Initial revision

1 files changed, 814 insertions, 0 deletions

diff --git a/gc/typd_mlc.c b/gc/typd_mlc.c
new file mode 100644
index 0000000..74f455d
--- /dev/null
+++ b/gc/typd_mlc.c
@@ -0,0 +1,814 @@
+/*
+ * Copyright (c) 1991-1994 by Xerox Corporation.  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.
+ *
+ */
+/* Boehm, July 31, 1995 5:02 pm PDT */
+
+
+/*
+ * Some simple primitives for allocation with explicit type information.
+ * Simple objects are allocated such that they contain a GC_descr at the
+ * end (in the last allocated word).  This descriptor may be a procedure
+ * which then examines an extended descriptor passed as its environment.
+ *
+ * Arrays are treated as simple objects if they have sufficiently simple
+ * structure.  Otherwise they are allocated from an array kind that supplies
+ * a special mark procedure.  These arrays contain a pointer to a
+ * complex_descriptor as their last word.
+ * This is done because the environment field is too small, and the collector
+ * must trace the complex_descriptor.
+ *
+ * Note that descriptors inside objects may appear cleared, if we encounter a
+ * false refrence to an object on a free list.  In the GC_descr case, this
+ * is OK, since a 0 descriptor corresponds to examining no fields.
+ * In the complex_descriptor case, we explicitly check for that case.
+ *
+ * MAJOR PARTS OF THIS CODE HAVE NOT BEEN TESTED AT ALL and are not testable,
+ * since they are not accessible through the current interface.
+ */
+
+#include "gc_priv.h"
+#include "gc_mark.h"
+#include "gc_typed.h"
+
+# ifdef ADD_BYTE_AT_END
+#   define EXTRA_BYTES (sizeof(word) - 1)
+# else
+#   define EXTRA_BYTES (sizeof(word))
+# endif
+
+GC_bool GC_explicit_typing_initialized = FALSE;
+
+int GC_explicit_kind;	/* Object kind for objects with indirect	*/
+			/* (possibly extended) descriptors.		*/
+
+int GC_array_kind;	/* Object kind for objects with complex		*/
+			/* descriptors and GC_array_mark_proc.		*/
+
+/* Extended descriptors.  GC_typed_mark_proc understands these.	*/
+/* These are used for simple objects that are larger than what	*/
+/* can be described by a BITMAP_BITS sized bitmap.		*/
+typedef struct {
+	word ed_bitmap;	/* lsb corresponds to first word.	*/
+	GC_bool ed_continued;	/* next entry is continuation.	*/
+} ext_descr;
+
+/* Array descriptors.  GC_array_mark_proc understands these.	*/
+/* We may eventually need to add provisions for headers and	*/
+/* trailers.  Hence we provide for tree structured descriptors, */
+/* though we don't really use them currently.			*/
+typedef union ComplexDescriptor {
+    struct LeafDescriptor {	/* Describes simple array	*/
+        word ld_tag;
+#	define LEAF_TAG 1
+	word ld_size;		/* bytes per element	*/
+				/* multiple of ALIGNMENT	*/
+	word ld_nelements;	/* Number of elements.	*/
+	GC_descr ld_descriptor; /* A simple length, bitmap,	*/
+				/* or procedure descriptor.	*/
+    } ld;
+    struct ComplexArrayDescriptor {
+        word ad_tag;
+#	define ARRAY_TAG 2
+	word ad_nelements;
+	union ComplexDescriptor * ad_element_descr;
+    } ad;
+    struct SequenceDescriptor {
+        word sd_tag;
+#	define SEQUENCE_TAG 3
+	union ComplexDescriptor * sd_first;
+	union ComplexDescriptor * sd_second;
+    } sd;
+} complex_descriptor;
+#define TAG ld.ld_tag
+
+ext_descr * GC_ext_descriptors;	/* Points to array of extended 	*/
+				/* descriptors.			*/
+
+word GC_ed_size = 0;	/* Current size of above arrays.	*/
