text: /*
   * mini-gc.c: GC interface for the mono JIT
   *
   * Author:
   *   Zoltan Varga (vargaz@gmail.com)
   *
   * Copyright 2009 Novell, Inc (http://www.novell.com)
   * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
   */
  
  #include "config.h"
  #include "mini-gc.h"
  #include <mono/metadata/gc-internal.h>
  
  //#if 0
  #if defined(HAVE_SGEN_GC) && defined(MONO_ARCH_GC_MAPS_SUPPORTED)
  
  #include <mono/metadata/sgen-gc.h>
  #include <mono/metadata/gc-internal.h>
  #include <mono/utils/mono-counters.h>
  
  /* Contains state needed by the GC Map construction code */
  typedef struct {
  	/*
  	 * This contains information about stack slots initialized in the prolog, encoded using
  	 * (slot_index << 16) | slot_type. The slot_index is relative to the CFA, i.e. 0
  	 * means cfa+0, 1 means cfa-4/8, etc.
  	 */
  	GSList *stack_slots_from_cfa;
  	/* Same for stack slots relative to the frame pointer */
  	GSList *stack_slots_from_fp;
  
  	/* Number of slots in the map */
  	int nslots;
  	/* The number of registers in the map */
  	int nregs;
  	/* Min and Max offsets of the stack frame relative to fp */
  	int min_offset, max_offset;
  	/* Same for the locals area */
  	int locals_min_offset, locals_max_offset;
  
  	/* The call sites where this frame can be stopped during GC */
  	GCCallSite **callsites;
  	/* The number of call sites */
  	int ncallsites;
  
  	/*
  	 * The width of the stack bitmaps in bytes. This is not equal to the bitmap width at
       * runtime, since it includes columns which are 0.
  	 */
  	int stack_bitmap_width;
  	/* 
  	 * A bitmap whose width equals nslots, and whose height equals ncallsites.
  	 * The bitmap contains a 1 if the corresponding stack slot has type SLOT_REF at the
  	 * given callsite.
  	 */
  	guint8 *stack_ref_bitmap;
  	/* Same for SLOT_PIN */
  	guint8 *stack_pin_bitmap;
  
  	/*
  	 * Similar bitmaps for registers. These have width MONO_MAX_IREGS in bits.
  	 */
  	int reg_bitmap_width;
  	guint8 *reg_ref_bitmap;
  	guint8 *reg_pin_bitmap;
  } MonoCompileGC;
  
  #define ALIGN_TO(val,align) ((((mgreg_t)val) + ((align) - 1)) & ~((align) - 1))
  
  #undef DEBUG
  
  #if 0
  /* We don't support debug levels, its all-or-nothing */
  #define DEBUG(s) do { s; fflush (logfile); } while (0)
  #define DEBUG_ENABLED 1
  #else
  #define DEBUG(s)
  #endif
  
  #ifdef DEBUG_ENABLED
  //#if 1
  #define DEBUG_PRECISE(s) do { s; } while (0)
  #define DEBUG_PRECISE_ENABLED
  #else
  #define DEBUG_PRECISE(s)
  #endif
  
  /*
   * Contains information collected during the conservative stack marking pass,
   * used during the precise pass. This helps to avoid doing a stack walk twice, which
   * is expensive.
   */
  typedef struct {
  	guint8 *bitmap;
  	int nslots;
      int frame_start_offset;
  	int nreg_locations;
  	/* Relative to stack_start */
  	int reg_locations [MONO_MAX_IREGS];
  #ifdef DEBUG_PRECISE_ENABLED
  	MonoJitInfo *ji;
  	gpointer fp;
  	int regs [MONO_MAX_IREGS];
  #endif
  } FrameInfo;
  
  /* Max number of frames stored in the TLS data */
  #define MAX_FRAMES 50
  
  /*
   * Per-thread data kept by this module. This is stored in the GC and passed to us as
   * parameters, instead of being stored in a TLS variable, since during a collection,
   * only the collection thread is active.
   */
  typedef struct {
  	MonoLMF *lmf;
  	MonoContext ctx;
  	gboolean has_context;
  	MonoJitTlsData *jit_tls;
  	/* For debugging */
  	mgreg_t tid;
  	gpointer ref_to_track;
  	/* Number of frames collected during the !precise pass */
  	int nframes;
  	FrameInfo frames [MAX_FRAMES];
  } TlsData;
  
  /* These are constant so don't store them in the GC Maps */
  /* Number of registers stored in gc maps */
  #define NREGS MONO_MAX_IREGS
  
  /* 
   * The GC Map itself.
   * Contains information needed to mark a stack frame.
   * This is a transient structure, created from a compressed representation on-demand.
   */
  typedef struct {
  	/*
  	 * The offsets of the GC tracked area inside the stack frame relative to the frame pointer.
  	 * This includes memory which is NOREF thus doesn't need GC maps.
  	 */
  	int start_offset;
  	int end_offset;
  	/*
  	 * The offset relative to frame_offset where the the memory described by the GC maps
  	 * begins.
  	 */
  	int map_offset;
  	/* The number of stack slots in the map */
  	int nslots;
  	/* The frame pointer register */
  	guint8 frame_reg;
  	/* The size of each callsite table entry */
  	guint8 callsite_entry_size;
  	guint has_pin_slots : 1;
  	guint has_ref_slots : 1;
  	guint has_ref_regs : 1;
  	guint has_pin_regs : 1;
  
  	/* The offsets below are into an external bitmaps array */
  
  	/* 
  	 * A bitmap whose width is equal to bitmap_width, and whose height is equal to ncallsites.
  	 * The bitmap contains a 1 if the corresponding stack slot has type SLOT_REF at the
  	 * given callsite.
  	 */
  	guint32 stack_ref_bitmap_offset;
  	/*
  	 * Same for SLOT_PIN. It is possible that the same bit is set in both bitmaps at
       * different callsites, if the slot starts out as PIN, and later changes to REF.
  	 */
  	guint32 stack_pin_bitmap_offset;
  
  	/*
  	 * Corresponding bitmaps for registers
  	 * These have width equal to the number of bits set in reg_ref_mask/reg_pin_mask.
  	 * FIXME: Merge these with the normal bitmaps, i.e. reserve the first x slots for them ?
  	 */
  	guint32 reg_pin_bitmap_offset;
  	guint32 reg_ref_bitmap_offset;
  
  	guint32 used_int_regs, reg_ref_mask, reg_pin_mask;
  
  	/* The number of bits set in the two masks above */
  	guint8 nref_regs, npin_regs;
  
  	/*
  	 * A bit array marking slots which contain refs.
  	 * This is used only for debugging.
  	 */
  	//guint8 *ref_slots;
  
