Initial revision

gc/nursery.c

@@ -0,0 +1,175 @@
+/* 
+ * Copyright (c) 1999 by Silicon Graphics.  All rights reserved.
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program
+ * for any purpose,  provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is granted,
+ * provided the above notices are retained, and a notice that the code was
+ * modified is included with the above copyright notice.
+ */
+
+
+??? This implementation is incomplete.  If you are trying to
+??? compile this you are doing something wrong.
+
+#include "nursery.h"
+
+struct copy_obj {
+    ptr_t forward;	/* Forwarding link for copied objects.	*/
+    GC_copy_descriptor descr; /* Object descriptor	*/
+    word data[1];
+}
+
+ptr_t GC_nursery_start;	/* Start of nursery area.	*/
+			/* Must be NURSERY_BLOCK_SIZE	*/
+			/* aligned.			*/
+ptr_t GC_nursery_end;	/* End of nursery area.		*/
+unsigned char * GC_nursery_map;
+			/* GC_nursery_map[i] != 0 if an object	*/
+			/* starts on the ith 64-bit "word" of 	*/
+			/* nursery.  This simple structure has	*/
+			/* the advantage that 			*/
+			/* allocation is cheap.  Lookup is 	*/
+			/* cheap for pointers to the head of	*/
+			/* an object, which should be the	*/
+			/* usual case.				*/
+#   define NURSERY_MAP_NOT_START	0  /* Not start of object. */
+#   define NURSERY_MAP_START		1  /* Start of object.	   */
+#   define NURSERY_MAP_PINNED		2  /* Start of pinned obj. */
+
+# ifdef ALIGN_DOUBLE
+#   define NURSERY_WORD_SIZE (2 * sizeof(word))
+# else
+#   define NURSERY_WORD_SIZE sizeof(word)
+# endif
+
+# define NURSERY_BLOCK_SIZE (HBLKSIZE/2)	
+	/* HBLKSIZE must be a multiple of NURSERY_BLOCK_SIZE */
+# define NURSERY_SIZE (1024 * NURSERY_BLOCK_SIZE)
+
+size_t GC_nursery_size = NURSERY_SIZE;
+			/* Must be multiple of NURSERY_BLOCK_SIZE	*/
+
+size_t GC_nursery_blocks; /* Number of blocks in the nursery.	*/
+
+unsigned GC_next_nursery_block; /* index of next block we will attempt 	*/
+				/* allocate from during this cycle.	*/
+				/* If it is pinned, we won't actually	*/
+				/* use it.				*/
+
+unsigned short *GC_pinned;	/* Number of pinned objects in ith	*/
+				/* nursery block.			*/
+				/* GC_pinned[i] != 0 if the ith nursery */
+				/* block is pinned, and thus not used	*/
+				/* for allocation.			*/
+
+GC_copy_alloc_state global_alloc_state = (ptr_t)(-1);	/* will overflow. */
+
+/* Should be called with allocator lock held.	*/
+GC_nursery_init() {
+    GC_nursery_start = GET_MEM(GC_nursery_size);
+    GC_nursery_end = GC_nursery_start + GC_nursery_size;
+    GC_next_nursery_block = 0;
+    if (GC_nursery_start < GC_least_plausible_heap_addr) { 
+        GC_least_plausible_heap_addr = GC_nursery_start;   
+    }
+    if (GC_nursery_end > GC_greatest_plausible_heap_addr) {
+        GC_greatest_plausible_heap_addr = GC_nursery_end;  
+    }
+    if (GC_nursery_start & (NURSERY_BLOCK_SIZE-1)) {
+	GC_err_printf1("Nursery area is misaligned!!");
+	/* This should be impossible, since GET_MEM returns HBLKSIZE */
+	/* aligned chunks, and that should be a multiple of 	     */
+	/* NURSERY_BLOCK_SIZE					     */
+	ABORT("misaligned nursery");