+# define ED_INITIAL_SIZE 100;
+
+word GC_avail_descr = 0;	/* Next available slot.		*/
+
+int GC_typed_mark_proc_index;	/* Indices of my mark		*/
+int GC_array_mark_proc_index;	/* procedures.			*/
+
+/* Add a multiword bitmap to GC_ext_descriptors arrays.  Return	*/
+/* starting index.						*/
+/* Returns -1 on failure.					*/
+/* Caller does not hold allocation lock.			*/
+signed_word GC_add_ext_descriptor(bm, nbits)
+GC_bitmap bm;
+word nbits;
+{
+    register size_t nwords = divWORDSZ(nbits + WORDSZ-1);
+    register signed_word result;
+    register word i;
+    register word last_part;
+    register int extra_bits;
+    DCL_LOCK_STATE;
+
+    DISABLE_SIGNALS();
+    LOCK();
+    while (GC_avail_descr + nwords >= GC_ed_size) {
+    	ext_descr * new;
+    	size_t new_size;
+    	word ed_size = GC_ed_size;
+    	
+    	UNLOCK();
+        ENABLE_SIGNALS();
+    	if (ed_size == 0) {
+    	    new_size = ED_INITIAL_SIZE;
+    	} else {
+    	    new_size = 2 * ed_size;
+    	    if (new_size > MAX_ENV) return(-1);
+    	} 
+    	new = (ext_descr *) GC_malloc_atomic(new_size * sizeof(ext_descr));
+    	if (new == 0) return(-1);
+    	DISABLE_SIGNALS();
+        LOCK();
+        if (ed_size == GC_ed_size) {
+            if (GC_avail_descr != 0) {
+    	        BCOPY(GC_ext_descriptors, new,
+    	              GC_avail_descr * sizeof(ext_descr));
+    	    }
+    	    GC_ed_size = new_size;
+    	    GC_ext_descriptors = new;
+    	}  /* else another thread already resized it in the meantime */
+    }
+    result = GC_avail_descr;
+    for (i = 0; i < nwords-1; i++) {
+        GC_ext_descriptors[result + i].ed_bitmap = bm[i];
+        GC_ext_descriptors[result + i].ed_continued = TRUE;
+    }
+    last_part = bm[i];
+    /* Clear irrelevant bits. */
+    extra_bits = nwords * WORDSZ - nbits;
+    last_part <<= extra_bits;
+    last_part >>= extra_bits;
+    GC_ext_descriptors[result + i].ed_bitmap = last_part;
+    GC_ext_descriptors[result + i].ed_continued = FALSE;
+    GC_avail_descr += nwords;
+    UNLOCK();
+    ENABLE_SIGNALS();
+    return(result);
+}
+
+/* Table of bitmap descriptors for n word long all pointer objects.	*/
+GC_descr GC_bm_table[WORDSZ/2];
+	
+/* Return a descriptor for the concatenation of 2 nwords long objects,	*/
+/* each of which is described by descriptor.				*/
+/* The result is known to be short enough to fit into a bitmap		*/
+/* descriptor.								*/
+/* Descriptor is a DS_LENGTH or DS_BITMAP descriptor.			*/
+GC_descr GC_double_descr(descriptor, nwords)
+register GC_descr descriptor;
+register word nwords;
+{
+    if (descriptor && DS_TAGS == DS_LENGTH) {
+        descriptor = GC_bm_table[BYTES_TO_WORDS((word)descriptor)];
+    };
+    descriptor |= (descriptor & ~DS_TAGS) >> nwords;
+    return(descriptor);
+}
+
+complex_descriptor * GC_make_sequence_descriptor();
+
+/* Build a descriptor for an array with nelements elements,	*/
+/* each of which can be described by a simple descriptor.	*/
+/* We try to optimize some common cases.			*/
+/* If the result is COMPLEX, then a complex_descr* is returned  */
+/* in *complex_d.							*/
+/* If the result is LEAF, then we built a LeafDescriptor in	*/
+/* the structure pointed to by leaf.				*/
+/* The tag in the leaf structure is not set.			*/
+/* If the result is SIMPLE, then a GC_descr			*/
+/* is returned in *simple_d.					*/
+/* If the result is NO_MEM, then				*/