  	/* Callsite offsets */
  	/* These can take up a lot of space, so encode them compactly */
  	union {
  		guint8 *offsets8;
  		guint16 *offsets16;
  		guint32 *offsets32;
  	} callsites;
  	int ncallsites;
  } GCMap;
  
  /*
   * A compressed version of GCMap. This is what gets stored in MonoJitInfo.
   */
  typedef struct {
  	//guint8 *ref_slots;
  	//guint8 encoded_size;
  
  	/*
  	 * The arrays below are embedded after the struct.
  	 * Their address needs to be computed.
  	 */
  
  	/* The fixed fields of the GCMap encoded using LEB128 */
  	guint8 encoded [MONO_ZERO_LEN_ARRAY];
  
  	/* An array of ncallsites entries, each entry is callsite_entry_size bytes long */
  	guint8 callsites [MONO_ZERO_LEN_ARRAY];
  
  	/* The GC bitmaps */
  	guint8 bitmaps [MONO_ZERO_LEN_ARRAY];
  } GCEncodedMap;
  
  static int precise_frame_count [2], precise_frame_limit = -1;
  static gboolean precise_frame_limit_inited;
  
  /* Stats */
  typedef struct {
  	int scanned_stacks;
  	int scanned;
  	int scanned_precisely;
  	int scanned_conservatively;
  	int scanned_registers;
  	int scanned_native;
  	int scanned_other;
  	
  	int all_slots;
  	int noref_slots;
  	int ref_slots;
  	int pin_slots;
  
  	int gc_maps_size;
  	int gc_callsites_size;
  	int gc_callsites8_size;
  	int gc_callsites16_size;
  	int gc_callsites32_size;
  	int gc_bitmaps_size;
  	int gc_map_struct_size;
  	int tlsdata_size;
  } JITGCStats;
  
  static JITGCStats stats;
  
  static FILE *logfile;
  
  // FIXME: Move these to a shared place
  
  static inline void
  encode_uleb128 (guint32 value, guint8 *buf, guint8 **endbuf)
  {
  	guint8 *p = buf;
  
  	do {
  		guint8 b = value & 0x7f;
  		value >>= 7;
  		if (value != 0) /* more bytes to come */
  			b |= 0x80;
  		*p ++ = b;
  	} while (value);
  
  	*endbuf = p;
  }
  
  static G_GNUC_UNUSED void
  encode_sleb128 (gint32 value, guint8 *buf, guint8 **endbuf)
  {
  	gboolean more = 1;
  	gboolean negative = (value < 0);
  	guint32 size = 32;
  	guint8 byte;
  	guint8 *p = buf;
  
  	while (more) {
  		byte = value & 0x7f;
  		value >>= 7;
  		/* the following is unnecessary if the
  		 * implementation of >>= uses an arithmetic rather
  		 * than logical shift for a signed left operand
  		 */
  		if (negative)
  			/* sign extend */
  			value |= - (1 <<(size - 7));
  		/* sign bit of byte is second high order bit (0x40) */
  		if ((value == 0 && !(byte & 0x40)) ||
  			(value == -1 && (byte & 0x40)))
  			more = 0;
  		else
  			byte |= 0x80;
  		*p ++= byte;
  	}
  
  	*endbuf = p;
  }
  
  static inline guint32
  decode_uleb128 (guint8 *buf, guint8 **endbuf)
  {
  	guint8 *p = buf;
  	guint32 res = 0;
  	int shift = 0;
  
  	while (TRUE) {
  		guint8 b = *p;
  		p ++;
  
  		res = res | (((int)(b & 0x7f)) << shift);
  		if (!(b & 0x80))
  			break;
  		shift += 7;
  	}
  
  	*endbuf = p;
  
  	return res;
  }
  
  static inline gint32
  decode_sleb128 (guint8 *buf, guint8 **endbuf)
  {
  	guint8 *p = buf;
  	gint32 res = 0;
  	int shift = 0;
  
  	while (TRUE) {
  		guint8 b = *p;
  		p ++;
  
  		res = res | (((int)(b & 0x7f)) << shift);
  		shift += 7;
  		if (!(b & 0x80)) {
  			if (shift < 32 && (b & 0x40))
  				res |= - (1 << shift);
  			break;
  		}
  	}
  
  	*endbuf = p;
  
  	return res;
  }
  
  static int
  encode_frame_reg (int frame_reg)
  {
  #ifdef TARGET_AMD64
  	if (frame_reg == AMD64_RSP)
  		return 0;
  	else if (frame_reg == AMD64_RBP)
  		return 1;
  #elif defined(TARGET_X86)
  	if (frame_reg == X86_EBP)
  		return 0;
  	else if (frame_reg == X86_ESP)
  		return 1;
  #else
  	NOT_IMPLEMENTED;
  #endif
  	g_assert_not_reached ();
  	return -1;
  }
  
  static int
  decode_frame_reg (int encoded)
  {
  #ifdef TARGET_AMD64
  	if (encoded == 0)
  		return AMD64_RSP;
  	else if (encoded == 1)
  		return AMD64_RBP;
  #elif defined(TARGET_X86)
  	if (encoded == 0)
  		return X86_EBP;
  	else if (encoded == 1)
  		return X86_ESP;
  #else
  	NOT_IMPLEMENTED;
  #endif
  	g_assert_not_reached ();
  	return -1;
  }
  
  #ifdef TARGET_AMD64
  #ifdef HOST_WIN32
  static int callee_saved_regs [] = { AMD64_RBP, AMD64_RBX, AMD64_R12, AMD64_R13, AMD64_R14, AMD64_R15, AMD64_RDI, AMD64_RSI };
  #else
  static int callee_saved_regs [] = { AMD64_RBP, AMD64_RBX, AMD64_R12, AMD64_R13, AMD64_R14, AMD64_R15 };
  #endif
  #elif defined(TARGET_X86)
  static int callee_saved_regs [] = { X86_EBX, X86_ESI, X86_EDI };
  #endif
  
  static guint32
  encode_regmask (guint32 regmask)
  {
  	int i;
  	guint32 res;
  
  	res = 0;
  	for (i = 0; i < sizeof (callee_saved_regs) / sizeof (int); ++i) {
  		if (regmask & (1 << callee_saved_regs [i])) {
  			res |= (1 << i);
  			regmask -= (1 << callee_saved_regs [i]);
  		}
  	}
  	g_assert (regmask == 0);
  	return res;
  }
  
  static guint32
  decode_regmask (guint32 regmask)
  {
  	int i;
  	guint32 res;
  
  	res = 0;
  	for (i = 0; i < sizeof (callee_saved_regs) / sizeof (int); ++i)
  		if (regmask & (1 << i))
  			res |= (1 << callee_saved_regs [i]);
  	return res;
  }
  