+    }
+    GC_nursery_map = GET_MEM(GC_nursery_size/NURSERY_WORD_SIZE);
+    /* Map is cleared a block at a time when we allocate from the block. */
+    /* BZERO(GC_nursery_map, GC_nursery_size/NURSERY_WORD_SIZE);	 */
+    GC_nursery_blocks = GC_nursery_size/NURSERY_BLOCK_SIZE;
+    GC_pinned = GC_scratch_alloc(GC_nursery_blocks * sizeof(unsigned short));
+    BZERO(GC_pinned, GC_nursery_blocks);
+}
+
+/* Pin all nursery objects referenced from mark stack. */
+void GC_pin_mark_stack_objects(void) {
+    for each possible pointer current in a mark stack object
+	if (current >= GC_nursery_start && current < GC_nursery_end) {
+	    unsigned offset = current - GC_nursery_start;
+	    unsigned word_offset = BYTES_TO_WORDS(offset);
+	    unsigned blockno = (current - GC_nursery_start)/NURSERY_BLOCK_SIZE;
+	    while (GC_nursery_map[word_offset] == NURSERY_MAP_NOT_START) {
+		--word_offset;    
+	    }
+	    if (GC_nursery_map[word_offset] != NURSERY_MAP_PINNED) {
+	        GC_nursery_map[word_offset] = NURSERY_MAP_PINNED;
+	        ++GC_pinned[blockno];
+	        ??Push object at GC_nursery_start + WORDS_TO_BYTES(word_offset)
+	        ??onto stack. 
+	    }
+	}
+    }
+}
+
+/* Caller holds allocation lock.	*/
+void GC_collect_nursery(void) {
+    int i;
+    ptr_t scan_ptr = 0;
+    ?? old_mark_stack_top;
+    STOP_WORLD;
+    for (i = 0; i < GC_nursery_blocks; ++i) GC_pinned[i] = 0;
+    GC_push_all_roots();
+    old_mark_stack_top = GC_mark_stack_top();
+    GC_pin_mark_stack_objects();
+    START_WORLD;
+}
+
+/* Initialize an allocation state so that it can be used for 	*/
+/* allocation.  This implicitly reserves a small section of the	*/
+/* nursery for use with his allocator.				*/
+void GC_init_copy_alloc_state(GC_copy_alloc_state *)
+    unsigned next_block;
+    ptr_t block_addr;
+    LOCK();
+    next_block = GC_next_nursery_block;
+    while(is_pinned[next_block] && next_block < GC_nursery_blocks) {
+	++next_block;
+    }
+    if (next_block < GC_nursery_blocks) {
+	block_addr = GC_nursery_start + NURSERY_BLOCK_SIZE * next_block;
+   	GC_next_nursery_block = next_block + 1;
+	BZERO(GC_nursery_map + next_block *
+				(NURSERY_BLOCK_SIZE/NURSERY_WORD_SIZE),
+	      NURSERY_BLOCK_SIZE/NURSERY_WORD_SIZE);
+	*GC_copy_alloc_state = block_addr;
+	UNLOCK();
+    } else {
+     	GC_collect_nursery();
+    	GC_next_nursery_block = 0;
+    	UNLOCK();
+    	get_new_block(s);
+    }
+}
+
+GC_PTR GC_copying_malloc2(GC_copy_descriptor *d, GC_copy_alloc_state *s) {
+    size_t sz = GC_SIZE_FROM_DESCRIPTOR(d);
+    ptrdiff_t offset;
+    ptr_t result = *s;
+    ptr_t new = result + sz;
+    if (new & COPY_BLOCK_MASK <= result & COPY_BLOCK_MASK> {
+	GC_init_copy_alloc_state(s);
+	result = *s;
+	new = result + sz;
+        GC_ASSERT(new & COPY_BLOCK_MASK > result & COPY_BLOCK_MASK>
+    }
+    (struct copy_obj *)result -> descr = d;      
+    (struct copy_obj *)result -> forward = 0;      
+    offset = (result - GC_nursery_start)/NURSERY_WORD_SIZE;
+    GC_nursery_map[offset] = NURSERY_MAP_NOT_START;
+}
+
+GC_PTR GC_copying_malloc(GC_copy_descriptor *d) {
+}