+/* we failed to allocate the descriptor.			*/
+/* The implementation knows that DS_LENGTH is 0.		*/
+/* *leaf, *complex_d, and *simple_d may be used as temporaries	*/
+/* during the construction.					*/
+# define COMPLEX 2
+# define LEAF 1
+# define SIMPLE 0
+# define NO_MEM (-1)
+int GC_make_array_descriptor(nelements, size, descriptor,
+			     simple_d, complex_d, leaf)
+word size;
+word nelements;
+GC_descr descriptor;
+GC_descr *simple_d;
+complex_descriptor **complex_d;
+struct LeafDescriptor * leaf;
+{
+#   define OPT_THRESHOLD 50
+	/* For larger arrays, we try to combine descriptors of adjacent	*/
+	/* descriptors to speed up marking, and to reduce the amount	*/
+	/* of space needed on the mark stack.				*/
+    if ((descriptor & DS_TAGS) == DS_LENGTH) {
+      if ((word)descriptor == size) {
+    	*simple_d = nelements * descriptor;
+    	return(SIMPLE);
+      } else if ((word)descriptor == 0) {
+        *simple_d = (GC_descr)0;
+        return(SIMPLE);
+      }
+    }
+    if (nelements <= OPT_THRESHOLD) {
+      if (nelements <= 1) {
+        if (nelements == 1) {
+            *simple_d = descriptor;
+            return(SIMPLE);
+        } else {
+            *simple_d = (GC_descr)0;
+            return(SIMPLE);
+        }
+      }
+    } else if (size <= BITMAP_BITS/2
+    	       && (descriptor & DS_TAGS) != DS_PROC
+    	       && (size & (sizeof(word)-1)) == 0) {
+      int result =      
+          GC_make_array_descriptor(nelements/2, 2*size,
+      				   GC_double_descr(descriptor,
+      				   		   BYTES_TO_WORDS(size)),
+      				   simple_d, complex_d, leaf);
+      if ((nelements & 1) == 0) {
+          return(result);
+      } else {
+          struct LeafDescriptor * one_element =
+              (struct LeafDescriptor *)
+        	GC_malloc_atomic(sizeof(struct LeafDescriptor));
+          
+          if (result == NO_MEM || one_element == 0) return(NO_MEM);
+          one_element -> ld_tag = LEAF_TAG;
+          one_element -> ld_size = size;
+          one_element -> ld_nelements = 1;
+          one_element -> ld_descriptor = descriptor;
+          switch(result) {
+            case SIMPLE:
+            {
+              struct LeafDescriptor * beginning =
+                (struct LeafDescriptor *)
+        	  GC_malloc_atomic(sizeof(struct LeafDescriptor));
+              if (beginning == 0) return(NO_MEM);
+              beginning -> ld_tag = LEAF_TAG;
+              beginning -> ld_size = size;
+              beginning -> ld_nelements = 1;
+              beginning -> ld_descriptor = *simple_d;
+              *complex_d = GC_make_sequence_descriptor(
+              			(complex_descriptor *)beginning,
+              			(complex_descriptor *)one_element);
+              break;
+            }
+            case LEAF:
+            {
+              struct LeafDescriptor * beginning =
+                (struct LeafDescriptor *)
+        	  GC_malloc_atomic(sizeof(struct LeafDescriptor));
+              if (beginning == 0) return(NO_MEM);
+              beginning -> ld_tag = LEAF_TAG;
+              beginning -> ld_size = leaf -> ld_size;
+              beginning -> ld_nelements = leaf -> ld_nelements;
+              beginning -> ld_descriptor = leaf -> ld_descriptor;
+              *complex_d = GC_make_sequence_descriptor(
+              			(complex_descriptor *)beginning,
+              			(complex_descriptor *)one_element);
+              break;
+            }