  /*
   * encode_gc_map:
   *
   *   Encode the fixed fields of MAP into a buffer pointed to by BUF.
   */
  static void
  encode_gc_map (GCMap *map, guint8 *buf, guint8 **endbuf)
  {
  	guint32 flags, freg;
  
  	encode_sleb128 (map->start_offset / sizeof (mgreg_t), buf, &buf);
  	encode_sleb128 (map->end_offset / sizeof (mgreg_t), buf, &buf);
  	encode_sleb128 (map->map_offset / sizeof (mgreg_t), buf, &buf);
  	encode_uleb128 (map->nslots, buf, &buf);
  	g_assert (map->callsite_entry_size <= 4);
  	freg = encode_frame_reg (map->frame_reg);
  	g_assert (freg < 2);
  	flags = (map->has_ref_slots ? 1 : 0) | (map->has_pin_slots ? 2 : 0) | (map->has_ref_regs ? 4 : 0) | (map->has_pin_regs ? 8 : 0) | ((map->callsite_entry_size - 1) << 4) | (freg << 6);
  	encode_uleb128 (flags, buf, &buf);
  	encode_uleb128 (encode_regmask (map->used_int_regs), buf, &buf);
  	if (map->has_ref_regs)
  		encode_uleb128 (encode_regmask (map->reg_ref_mask), buf, &buf);
  	if (map->has_pin_regs)
  		encode_uleb128 (encode_regmask (map->reg_pin_mask), buf, &buf);
  	encode_uleb128 (map->ncallsites, buf, &buf);
  
  	*endbuf = buf;
  }	
  
  /*
   * decode_gc_map:
   *
   *   Decode the encoded GC map representation in BUF and store the result into MAP.
   */
  static void
  decode_gc_map (guint8 *buf, GCMap *map, guint8 **endbuf)
  {
  	guint32 flags;
  	int stack_bitmap_size, reg_ref_bitmap_size, reg_pin_bitmap_size, offset, freg;
  	int i, n;
  
  	map->start_offset = decode_sleb128 (buf, &buf) * sizeof (mgreg_t);
  	map->end_offset = decode_sleb128 (buf, &buf) * sizeof (mgreg_t);
  	map->map_offset = decode_sleb128 (buf, &buf) * sizeof (mgreg_t);
  	map->nslots = decode_uleb128 (buf, &buf);
  	flags = decode_uleb128 (buf, &buf);
  	map->has_ref_slots = (flags & 1) ? 1 : 0;
  	map->has_pin_slots = (flags & 2) ? 1 : 0;
  	map->has_ref_regs = (flags & 4) ? 1 : 0;
  	map->has_pin_regs = (flags & 8) ? 1 : 0;
  	map->callsite_entry_size = ((flags >> 4) & 0x3) + 1;
  	freg = flags >> 6;
  	map->frame_reg = decode_frame_reg (freg);
  	map->used_int_regs = decode_regmask (decode_uleb128 (buf, &buf));
  	if (map->has_ref_regs) {
  		map->reg_ref_mask = decode_regmask (decode_uleb128 (buf, &buf));
  		n = 0;
  		for (i = 0; i < NREGS; ++i)
  			if (map->reg_ref_mask & (1 << i))
  				n ++;
  		map->nref_regs = n;
  	}
  	if (map->has_pin_regs) {
  		map->reg_pin_mask = decode_regmask (decode_uleb128 (buf, &buf));
  		n = 0;
  		for (i = 0; i < NREGS; ++i)
  			if (map->reg_pin_mask & (1 << i))
  				n ++;
  		map->npin_regs = n;
  	}
  	map->ncallsites = decode_uleb128 (buf, &buf);
  
  	stack_bitmap_size = (ALIGN_TO (map->nslots, 8) / 8) * map->ncallsites;
  	reg_ref_bitmap_size = (ALIGN_TO (map->nref_regs, 8) / 8) * map->ncallsites;
  	reg_pin_bitmap_size = (ALIGN_TO (map->npin_regs, 8) / 8) * map->ncallsites;
  	offset = 0;
  	map->stack_ref_bitmap_offset = offset;
  	if (map->has_ref_slots)
  		offset += stack_bitmap_size;
  	map->stack_pin_bitmap_offset = offset;
  	if (map->has_pin_slots)
  		offset += stack_bitmap_size;
  	map->reg_ref_bitmap_offset = offset;
  	if (map->has_ref_regs)
  		offset += reg_ref_bitmap_size;
  	map->reg_pin_bitmap_offset = offset;
  	if (map->has_pin_regs)
  		offset += reg_pin_bitmap_size;
  
  	*endbuf = buf;
  }
  
  static gpointer
  thread_attach_func (void)
  {
  	TlsData *tls;
  
  	tls = g_new0 (TlsData, 1);
  	tls->tid = GetCurrentThreadId ();
  	stats.tlsdata_size += sizeof (TlsData);
  
  	return tls;
  }
  
  static void
  thread_detach_func (gpointer user_data)
  {
  	TlsData *tls = user_data;
  
  	g_free (tls);
  }
  
  static void
  thread_suspend_func (gpointer user_data, void *sigctx)
  {
  	TlsData *tls = user_data;
  
  	if (!tls)
  		/* Happens during startup */
  		return;
  
  	tls->lmf = mono_get_lmf ();
  	if (sigctx) {
  		mono_arch_sigctx_to_monoctx (sigctx, &tls->ctx);
  		tls->has_context = TRUE;
  	} else {
  		tls->has_context = FALSE;
  	}
  	tls->jit_tls = TlsGetValue (mono_jit_tls_id);
  }
  
  #define DEAD_REF ((gpointer)(gssize)0x2a2a2a2a2a2a2a2aULL)
  
  static inline void
  set_bit (guint8 *bitmap, int width, int y, int x)
  {
  	bitmap [(width * y) + (x / 8)] |= (1 << (x % 8));
  }
  
  static inline void
  clear_bit (guint8 *bitmap, int width, int y, int x)
  {
  	bitmap [(width * y) + (x / 8)] &= ~(1 << (x % 8));
  }
  
  static inline int
  get_bit (guint8 *bitmap, int width, int y, int x)
  {
  	return bitmap [(width * y) + (x / 8)] & (1 << (x % 8));
  }
  
  static const char*
  slot_type_to_string (GCSlotType type)
  {
  	switch (type) {
  	case SLOT_REF:
  		return "ref";
  	case SLOT_NOREF:
  		return "noref";
  	case SLOT_PIN:
  		return "pin";
  	default:
  		g_assert_not_reached ();
  		return NULL;
  	}
  }
  
  static inline mgreg_t
  get_frame_pointer (MonoContext *ctx, int frame_reg)
  {
  #if defined(TARGET_AMD64)
  		if (frame_reg == AMD64_RSP)
  			return ctx->rsp;
  		else if (frame_reg == AMD64_RBP)
  			return ctx->rbp;
  #elif defined(TARGET_X86)
  		if (frame_reg == X86_ESP)
  			return ctx->esp;
  		else if (frame_reg == X86_EBP)
  			return ctx->ebp;
  #endif
  		g_assert_not_reached ();
  		return 0;
  }
  
