg_cnt++)
@@ -589,7 +589,7 @@ static MacroArg *find_arg(Token **rest, Token *tok, MacroContext *ctx) {
   // __VA_OPT__(x) is treated like a parameter which expands to parameter-
   // substituted (x) if macro-expanded __VA_ARGS__ is not empty.
   if (equal(tok, "__VA_OPT__") && equal(tok->next, "(")) {
-    MacroArg *arg = malloc(sizeof(MacroArg));
+    MacroArg *arg = arena_malloc(&pp_arena, sizeof(MacroArg));
     arg->tok = read_macro_arg_one(&tok, tok->next->next, true);
 
     if (has_non_empty_va_arg(ctx, NULL))
@@ -1551,6 +1551,8 @@ static char *format_time(struct tm *tm) {
 }
 
 void init_macros(void) {
+  arena_on(&pp_arena);
+
   // Define predefined macros
   define_macro("_LP64", "1");
   define_macro("__BYTE_ORDER__", "1234");
@@ -1791,8 +1793,10 @@ Token *preprocess(Token *tok) {
   if (opt_E)
     return tok;
 
-  if (!(free_alloc = check_mem_usage()))
+  if (!(free_alloc = check_mem_usage())) {
+    arena_off(&pp_arena);
     return preprocess3(tok);
+  }
 
   Token *t = tok;
   for (; t->kind != TK_EOF; t = t->next) {
@@ -1818,5 +1822,6 @@ Token *preprocess(Token *tok) {
   }
 
   free(cond_incl.data);
+  arena_off(&pp_arena);
   return tok;
 }

slimcc.h

@@ -61,8 +61,21 @@ typedef struct Relocation Relocation;
 //
 // alloc.c
 
+typedef struct Page Page;
+typedef struct {
+  int used;
+  bool on;
+  Page *head_page;
+  Page *page;
+} Arena;
+
+void arena_on(Arena *arena);
+void arena_off(Arena *arena);
+void *arena_calloc(Arena *a, size_t sz);
+void *arena_malloc(Arena *a, size_t sz);
 bool check_mem_usage(void);
 
+extern Arena pp_arena;
 extern bool free_alloc;
 
 //