+            case COMPLEX:
+              *complex_d = GC_make_sequence_descriptor(
+              			*complex_d,
+              			(complex_descriptor *)one_element);
+              break;
+          }
+          return(COMPLEX);
+      }
+    }
+    {
+        leaf -> ld_size = size;
+        leaf -> ld_nelements = nelements;
+        leaf -> ld_descriptor = descriptor;
+        return(LEAF);
+    }
+}
+
+complex_descriptor * GC_make_sequence_descriptor(first, second)
+complex_descriptor * first;
+complex_descriptor * second;
+{
+    struct SequenceDescriptor * result =
+        (struct SequenceDescriptor *)
+        	GC_malloc(sizeof(struct SequenceDescriptor));
+    /* Can't result in overly conservative marking, since tags are	*/
+    /* very small integers. Probably faster than maintaining type	*/
+    /* info.								*/    
+    if (result != 0) {
+    	result -> sd_tag = SEQUENCE_TAG;
+        result -> sd_first = first;
+        result -> sd_second = second;
+    }
+    return((complex_descriptor *)result);
+}
+
+#ifdef UNDEFINED
+complex_descriptor * GC_make_complex_array_descriptor(nelements, descr)
+word nelements;
+complex_descriptor * descr;
+{
+    struct ComplexArrayDescriptor * result =
+        (struct ComplexArrayDescriptor *)
+        	GC_malloc(sizeof(struct ComplexArrayDescriptor));
+    
+    if (result != 0) {
+    	result -> ad_tag = ARRAY_TAG;
+        result -> ad_nelements = nelements;
+        result -> ad_element_descr = descr;
+    }
+    return((complex_descriptor *)result);
+}
+#endif
+
+ptr_t * GC_eobjfreelist;
+
+ptr_t * GC_arobjfreelist;
+
+mse * GC_typed_mark_proc();
+
+mse * GC_array_mark_proc();
+
+GC_descr GC_generic_array_descr;
+
+/* Caller does not hold allocation lock. */
+void GC_init_explicit_typing()
+{
+    register int i;
+    DCL_LOCK_STATE;
+
+    
+#   ifdef PRINTSTATS
+     	if (sizeof(struct LeafDescriptor) % sizeof(word) != 0)
+     	    ABORT("Bad leaf descriptor size");
+#   endif
+    DISABLE_SIGNALS();
+    LOCK();
+    if (GC_explicit_typing_initialized) {
+      UNLOCK();
+      ENABLE_SIGNALS();
+      return;
+    }
+    GC_explicit_typing_initialized = TRUE;
+    /* Set up object kind with simple indirect descriptor. */
+      GC_eobjfreelist = (ptr_t *)
+          GC_generic_malloc_inner((MAXOBJSZ+1)*sizeof(ptr_t), PTRFREE);
+      if (GC_eobjfreelist == 0) ABORT("Couldn't allocate GC_eobjfreelist");
+      BZERO(GC_eobjfreelist, (MAXOBJSZ+1)*sizeof(ptr_t));
+      GC_explicit_kind = GC_n_kinds++;
+      GC_obj_kinds[GC_explicit_kind].ok_freelist = GC_eobjfreelist;
+      GC_obj_kinds[GC_explicit_kind].ok_reclaim_list = 0;
+      GC_obj_kinds[GC_explicit_kind].ok_descriptor =
+    		(((word)WORDS_TO_BYTES(-1)) | DS_PER_OBJECT);
+      GC_obj_kinds[GC_explicit_kind].ok_relocate_descr = TRUE;
+      GC_obj_kinds[GC_explicit_kind].ok_init = TRUE;
+    		/* Descriptors are in the last word of the object. */
+      GC_typed_mark_proc_index = GC_n_mark_procs;
+      GC_mark_procs[GC_typed_mark_proc_index] = GC_typed_mark_proc;
+      GC_n_mark_procs++;
+        /* Moving this up breaks DEC AXP compiler.      */
+    /* Set up object kind with array descriptor. */
+      GC_arobjfreelist = (ptr_t *)
+          GC_generic_malloc_inner((MAXOBJSZ+1)*sizeof(ptr_t), PTRFREE);
+      if (GC_arobjfreelist == 0) ABORT("Couldn't allocate GC_arobjfreelist");
+      BZERO(GC_arobjfreelist, (MAXOBJSZ+1)*sizeof(ptr_t));