  /*
   * conservatively_pass:
   *
   *   Mark a thread stack conservatively and collect information needed by the precise pass.
   */
  static void
  conservative_pass (TlsData *tls, guint8 *stack_start, guint8 *stack_end)
  {
  	MonoJitInfo *ji;
  	MonoContext ctx, new_ctx;
  	MonoLMF *lmf;
  	guint8 *stack_limit;
  	gboolean last = TRUE;
  	GCMap *map;
  	GCMap map_tmp;
  	GCEncodedMap *emap;
  	guint8* fp, *p, *real_frame_start, *frame_start, *frame_end;
  	int i, pc_offset, cindex, bitmap_width;
  	int scanned = 0, scanned_precisely, scanned_conservatively, scanned_registers;
  	gboolean res;
  	StackFrameInfo frame;
  	mgreg_t *reg_locations [MONO_MAX_IREGS];
  	mgreg_t *new_reg_locations [MONO_MAX_IREGS];
  	guint8 *bitmaps;
  	FrameInfo *fi;
  	guint32 precise_regmask;
  
  	if (tls) {
  		tls->nframes = 0;
  		tls->ref_to_track = NULL;
  	}
  
  	/* tls == NULL can happen during startup */
  	if (mono_thread_internal_current () == NULL || !tls) {
  		mono_gc_conservatively_scan_area (stack_start, stack_end);
  		stats.scanned_stacks += stack_end - stack_start;
  		return;
  	}
  
  	lmf = tls->lmf;
  	frame.domain = NULL;
  
  	/* Number of bytes scanned based on GC map data */
  	scanned = 0;
  	/* Number of bytes scanned precisely based on GC map data */
  	scanned_precisely = 0;
  	/* Number of bytes scanned conservatively based on GC map data */
  	scanned_conservatively = 0;
  	/* Number of bytes scanned conservatively in register save areas */
  	scanned_registers = 0;
  
  	/* This is one past the last address which we have scanned */
  	stack_limit = stack_start;
  
  	if (!tls->has_context)
  		memset (&new_ctx, 0, sizeof (ctx));
  	else
  		memcpy (&new_ctx, &tls->ctx, sizeof (MonoContext));
  
  	memset (reg_locations, 0, sizeof (reg_locations));
  	memset (new_reg_locations, 0, sizeof (new_reg_locations));
  
  	while (TRUE) {
  		memcpy (&ctx, &new_ctx, sizeof (ctx));
  
  		for (i = 0; i < MONO_MAX_IREGS; ++i) {
  			if (new_reg_locations [i]) {
  				/*
  				 * If the current frame saves the register, it means it might modify its
  				 * value, thus the old location might not contain the same value, so
  				 * we have to mark it conservatively.
  				 */
  				if (reg_locations [i]) {
  					DEBUG (fprintf (logfile, "\tscan saved reg %s location %p.\n", mono_arch_regname (i), reg_locations [i]));
  					mono_gc_conservatively_scan_area (reg_locations [i], reg_locations [i] + sizeof (mgreg_t));
  					scanned_registers += sizeof (mgreg_t);
  				}
  
  				reg_locations [i] = new_reg_locations [i];
  
  				DEBUG (fprintf (logfile, "\treg %s is now at location %p.\n", mono_arch_regname (i), reg_locations [i]));
  			}
  		}
  
  		g_assert ((mgreg_t)stack_limit % sizeof (mgreg_t) == 0);
  
  		res = mono_find_jit_info_ext (frame.domain ? frame.domain : mono_domain_get (), tls->jit_tls, NULL, &ctx, &new_ctx, NULL, &lmf, new_reg_locations, &frame);
  		if (!res)
  			break;
  
  		ji = frame.ji;
  
  		if (frame.type == FRAME_TYPE_MANAGED_TO_NATIVE) {
  			/*
  			 * These frames are problematic for several reasons:
  			 * - they are unwound through an LMF, and we have no precise register tracking for those.
  			 * - the LMF might not contain a precise ip, so we can't compute the call site.
  			 * - the LMF only unwinds to the wrapper frame, so we get these methods twice.
  			 */
  			DEBUG (fprintf (logfile, "Mark(0): <Managed-to-native transition>\n"));
  			for (i = 0; i < MONO_MAX_IREGS; ++i) {
  				if (reg_locations [i]) {
  					DEBUG (fprintf (logfile, "\tscan saved reg %s location %p.\n", mono_arch_regname (i), reg_locations [i]));
  					mono_gc_conservatively_scan_area (reg_locations [i], reg_locations [i] + sizeof (mgreg_t));
  					scanned_registers += sizeof (mgreg_t);
  				}
  				reg_locations [i] = NULL;
  				new_reg_locations [i] = NULL;
  			}
  			ctx = new_ctx;
  			continue;
  		}
  
  		/* The last frame can be in any state so mark conservatively */
  		if (last) {
  			if (ji) {
  				DEBUG (char *fname = mono_method_full_name (ji->method, TRUE); fprintf (logfile, "Mark(0): %s+0x%x (%p)\n", fname, pc_offset, (gpointer)MONO_CONTEXT_GET_IP (&ctx)); g_free (fname));
  			}
  			DEBUG (fprintf (logfile, "\t <Last frame>\n"));
  			last = FALSE;
  			continue;
  		}
  
  		pc_offset = (guint8*)MONO_CONTEXT_GET_IP (&ctx) - (guint8*)ji->code_start;
  
  		/* These frames are very problematic */
  		if (ji->method->wrapper_type == MONO_WRAPPER_MANAGED_TO_NATIVE) {
  			DEBUG (char *fname = mono_method_full_name (ji->method, TRUE); fprintf (logfile, "Mark(0): %s+0x%x (%p)\n", fname, pc_offset, (gpointer)MONO_CONTEXT_GET_IP (&ctx)); g_free (fname));
  			DEBUG (fprintf (logfile, "\tSkip.\n"));
  			continue;
  		}
  
