@@ -22,37 +22,28 @@ class arena {
2222 initialize_semispace ();
2323 }
2424
25+ char *evacuate (char *scan_ptr);
26+
2527 // Allocates the requested number of bytes as a contiguous region and returns a
2628 // pointer to the first allocated byte.
2729 void *kore_arena_alloc (size_t requested);
2830
2931 // Returns the address of the first byte that belongs in the given arena.
30- // Returns 0 if nothing has been allocated ever in that arena.
31- char *arena_start_ptr () const {
32- return current_addr_ptr ? current_addr_ptr + sizeof (memory_block_header)
33- : nullptr ;
34- }
32+ // Returns nullptr if nothing has been allocated ever in that arena.
33+ char *arena_start_ptr () const { return current_addr_ptr; }
3534
3635 // Returns a pointer to a location holding the address of last allocated
3736 // byte in the given arena plus 1.
38- // This address is 0 if nothing has been allocated ever in that arena.
39- char **arena_end_ptr () { return &allocation_ptr; }
40-
41- // return the total number of allocatable bytes currently in the arena in its
42- // active semispace.
43- size_t arena_size () const {
44- update_num_blocks ();
45- return BLOCK_SIZE * std::max (num_blocks, num_collection_blocks);
46- }
37+ // This address is nullptr if nothing has been allocated ever in that arena.
38+ char *arena_end_ptr () { return allocation_ptr; }
4739
4840 // Clears the current allocation space by setting its start back to its first
4941 // block. It is used during garbage collection to effectively collect all of the
50- // arena.
42+ // arena. Resets the tripwire.
5143 void arena_clear ();
5244
53- // Resizes the last allocation as long as the resize does not require a new
54- // block allocation.
55- // Returns the address of the byte following the last newlly allocated byte.
45+ // Resizes the last allocation.
46+ // Returns the address of the byte following the last newly allocated byte.
5647 void *arena_resize_last_alloc (ssize_t increase) {
5748 return (allocation_ptr += increase);
5849 }
@@ -71,10 +62,8 @@ class arena {
7162 void arena_swap_and_clear ();
7263
7364 // Given two pointers to objects allocated in the same arena, return the number
74- // of bytes they are separated by within the virtual block of memory represented
75- // by the blocks of that arena. This difference will include blocks containing
76- // sentinel bytes. Undefined behavior will result if the pointers belong to
77- // different arenas.
65+ // of bytes they are apart. Undefined behavior will result if the pointers
66+ // don't belong to the same arena
7867 static ssize_t ptr_diff (char *ptr1, char *ptr2) { return ptr1 - ptr2; }
7968
8069 // Given a starting pointer to an address allocated in an arena and a size in
@@ -84,11 +73,11 @@ class arena {
8473 // 1st argument: the starting pointer
8574 // 2nd argument: the size in bytes to add to the starting pointer
8675 // 3rd argument: the address of last allocated byte in the arena plus 1
87- // Return value: the address allocated in the arena after size bytes from the
88- // starting pointer, or 0 if this is equal to the 3rd argument.
89- static char *move_ptr (char *ptr, size_t size, char const *arena_end_ptr ) {
76+ // Return value: starting pointer + size unless this points to unallocated space
77+ // in which case nullptr is returned
78+ static char *move_ptr (char *ptr, size_t size, char const *end_ptr ) {
9079 char *next_ptr = ptr + size;
91- return (next_ptr == arena_end_ptr ) ? 0 : next_ptr;
80+ return (next_ptr == end_ptr ) ? nullptr : next_ptr;
9281 }
9382
9483 // Returns the ID of the semispace where the given address was allocated.
@@ -97,15 +86,6 @@ class arena {
9786 static char get_arena_semispace_id_of_object (void *ptr);
9887
9988private:
100- union memory_block_header {
101- //
102- // Currently the header just holds the semispace id. But we need it to be a
103- // multiple of sizeof(char*) for alignment purposes so we add a dummy char*.
104- //
105- char semispace;
106- char *alignment_dummy;
107- };
108-
10989 //
11090 // We update the number of 1MB blocks actually written to, only when we need this value,
11191 // or before a garbage collection rather than trying to determine when we write to a fresh block.
@@ -121,13 +101,6 @@ class arena {
121101 }
122102
123103 void initialize_semispace ();
124-
125- static memory_block_header *mem_block_header (void *ptr) {
126- uintptr_t address = reinterpret_cast <uintptr_t >(ptr);
127- return reinterpret_cast <arena::memory_block_header *>(
128- (address - 1 ) & ~(HYPERBLOCK_SIZE - 1 ));
129- }
130-
131104 //
132105 // Current semispace where allocations are being made.
133106 //
@@ -146,9 +119,22 @@ class arena {
146119 = 0 ; // notional number of BLOCK_SIZE blocks in collection semispace
147120};
148121
122+ inline char arena::get_arena_semispace_id_of_object (void *ptr) {
123+ //
124+ // We don't have to deal with the "1 past the end of block" case because
125+ // a valid pointer will always point into our hyperblock - we will never return
126+ // an allocation anywhere near the end of our hyperblock.
127+ //
128+ // Set the low bits to 1 to get the address of the last byte in the hyperblock.
129+ //
130+ uintptr_t end_address
131+ = reinterpret_cast <uintptr_t >(ptr) | (HYPERBLOCK_SIZE - 1 );
132+ return *reinterpret_cast <char *>(end_address);
133+ }
134+
149135// Macro to define a new arena with the given ID. Supports IDs ranging from 0 to
150136// 127.
151- #define REGISTER_ARENA (name, id ) static thread_local arena name (id)
137+ #define REGISTER_ARENA (name, id ) thread_local arena name (id)
152138
153139#ifdef __MACH__
154140//
@@ -169,8 +155,11 @@ inline void *arena::kore_arena_alloc(size_t requested) {
169155 // collect when allowed.
170156 //
171157 time_for_collection = true ;
172- tripwire = current_addr_ptr
173- + HYPERBLOCK_SIZE; // won't trigger again until arena swap
158+ //
159+ // We move the tripwire to 1 past the end of our hyperblock so that we have
160+ // a well defined comparison that will always be false until the next arena swap.
161+ //
162+ tripwire = current_addr_ptr + HYPERBLOCK_SIZE;
174163 }
175164 void *result = allocation_ptr;
176165 allocation_ptr += requested;
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