+      if (GC_n_mark_procs >= MAX_MARK_PROCS)
+      		ABORT("No slot for array mark proc");
+      GC_array_mark_proc_index = GC_n_mark_procs++;
+      if (GC_n_kinds >= MAXOBJKINDS)
+      		ABORT("No kind available for array objects");
+      GC_array_kind = GC_n_kinds++;
+      GC_obj_kinds[GC_array_kind].ok_freelist = GC_arobjfreelist;
+      GC_obj_kinds[GC_array_kind].ok_reclaim_list = 0;
+      GC_obj_kinds[GC_array_kind].ok_descriptor =
+    		MAKE_PROC(GC_array_mark_proc_index, 0);;
+      GC_obj_kinds[GC_array_kind].ok_relocate_descr = FALSE;
+      GC_obj_kinds[GC_array_kind].ok_init = TRUE;
+    		/* Descriptors are in the last word of the object. */
+            GC_mark_procs[GC_array_mark_proc_index] = GC_array_mark_proc;
+      for (i = 0; i < WORDSZ/2; i++) {
+          GC_descr d = (((word)(-1)) >> (WORDSZ - i)) << (WORDSZ - i);
+          d |= DS_BITMAP;
+          GC_bm_table[i] = d;
+      }
+      GC_generic_array_descr = MAKE_PROC(GC_array_mark_proc_index, 0); 
+    UNLOCK();
+    ENABLE_SIGNALS();
+}
+
+mse * GC_typed_mark_proc(addr, mark_stack_ptr, mark_stack_limit, env)
+register word * addr;
+register mse * mark_stack_ptr;
+mse * mark_stack_limit;
+word env;
+{
+    register word bm = GC_ext_descriptors[env].ed_bitmap;
+    register word * current_p = addr;
+    register word current;
+    register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
+    register ptr_t least_ha = GC_least_plausible_heap_addr;
+    
+    for (; bm != 0; bm >>= 1, current_p++) {
+    	if (bm & 1) {
+    	    current = *current_p;
+    	    if ((ptr_t)current >= least_ha && (ptr_t)current <= greatest_ha) {
+    	        PUSH_CONTENTS(current, mark_stack_ptr,
+			      mark_stack_limit, current_p, exit1);
+    	    }
+    	}
+    }
+    if (GC_ext_descriptors[env].ed_continued) {
+        /* Push an entry with the rest of the descriptor back onto the	*/
+        /* stack.  Thus we never do too much work at once.  Note that	*/
+        /* we also can't overflow the mark stack unless we actually 	*/
+        /* mark something.						*/
+        mark_stack_ptr++;
+        if (mark_stack_ptr >= mark_stack_limit) {
+            mark_stack_ptr = GC_signal_mark_stack_overflow(mark_stack_ptr);
+        }
+        mark_stack_ptr -> mse_start = addr + WORDSZ;
+        mark_stack_ptr -> mse_descr =
+        	MAKE_PROC(GC_typed_mark_proc_index, env+1);
+    }
+    return(mark_stack_ptr);
+}
+
+/* Return the size of the object described by d.  It would be faster to	*/
+/* store this directly, or to compute it as part of			*/
+/* GC_push_complex_descriptor, but hopefully it doesn't matter.		*/
+word GC_descr_obj_size(d)
+register complex_descriptor *d;
+{
+    switch(d -> TAG) {
+      case LEAF_TAG:
+      	return(d -> ld.ld_nelements * d -> ld.ld_size);
+      case ARRAY_TAG:
+        return(d -> ad.ad_nelements
+               * GC_descr_obj_size(d -> ad.ad_element_descr));
+      case SEQUENCE_TAG:
+        return(GC_descr_obj_size(d -> sd.sd_first)
+               + GC_descr_obj_size(d -> sd.sd_second));
+      default:
+        ABORT("Bad complex descriptor");
+        /*NOTREACHED*/ return 0; /*NOTREACHED*/
+    }
+}
+
+/* Push descriptors for the object at addr with complex descriptor d	*/
+/* onto the mark stack.  Return 0 if the mark stack overflowed.  	*/
+mse * GC_push_complex_descriptor(addr, d, msp, msl)
+word * addr;
+register complex_descriptor *d;
+register mse * msp;