  		/* All the other frames are at a call site */
  
  		if (tls->nframes == MAX_FRAMES) {
  			/* 
  			 * Can't save information since the array is full. So scan the rest of the
  			 * stack conservatively.
  			 */
  			DEBUG (fprintf (logfile, "Mark (0): Frame stack full.\n"));
  			break;
  		}
  
  		/* Scan the frame of this method */
  
  		/*
  		 * A frame contains the following:
  		 * - saved registers
  		 * - saved args
  		 * - locals
  		 * - spill area
  		 * - localloc-ed memory
  		 */
  		g_assert (pc_offset >= 0);
  
  		emap = ji->gc_info;
  
  		if (!emap) {
  			DEBUG (char *fname = mono_method_full_name (ji->method, TRUE); fprintf (logfile, "Mark(0): %s+0x%x (%p)\n", fname, pc_offset, (gpointer)MONO_CONTEXT_GET_IP (&ctx)); g_free (fname));
  			DEBUG (fprintf (logfile, "\tNo GC Map.\n"));
  			continue;
  		}
  
  		/* The embedded callsite table requires this */
  		g_assert (((mgreg_t)emap % 4) == 0);
  
  		/*
  		 * Debugging aid to control the number of frames scanned precisely
  		 */
  		if (!precise_frame_limit_inited) {
  			if (getenv ("MONO_PRECISE_COUNT"))
  				precise_frame_limit = atoi (getenv ("MONO_PRECISE_COUNT"));
  			precise_frame_limit_inited = TRUE;
  		}
  				
  		if (precise_frame_limit != -1) {
  			if (precise_frame_count [FALSE] == precise_frame_limit)
  				printf ("LAST PRECISE FRAME: %s\n", mono_method_full_name (ji->method, TRUE));
  			if (precise_frame_count [FALSE] > precise_frame_limit)
  				continue;
  		}
  		precise_frame_count [FALSE] ++;
  
  		/* Decode the encoded GC map */
  		map = &map_tmp;
  		memset (map, 0, sizeof (GCMap));
  		decode_gc_map (&emap->encoded [0], map, &p);
  		p = (guint8*)ALIGN_TO (p, map->callsite_entry_size);
  		map->callsites.offsets8 = p;
  		p += map->callsite_entry_size * map->ncallsites;
  		bitmaps = p;
  
  		fp = (guint8*)get_frame_pointer (&ctx, map->frame_reg);
  
  		real_frame_start = fp + map->start_offset;
  		frame_start = fp + map->start_offset + map->map_offset;
  		frame_end = fp + map->end_offset;
  
  		DEBUG (char *fname = mono_method_full_name (ji->method, TRUE); fprintf (logfile, "Mark(0): %s+0x%x (%p) limit=%p fp=%p frame=%p-%p (%d)\n", fname, pc_offset, (gpointer)MONO_CONTEXT_GET_IP (&ctx), stack_limit, fp, frame_start, frame_end, (int)(frame_end - frame_start)); g_free (fname));
  
  		/* Find the callsite index */
  		if (map->callsite_entry_size == 1) {
  			for (i = 0; i < map->ncallsites; ++i)
  				/* ip points inside the call instruction */
  				if (map->callsites.offsets8 [i] == pc_offset + 1)
  					break;
  		} else if (map->callsite_entry_size == 2) {
  			// FIXME: Use a binary search
  			for (i = 0; i < map->ncallsites; ++i)
  				/* ip points inside the call instruction */
  				if (map->callsites.offsets16 [i] == pc_offset + 1)
  					break;
  		} else {
  			// FIXME: Use a binary search
  			for (i = 0; i < map->ncallsites; ++i)
  				/* ip points inside the call instruction */
  				if (map->callsites.offsets32 [i] == pc_offset + 1)
  					break;
  		}
  		if (i == map->ncallsites) {
  			printf ("Unable to find ip offset 0x%x in callsite list of %s.\n", pc_offset + 1, mono_method_full_name (ji->method, TRUE));
  			g_assert_not_reached ();
  		}
  		cindex = i;
  
  		g_assert (real_frame_start >= stack_limit);
  
  		if (real_frame_start > stack_limit) {
  			/* This scans the previously skipped frames as well */
  			DEBUG (fprintf (logfile, "\tscan area %p-%p (%d).\n", stack_limit, real_frame_start, (int)(real_frame_start - stack_limit)));
  			mono_gc_conservatively_scan_area (stack_limit, real_frame_start);
  			stats.scanned_other += real_frame_start - stack_limit;
  		}
  
  		/* Mark stack slots */
  		if (map->has_pin_slots) {
  			int bitmap_width = ALIGN_TO (map->nslots, 8) / 8;
  			guint8 *pin_bitmap = &bitmaps [map->stack_pin_bitmap_offset + (bitmap_width * cindex)];
  			guint8 *p;
  			gboolean pinned;
  
  			p = frame_start;
  			for (i = 0; i < map->nslots; ++i) {
  				pinned = pin_bitmap [i / 8] & (1 << (i % 8));
  				if (pinned) {
  					DEBUG (fprintf (logfile, "\tscan slot %s0x%x(fp)=%p.\n", (guint8*)p > (guint8*)fp ? "" : "-", ABS ((int)((gssize)p - (gssize)fp)), p));
  					mono_gc_conservatively_scan_area (p, p + sizeof (mgreg_t));
  					scanned_conservatively += sizeof (mgreg_t);
  				} else {
  					scanned_precisely += sizeof (mgreg_t);
  				}
  				p += sizeof (mgreg_t);
  			}
  		} else {
  			scanned_precisely += (map->nslots * sizeof (mgreg_t));
  		}
  
  		/* The area outside of start-end is NOREF */
  		scanned_precisely += (map->end_offset - map->start_offset) - (map->nslots * sizeof (mgreg_t));
  
  		/* Mark registers */
  		precise_regmask = map->used_int_regs | (1 << map->frame_reg);
  		if (map->has_pin_regs) {
  			int bitmap_width = ALIGN_TO (map->npin_regs, 8) / 8;
  			guint8 *pin_bitmap = &bitmaps [map->reg_pin_bitmap_offset + (bitmap_width * cindex)];
  			int bindex = 0;
  			for (i = 0; i < NREGS; ++i) {
  				if (!(map->used_int_regs & (1 << i)))
  					continue;
  				
  				if (!(map->reg_pin_mask & (1 << i)))
  					continue;
  
  				if (pin_bitmap [bindex / 8] & (1 << (bindex % 8))) {
  					DEBUG (fprintf (logfile, "\treg %s saved at 0x%p is pinning.\n", mono_arch_regname (i), reg_locations [i]));
  					precise_regmask &= ~(1 << i);
  				}
  				bindex ++;
  			}
  		}
  
  		scanned += map->end_offset - map->start_offset;
  
  		g_assert (scanned == scanned_precisely + scanned_conservatively);
  
  		stack_limit = frame_end;
  
