/* -----------------------------------------------------------------------------
- * $Id: MBlock.h,v 1.7 2000/12/04 12:31:21 simonmar Exp $
*
- * (c) The GHC Team, 1998-1999
+ * (c) The GHC Team, 1998-2005
*
* MegaBlock Allocator interface.
*
* ---------------------------------------------------------------------------*/
-extern lnat mblocks_allocated;
+#ifndef MBLOCK_H
+#define MBLOCK_H
-#ifdef ENABLE_WIN32_DLL_SUPPORT
-extern int is_heap_alloced(const void* p);
-#endif
+extern lnat RTS_VAR(mblocks_allocated);
extern void * getMBlock(void);
extern void * getMBlocks(nat n);
+extern void freeAllMBlocks(void);
-#if freebsd2_TARGET_OS || freebsd_TARGET_OS
-/* Executable is loaded from 0x0
- * Shared libraries are loaded at 0x2000000
- * Stack is at the top of the address space. The kernel probably owns
- * 0x8000000 onwards, so we'll pick 0x5000000.
- */
-#define HEAP_BASE 0x50000000
-
-#elif netbsd_TARGET_OS
-/* NetBSD i386 shared libs are at 0x40000000
- */
-#define HEAP_BASE 0x50000000
-#elif openbsd_TARGET_OS
-#define HEAP_BASE 0x50000000
-#elif linux_TARGET_OS
-/* Any ideas?
- */
-#define HEAP_BASE 0x50000000
-
-#elif solaris2_TARGET_OS
-/* guess */
-#define HEAP_BASE 0x50000000
-
-#elif osf3_TARGET_OS
-/* guess */
-#define HEAP_BASE 0x50000000
-
-#elif hpux_TARGET_OS
-/* guess */
-#define HEAP_BASE 0x50000000
-
-#elif _WIN32
-/* doesn't matter, we use a reserve/commit algorithm */
+#if osf3_HOST_OS
+/* ToDo: Perhaps by adjusting this value we can make linking without
+ * -static work (i.e., not generate a core-dumping executable)? */
+#if SIZEOF_VOID_P == 8
+#define HEAP_BASE 0x180000000L
+#else
+#error I have no idea where to begin the heap on a non-64-bit osf3 machine.
+#endif
#else
-#error Dont know where to get memory from on this architecture
-/* ToDo: memory locations on other architectures */
+
+// we're using the generic method
+#define HEAP_BASE 0
+
#endif
+
+/* -----------------------------------------------------------------------------
+ The HEAP_ALLOCED() test.
+
+ HEAP_ALLOCED is called FOR EVERY SINGLE CLOSURE during GC.
+ It needs to be FAST.
+
+ Implementation of HEAP_ALLOCED
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ Since heap is allocated in chunks of megablocks (MBLOCK_SIZE), we
+ can just use a table to record which megablocks in the address
+ space belong to the heap. On a 32-bit machine, with 1Mb
+ megablocks, using 8 bits for each entry in the table, the table
+ requires 4k. Lookups during GC will be fast, because the table
+ will be quickly cached (indeed, performance measurements showed no
+ measurable difference between doing the table lookup and using a
+ constant comparison).
+
+ On 64-bit machines, we cache one 12-bit block map that describes
+ 4096 megablocks or 4GB of memory. If HEAP_ALLOCED is called for
+ an address that is not in the cache, it calls slowIsHeapAlloced
+ (see MBlock.c) which will find the block map for the 4GB block in
+ question.
+ -------------------------------------------------------------------------- */
+
+#if SIZEOF_VOID_P == 4
+extern StgWord8 mblock_map[];
+
+/* On a 32-bit machine a 4KB table is always sufficient */
+# define MBLOCK_MAP_SIZE 4096
+# define MBLOCK_MAP_ENTRY(p) ((StgWord)(p) >> MBLOCK_SHIFT)
+# define HEAP_ALLOCED(p) mblock_map[MBLOCK_MAP_ENTRY(p)]
+
+#elif SIZEOF_VOID_P == 8
+
+# define MBLOCK_MAP_SIZE 4096
+# define MBLOCK_MAP_ENTRY(p) (((StgWord)(p) & 0xffffffff) >> MBLOCK_SHIFT)
+
+typedef struct {
+ StgWord32 addrHigh32;
+ StgWord8 mblocks[MBLOCK_MAP_SIZE];
+} MBlockMap;
+
+extern MBlockMap *mblock_cache;
+
+StgBool slowIsHeapAlloced(void *p);
+
+# define HEAP_ALLOCED(p) \
+ ( ((((StgWord)(p)) >> 32) == mblock_cache->addrHigh32) \
+ ? mblock_cache->mblocks[MBLOCK_MAP_ENTRY(p)] \
+ : slowIsHeapAlloced(p) )
+
+#else
+# error HEAP_ALLOCED not defined
+#endif
+
+#endif /* MBLOCK_H */