+mse * msl;
+{
+    register ptr_t current = (ptr_t) addr;
+    register word nelements;
+    register word sz;
+    register word i;
+    
+    switch(d -> TAG) {
+      case LEAF_TAG:
+        {
+          register GC_descr descr = d -> ld.ld_descriptor;
+          
+          nelements = d -> ld.ld_nelements;
+          if (msl - msp <= (ptrdiff_t)nelements) return(0);
+          sz = d -> ld.ld_size;
+          for (i = 0; i < nelements; i++) {
+              msp++;
+              msp -> mse_start = (word *)current;
+              msp -> mse_descr = descr;
+              current += sz;
+          }
+          return(msp);
+        }
+      case ARRAY_TAG:
+        {
+          register complex_descriptor *descr = d -> ad.ad_element_descr;
+          
+          nelements = d -> ad.ad_nelements;
+          sz = GC_descr_obj_size(descr);
+          for (i = 0; i < nelements; i++) {
+              msp = GC_push_complex_descriptor((word *)current, descr,
+              					msp, msl);
+              if (msp == 0) return(0);
+              current += sz;
+          }
+          return(msp);
+        }
+      case SEQUENCE_TAG:
+        {
+          sz = GC_descr_obj_size(d -> sd.sd_first);
+          msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_first,
+          				   msp, msl);
+          if (msp == 0) return(0);
+          current += sz;
+          msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_second,
+          				   msp, msl);
+          return(msp);
+        }
+      default:
+        ABORT("Bad complex descriptor");
+        /*NOTREACHED*/ return 0; /*NOTREACHED*/
+   }
+}
+
+/*ARGSUSED*/
+mse * GC_array_mark_proc(addr, mark_stack_ptr, mark_stack_limit, env)
+register word * addr;
+register mse * mark_stack_ptr;
+mse * mark_stack_limit;
+word env;
+{
+    register hdr * hhdr = HDR(addr);
+    register word sz = hhdr -> hb_sz;
+    register complex_descriptor * descr = (complex_descriptor *)(addr[sz-1]);
+    mse * orig_mark_stack_ptr = mark_stack_ptr;
+    mse * new_mark_stack_ptr;
+    
+    if (descr == 0) {
+    	/* Found a reference to a free list entry.  Ignore it. */
+    	return(orig_mark_stack_ptr);
+    }
+    /* In use counts were already updated when array descriptor was	*/
+    /* pushed.  Here we only replace it by subobject descriptors, so 	*/
+    /* no update is necessary.						*/
+    new_mark_stack_ptr = GC_push_complex_descriptor(addr, descr,
+    						    mark_stack_ptr,
+    						    mark_stack_limit-1);
+    if (new_mark_stack_ptr == 0) {
+    	/* Doesn't fit.  Conservatively push the whole array as a unit	*/
+    	/* and request a mark stack expansion.				*/
+    	/* This cannot cause a mark stack overflow, since it replaces	*/
+    	/* the original array entry.					*/
+    	GC_mark_stack_too_small = TRUE;
+    	new_mark_stack_ptr = orig_mark_stack_ptr + 1;
+    	new_mark_stack_ptr -> mse_start = addr;
+    	new_mark_stack_ptr -> mse_descr = WORDS_TO_BYTES(sz) | DS_LENGTH;
+    } else {
+        /* Push descriptor itself */
+        new_mark_stack_ptr++;
+        new_mark_stack_ptr -> mse_start = addr + sz - 1;
+        new_mark_stack_ptr -> mse_descr = sizeof(word) | DS_LENGTH;
+    }
+    return(new_mark_stack_ptr);
+}
+
+#if defined(__STDC__) || defined(__cplusplus)
+  GC_descr GC_make_descriptor(GC_bitmap bm, size_t len)
+#else
+  GC_descr GC_make_descriptor(bm, len)
+  GC_bitmap bm;
+  size_t len;
+#endif
+{