  		/* Save information for the precise pass */
  		fi = &tls->frames [tls->nframes];
  		fi->nslots = map->nslots;
  		bitmap_width = ALIGN_TO (map->nslots, 8) / 8;
  		if (map->has_ref_slots)
  			fi->bitmap = &bitmaps [map->stack_ref_bitmap_offset + (bitmap_width * cindex)];
  		else
  			fi->bitmap = NULL;
  		fi->frame_start_offset = frame_start - stack_start;
  		fi->nreg_locations = 0;
  		DEBUG_PRECISE (fi->ji = ji);
  		DEBUG_PRECISE (fi->fp = fp);
  
  		if (map->has_ref_regs) {
  			int bitmap_width = ALIGN_TO (map->nref_regs, 8) / 8;
  			guint8 *ref_bitmap = &bitmaps [map->reg_ref_bitmap_offset + (bitmap_width * cindex)];
  			int bindex = 0;
  			for (i = 0; i < NREGS; ++i) {
  				if (!(map->reg_ref_mask & (1 << i)))
  					continue;
  
  				if (reg_locations [i] && (ref_bitmap [bindex / 8] & (1 << (bindex % 8)))) {
  					DEBUG_PRECISE (fi->regs [fi->nreg_locations] = i);
  					DEBUG (fprintf (logfile, "\treg %s saved at 0x%p is ref.\n", mono_arch_regname (i), reg_locations [i]));
  					fi->reg_locations [fi->nreg_locations] = (guint8*)reg_locations [i] - stack_start;
  					fi->nreg_locations ++;
  				}
  				bindex ++;
  			}
  		}
  
  		/*
  		 * Clear locations of precisely stacked registers.
  		 */
  		if (precise_regmask) {
  			for (i = 0; i < NREGS; ++i) {
  				if (precise_regmask & (1 << i)) {
  					/*
  					 * The method uses this register, and we have precise info for it.
  					 * This means the location will be scanned precisely.
  					 * Tell the code at the beginning of the loop that this location is
  					 * processed.
  					 */
  					if (reg_locations [i])
  						DEBUG (fprintf (logfile, "\treg %s at location %p (==%p) is precise.\n", mono_arch_regname (i), reg_locations [i], (gpointer)*reg_locations [i]));
  					reg_locations [i] = NULL;
  				}
  			}
  		}
  
  		tls->nframes ++;
  	}
  
  	/* Scan the remaining register save locations */
  	for (i = 0; i < MONO_MAX_IREGS; ++i) {
  		if (reg_locations [i]) {
  			DEBUG (fprintf (logfile, "\tscan saved reg location %p.\n", reg_locations [i]));
  			mono_gc_conservatively_scan_area (reg_locations [i], reg_locations [i] + sizeof (mgreg_t));
  			scanned_registers += sizeof (mgreg_t);
  		}
  		if (new_reg_locations [i]) {
  			DEBUG (fprintf (logfile, "\tscan saved reg location %p.\n", new_reg_locations [i]));
  			mono_gc_conservatively_scan_area (new_reg_locations [i], new_reg_locations [i] + sizeof (mgreg_t));
  			scanned_registers += sizeof (mgreg_t);
  		}
  	}
  
  	if (stack_limit < stack_end) {
  		DEBUG (fprintf (logfile, "\tscan remaining stack %p-%p (%d).\n", stack_limit, stack_end, (int)(stack_end - stack_limit)));
  		mono_gc_conservatively_scan_area (stack_limit, stack_end);
  		stats.scanned_native += stack_end - stack_limit;
  	}
  
  	DEBUG (fprintf (logfile, "Marked %d bytes, p=%d,c=%d out of %d.\n", scanned, scanned_precisely, scanned_conservatively, (int)(stack_end - stack_start)));
  
  	stats.scanned_stacks += stack_end - stack_start;
  	stats.scanned += scanned;
  	stats.scanned_precisely += scanned_precisely;
  	stats.scanned_conservatively += scanned_conservatively;
  	stats.scanned_registers += scanned_registers;
  
  	//mono_gc_conservatively_scan_area (stack_start, stack_end);
  }
  
  /*
   * precise_pass:
   *
   *   Mark a thread stack precisely based on information saved during the conservative
   * pass.
   */
  static void
  precise_pass (TlsData *tls, guint8 *stack_start, guint8 *stack_end)
  {
  	int findex, i;
  	FrameInfo *fi;
  	guint8 *frame_start;
  
  	if (!tls)
  		return;
  
  	for (findex = 0; findex < tls->nframes; findex ++) {
  		/* Load information saved by the !precise pass */
  		fi = &tls->frames [findex];
  		frame_start = stack_start + fi->frame_start_offset;
  
  		DEBUG (char *fname = mono_method_full_name (fi->ji->method, TRUE); fprintf (logfile, "Mark(1): %s\n", fname); g_free (fname));
  
  		/* 
  		 * FIXME: Add a function to mark using a bitmap, to avoid doing a 
  		 * call for each object.
  		 */
  
  		/* Mark stack slots */
  		if (fi->bitmap) {
  			guint8 *ref_bitmap = fi->bitmap;
  			gboolean live;
  
  			for (i = 0; i < fi->nslots; ++i) {
  				MonoObject **ptr = (MonoObject**)(frame_start + (i * sizeof (mgreg_t)));
  
  				live = ref_bitmap [i / 8] & (1 << (i % 8));
  
  				if (live) {
  					MonoObject *obj = *ptr;
  					if (obj) {
  						DEBUG (fprintf (logfile, "\tref %s0x%x(fp)=%p: %p ->", (guint8*)ptr >= (guint8*)fi->fp ? "" : "-", ABS ((int)((gssize)ptr - (gssize)fi->fp)), ptr, obj));
  						*ptr = mono_gc_scan_object (obj);
  						DEBUG (fprintf (logfile, " %p.\n", *ptr));
  					} else {
  						DEBUG (fprintf (logfile, "\tref %s0x%x(fp)=%p: %p.\n", (guint8*)ptr >= (guint8*)fi->fp ? "" : "-", ABS ((int)((gssize)ptr - (gssize)fi->fp)), ptr, obj));
  					}
  				} else {
  #if 0
  					/*
  					 * This is disabled because the pointer takes up a lot of space.
  					 * Stack slots might be shared between ref and non-ref variables ?
  					 */
  					if (map->ref_slots [i / 8] & (1 << (i % 8))) {
  						DEBUG (fprintf (logfile, "\tref %s0x%x(fp)=%p: dead (%p)\n", (guint8*)ptr >= (guint8*)fi->fp ? "" : "-", ABS ((int)((gssize)ptr - (gssize)fi->fp)), ptr, *ptr));
  						/*
  						 * Fail fast if the live range is incorrect, and
  						 * the JITted code tries to access this object
  						 */
  						*ptr = DEAD_REF;
  					}
  #endif
  				}
  			}
  		}
  