+    register signed_word last_set_bit = len - 1;
+    register word result;
+    register int i;
+#   define HIGH_BIT (((word)1) << (WORDSZ - 1))
+    
+    if (!GC_explicit_typing_initialized) GC_init_explicit_typing();
+    while (last_set_bit >= 0 && !GC_get_bit(bm, last_set_bit)) last_set_bit --;
+    if (last_set_bit < 0) return(0 /* no pointers */);
+#   if ALIGNMENT == CPP_WORDSZ/8
+    {
+      register GC_bool all_bits_set = TRUE;
+      for (i = 0; i < last_set_bit; i++) {
+    	if (!GC_get_bit(bm, i)) {
+    	    all_bits_set = FALSE;
+    	    break;
+    	}
+      }
+      if (all_bits_set) {
+    	/* An initial section contains all pointers.  Use length descriptor. */
+        return(WORDS_TO_BYTES(last_set_bit+1) | DS_LENGTH);
+      }
+    }
+#   endif
+    if (last_set_bit < BITMAP_BITS) {
+    	/* Hopefully the common case.			*/
+    	/* Build bitmap descriptor (with bits reversed)	*/
+    	result = HIGH_BIT;
+    	for (i = last_set_bit - 1; i >= 0; i--) {
+    	    result >>= 1;
+    	    if (GC_get_bit(bm, i)) result |= HIGH_BIT;
+    	}
+    	result |= DS_BITMAP;
+    	return(result);
+    } else {
+    	signed_word index;
+    	
+    	index = GC_add_ext_descriptor(bm, (word)last_set_bit+1);
+    	if (index == -1) return(WORDS_TO_BYTES(last_set_bit+1) | DS_LENGTH);
+    				/* Out of memory: use conservative	*/
+    				/* approximation.			*/
+    	result = MAKE_PROC(GC_typed_mark_proc_index, (word)index);
+    	return(result);
+    }
+}
+
+ptr_t GC_clear_stack();
+
+#define GENERAL_MALLOC(lb,k) \
+    (GC_PTR)GC_clear_stack(GC_generic_malloc((word)lb, k))
+    
+#define GENERAL_MALLOC_IOP(lb,k) \
+    (GC_PTR)GC_clear_stack(GC_generic_malloc_ignore_off_page(lb, k))
+
+#if defined(__STDC__) || defined(__cplusplus)
+  void * GC_malloc_explicitly_typed(size_t lb, GC_descr d)
+#else
+  char * GC_malloc_explicitly_typed(lb, d)
+  size_t lb;
+  GC_descr d;
+#endif
+{
+register ptr_t op;
+register ptr_t * opp;
+register word lw;
+DCL_LOCK_STATE;
+
+    lb += EXTRA_BYTES;
+    if( SMALL_OBJ(lb) ) {
+#       ifdef MERGE_SIZES
+	  lw = GC_size_map[lb];
+#	else
+	  lw = ALIGNED_WORDS(lb);
+#       endif
+	opp = &(GC_eobjfreelist[lw]);
+	FASTLOCK();
+        if( !FASTLOCK_SUCCEEDED() || (op = *opp) == 0 ) {
+            FASTUNLOCK();
+            op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
+	    if (0 == op) return(0);
+#	    ifdef MERGE_SIZES
+		lw = GC_size_map[lb];	/* May have been uninitialized.	*/            
+#	    endif
+        } else {
+            *opp = obj_link(op);
+            GC_words_allocd += lw;
+            FASTUNLOCK();
+        }
+   } else {
+       op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
+       if (op != NULL)
+	    lw = BYTES_TO_WORDS(GC_size(op));
+   }
+   if (op != NULL)
+       ((word *)op)[lw - 1] = d;
+   return((GC_PTR) op);
+}
+
+#if defined(__STDC__) || defined(__cplusplus)
+  void * GC_malloc_explicitly_typed_ignore_off_page(size_t lb, GC_descr d)
+#else
+  char * GC_malloc_explicitly_typed_ignore_off_page(lb, d)
+  size_t lb;
+  GC_descr d;
+#endif
+{
+register ptr_t op;
+register ptr_t * opp;
+register word lw;
+DCL_LOCK_STATE;
+
+    lb += EXTRA_BYTES;
+    if( SMALL_OBJ(lb) ) {
+#       ifdef MERGE_SIZES
+	  lw = GC_size_map[lb];
+#	else
+	  lw = ALIGNED_WORDS(lb);
+#       endif
+	opp = &(GC_eobjfreelist[lw]);
+	FASTLOCK();
+        if( !FASTLOCK_SUCCEEDED() || (op = *opp) == 0 ) {
+            FASTUNLOCK();
+            op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
+#	    ifdef MERGE_SIZES
+		lw = GC_size_map[lb];	/* May have been uninitialized.	*/            
+#	    endif
+        } else {
+            *opp = obj_link(op);
+            GC_words_allocd += lw;
+            FASTUNLOCK();
+        }
+   } else {
+       op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
+       if (op != NULL)
+       lw = BYTES_TO_WORDS(GC_size(op));
+   }
+   if (op != NULL)
+   ((word *)op)[lw - 1] = d;
+   return((GC_PTR) op);
+}
+
+#if defined(__STDC__) || defined(__cplusplus)
+  void * GC_calloc_explicitly_typed(size_t n,
+  				    size_t lb,
+  				    GC_descr d)
+#else
+  char * GC_calloc_explicitly_typed(n, lb, d)
+  size_t n;
+  size_t lb;
+  GC_descr d;
+#endif
+{
+register ptr_t op;
+register ptr_t * opp;
+register word lw;
+GC_descr simple_descr;
+complex_descriptor *complex_descr;
+register int descr_type;
+struct LeafDescriptor leaf;
+DCL_LOCK_STATE;
+
+    descr_type = GC_make_array_descriptor((word)n, (word)lb, d,
+    					  &simple_descr, &complex_descr, &leaf);
+    switch(descr_type) {
+    	case NO_MEM: return(0);
+    	case SIMPLE: return(GC_malloc_explicitly_typed(n*lb, simple_descr));
+    	case LEAF:
+    	    lb *= n;
+    	    lb += sizeof(struct LeafDescriptor) + EXTRA_BYTES;
+    	    break;
+    	case COMPLEX:
+    	    lb *= n;
+    	    lb += EXTRA_BYTES;
+    	    break;
+    }
+    if( SMALL_OBJ(lb) ) {
+#       ifdef MERGE_SIZES
+	  lw = GC_size_map[lb];
+#	else
+	  lw = ALIGNED_WORDS(lb);
+#       endif
+	opp = &(GC_arobjfreelist[lw]);
+	FASTLOCK();
+        if( !FASTLOCK_SUCCEEDED() || (op = *opp) == 0 ) {
+            FASTUNLOCK();
+            op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
+	    if (0 == op) return(0);
+#	    ifdef MERGE_SIZES
+		lw = GC_size_map[lb];	/* May have been uninitialized.	*/            
+#	    endif
+        } else {
+            *opp = obj_link(op);
+            GC_words_allocd += lw;
+            FASTUNLOCK();
+        }
+   } else {
+       op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
+       if (0 == op) return(0);
+       lw = BYTES_TO_WORDS(GC_size(op));
+   }
+   if (descr_type == LEAF) {
+       /* Set up the descriptor inside the object itself. */
+       VOLATILE struct LeafDescriptor * lp =
+           (struct LeafDescriptor *)
+               ((word *)op
+                + lw - (BYTES_TO_WORDS(sizeof(struct LeafDescriptor)) + 1));
+                
+       lp -> ld_tag = LEAF_TAG;
+       lp -> ld_size = leaf.ld_size;
+       lp -> ld_nelements = leaf.ld_nelements;
+       lp -> ld_descriptor = leaf.ld_descriptor;
+       ((VOLATILE word *)op)[lw - 1] = (word)lp;
+   } else {
+       extern unsigned GC_finalization_failures;
+       unsigned ff = GC_finalization_failures;
+       
+       ((word *)op)[lw - 1] = (word)complex_descr;
+       /* Make sure the descriptor is cleared once there is any danger	*/
+       /* it may have been collected.					*/
+       (void)
+         GC_general_register_disappearing_link((GC_PTR *)
+         					  ((word *)op+lw-1),
+       					          (GC_PTR) op);
+       if (ff != GC_finalization_failures) {
+	   /* Couldn't register it due to lack of memory.  Punt.	*/
+	   /* This will probably fail too, but gives the recovery code  */
+	   /* a chance.							*/
+	   return(GC_malloc(n*lb));
+       }			          
+   }
+   return((GC_PTR) op);
+}