  		/* Mark registers */
  
  		/*
  		 * Registers are different from stack slots, they have no address where they
  		 * are stored. Instead, some frame below this frame in the stack saves them
  		 * in its prolog to the stack. We can mark this location precisely.
  		 */
  		for (i = 0; i < fi->nreg_locations; ++i) {
  			/*
  			 * reg_locations [i] contains the address of the stack slot where
  			 * a reg was last saved, so mark that slot.
  			 */
  			MonoObject **ptr = (MonoObject**)((guint8*)stack_start + fi->reg_locations [i]);
  			MonoObject *obj = *ptr;
  
  			if (obj) {
  				DEBUG (fprintf (logfile, "\treg %s saved at %p: %p ->", mono_arch_regname (fi->regs [i]), ptr, obj));
  				*ptr = mono_gc_scan_object (obj);
  				DEBUG (fprintf (logfile, " %p.\n", *ptr));
  			} else {
  				DEBUG (fprintf (logfile, "\treg %s saved at %p: %p\n", mono_arch_regname (fi->regs [i]), ptr, obj));
  			}
  		}	
  	}
  
  	/*
  	 * Debugging aid to check for missed refs.
  	 */
  	if (tls->ref_to_track) {
  		mgreg_t *p;
  
  		for (p = (mgreg_t*)stack_start; p < (mgreg_t*)stack_end; ++p)
  			if (*p == (mgreg_t)tls->ref_to_track)
  				printf ("REF AT %p.\n", p);
  	}
  }
  
  /*
   * thread_mark_func:
   *
   *   This is called by the GC twice to mark a thread stack. PRECISE is FALSE at the first
   * call, and TRUE at the second. USER_DATA points to a TlsData
   * structure filled up by thread_suspend_func. 
   */
  static void
  thread_mark_func (gpointer user_data, guint8 *stack_start, guint8 *stack_end, gboolean precise)
  {
  	TlsData *tls = user_data;
  
  	DEBUG (fprintf (logfile, "****************************************\n"));
  	DEBUG (fprintf (logfile, "*** %s stack marking for thread %p (%p-%p) ***\n", precise ? "Precise" : "Conservative", tls ? GUINT_TO_POINTER (tls->tid) : NULL, stack_start, stack_end));
  	DEBUG (fprintf (logfile, "****************************************\n"));
  
  	if (!precise)
  		conservative_pass (tls, stack_start, stack_end);
  	else
  		precise_pass (tls, stack_start, stack_end);
  }
  
  static void
  mini_gc_init_gc_map (MonoCompile *cfg)
  {
  	if (COMPILE_LLVM (cfg))
  		return;
  
  	if (!cfg->compile_aot && conservative_stack_mark)
  		return;
  
  #if 1
  	/* Debugging support */
  	{
  		static int precise_count;
  
  		precise_count ++;
  		if (getenv ("MONO_GCMAP_COUNT")) {
  			if (precise_count == atoi (getenv ("MONO_GCMAP_COUNT")))
  				printf ("LAST: %s\n", mono_method_full_name (cfg->method, TRUE));
  			if (precise_count > atoi (getenv ("MONO_GCMAP_COUNT")))
  				return;
  		}
  	}
  #endif
  
  	cfg->compute_gc_maps = TRUE;
  
  	cfg->gc_info = mono_mempool_alloc0 (cfg->mempool, sizeof (MonoCompileGC));
  }
  
  /*
   * mini_gc_set_slot_type_from_fp:
   *
   *   Set the GC slot type of the stack slot identified by SLOT_OFFSET, which should be
   * relative to the frame pointer. By default, all stack slots are type PIN, so there is no
   * need to call this function for those slots.
   */
  void
  mini_gc_set_slot_type_from_fp (MonoCompile *cfg, int slot_offset, GCSlotType type)
  {
  	MonoCompileGC *gcfg = (MonoCompileGC*)cfg->gc_info;
  
  	if (!cfg->compute_gc_maps)
  		return;
  
  	g_assert (slot_offset % sizeof (mgreg_t) == 0);
  
  	gcfg->stack_slots_from_fp = g_slist_prepend_mempool (cfg->mempool, gcfg->stack_slots_from_fp, GINT_TO_POINTER (((slot_offset) << 16) | type));
  }
  
  /*
   * mini_gc_set_slot_type_from_cfa:
   *
   *   Set the GC slot type of the stack slot identified by SLOT_OFFSET, which should be
   * relative to the DWARF CFA value. This should be called from mono_arch_emit_prolog ().
   * If type is STACK_REF, the slot is assumed to be live from the end of the prolog until
   * the end of the method. By default, all stack slots are type PIN, so there is no need to
   * call this function for those slots.
   */
  void
  mini_gc_set_slot_type_from_cfa (MonoCompile *cfg, int slot_offset, GCSlotType type)
  {
  	MonoCompileGC *gcfg = (MonoCompileGC*)cfg->gc_info;
  	int slot = - (slot_offset / sizeof (mgreg_t));
  
  	if (!cfg->compute_gc_maps)
  		return;
  
  	g_assert (slot_offset <= 0);
  	g_assert (slot_offset % sizeof (mgreg_t) == 0);
  
  	gcfg->stack_slots_from_cfa = g_slist_prepend_mempool (cfg->mempool, gcfg->stack_slots_from_cfa, GUINT_TO_POINTER (((slot) << 16) | type));
  }
  
  static inline int
  fp_offset_to_slot (MonoCompile *cfg, int offset)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  
  	return (offset - gcfg->min_offset) / sizeof (mgreg_t);
  }
  
  static inline int
  slot_to_fp_offset (MonoCompile *cfg, int slot)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  
  	return (slot * sizeof (mgreg_t)) + gcfg->min_offset;
  }
  
  static inline void
  set_slot (MonoCompileGC *gcfg, int slot, int callsite_index, GCSlotType type)
  {
  	g_assert (slot >= 0 && slot < gcfg->nslots);
  
  	if (type == SLOT_PIN) {
  		clear_bit (gcfg->stack_ref_bitmap, gcfg->stack_bitmap_width, callsite_index, slot);
  		set_bit (gcfg->stack_pin_bitmap, gcfg->stack_bitmap_width, callsite_index, slot);
  	} else if (type == SLOT_REF) {
  		set_bit (gcfg->stack_ref_bitmap, gcfg->stack_bitmap_width, callsite_index, slot);
  		clear_bit (gcfg->stack_pin_bitmap, gcfg->stack_bitmap_width, callsite_index, slot);
  	} else if (type == SLOT_NOREF) {
  		clear_bit (gcfg->stack_ref_bitmap, gcfg->stack_bitmap_width, callsite_index, slot);
  		clear_bit (gcfg->stack_pin_bitmap, gcfg->stack_bitmap_width, callsite_index, slot);
  	}
  }
  
  static inline void
  set_slot_everywhere (MonoCompileGC *gcfg, int slot, GCSlotType type)
  {
  	int cindex;
  
  	for (cindex = 0; cindex < gcfg->ncallsites; ++cindex)
  		set_slot (gcfg, slot, cindex, type);
  }
  
  static inline void
  set_slot_in_range (MonoCompileGC *gcfg, int slot, int from, int to, GCSlotType type)
  {
  	int cindex;
  
  	for (cindex = 0; cindex < gcfg->ncallsites; ++cindex) {
  		int callsite_offset = gcfg->callsites [cindex]->pc_offset;
  		if (callsite_offset >= from && callsite_offset < to)
  			set_slot (gcfg, slot, cindex, type);
  	}
  }
  
  static inline void
  set_reg_slot (MonoCompileGC *gcfg, int slot, int callsite_index, GCSlotType type)
  {
  	g_assert (slot >= 0 && slot < gcfg->nregs);
  
  	if (type == SLOT_PIN) {
  		clear_bit (gcfg->reg_ref_bitmap, gcfg->reg_bitmap_width, callsite_index, slot);
  		set_bit (gcfg->reg_pin_bitmap, gcfg->reg_bitmap_width, callsite_index, slot);
  	} else if (type == SLOT_REF) {
  		set_bit (gcfg->reg_ref_bitmap, gcfg->reg_bitmap_width, callsite_index, slot);
  		clear_bit (gcfg->reg_pin_bitmap, gcfg->reg_bitmap_width, callsite_index, slot);
  	} else if (type == SLOT_NOREF) {
  		clear_bit (gcfg->reg_ref_bitmap, gcfg->reg_bitmap_width, callsite_index, slot);
  		clear_bit (gcfg->reg_pin_bitmap, gcfg->reg_bitmap_width, callsite_index, slot);
  	}
  }
  
  static inline void
  set_reg_slot_everywhere (MonoCompileGC *gcfg, int slot, GCSlotType type)
  {
  	int cindex;
  
  	for (cindex = 0; cindex < gcfg->ncallsites; ++cindex)
  		set_reg_slot (gcfg, slot, cindex, type);
  }
  
  static inline void
  set_reg_slot_in_range (MonoCompileGC *gcfg, int slot, int from, int to, GCSlotType type)
  {
  	int cindex;
  
  	for (cindex = 0; cindex < gcfg->ncallsites; ++cindex) {
  		int callsite_offset = gcfg->callsites [cindex]->pc_offset;
  		if (callsite_offset >= from && callsite_offset < to)
  			set_reg_slot (gcfg, slot, cindex, type);
  	}
  }
  
  static void
  process_spill_slots (MonoCompile *cfg)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  	MonoBasicBlock *bb;
  	GSList *l;
  	int i;
  
  	/* Mark all ref/pin spill slots as NOREF by default outside of their live range */
  	for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  		for (l = bb->spill_slot_defs; l; l = l->next) {
  			MonoInst *def = l->data;
  			int spill_slot = def->inst_c0;
  			int bank = def->inst_c1;
  			int offset = cfg->spill_info [bank][spill_slot].offset;
  			int slot = fp_offset_to_slot (cfg, offset);
  
  			if (bank == MONO_REG_INT_MP || bank == MONO_REG_INT_REF)
  				set_slot_everywhere (gcfg, slot, SLOT_NOREF);
  		}
  	}
  
  	for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  		for (l = bb->spill_slot_defs; l; l = l->next) {
  			MonoInst *def = l->data;
  			int spill_slot = def->inst_c0;
  			int bank = def->inst_c1;
  			int offset = cfg->spill_info [bank][spill_slot].offset;
  			int slot = fp_offset_to_slot (cfg, offset);
  			GCSlotType type;
  
  			if (bank == MONO_REG_INT_MP)
  				type = SLOT_PIN;
  			else
  				type = SLOT_REF;
  
  			/*
  			 * Extend the live interval for the GC tracked spill slots
  			 * defined in this bblock.
  			 * FIXME: This is not needed.
  			 */
  			set_slot_in_range (gcfg, slot, def->backend.pc_offset, bb->native_offset + bb->native_length, type);
  
  			if (cfg->verbose_level > 1)
  				printf ("\t%s spill slot at %s0x%x(fp) (slot = %d)\n", slot_type_to_string (type), offset >= 0 ? "" : "-", ABS (offset), slot);
  		}
  	}
  
  	/* Set fp spill slots to NOREF */
  	for (i = 0; i < cfg->spill_info_len [MONO_REG_DOUBLE]; ++i) {
  		int offset = cfg->spill_info [MONO_REG_DOUBLE][i].offset;
  		int slot;
  
  		if (offset == -1)
  			continue;
  
  		slot = fp_offset_to_slot (cfg, offset);
  
  		set_slot_everywhere (gcfg, slot, SLOT_NOREF);
  		/* FIXME: 32 bit */
  		if (cfg->verbose_level > 1)
  			printf ("\tfp spill slot at %s0x%x(fp) (slot = %d)\n", offset >= 0 ? "" : "-", ABS (offset), slot);
  	}
  
  	/* Set int spill slots to NOREF */
  	for (i = 0; i < cfg->spill_info_len [MONO_REG_INT]; ++i) {
  		int offset = cfg->spill_info [MONO_REG_INT][i].offset;
  		int slot;
  
  		if (offset == -1)
  			continue;
  
  		slot = fp_offset_to_slot (cfg, offset);
  
  		set_slot_everywhere (gcfg, slot, SLOT_NOREF);
  		if (cfg->verbose_level > 1)
  			printf ("\tint spill slot at %s0x%x(fp) (slot = %d)\n", offset >= 0 ? "" : "-", ABS (offset), slot);
  	}
  }
  
  /*
   * process_other_slots:
   *
   *   Process stack slots registered using mini_gc_set_slot_type_... ().
   */
  static void
  process_other_slots (MonoCompile *cfg)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  	GSList *l;
  
  	/* Relative to the CFA */
  	for (l = gcfg->stack_slots_from_cfa; l; l = l->next) {
  		guint data = GPOINTER_TO_UINT (l->data);
  		int cfa_slot = data >> 16;
  		GCSlotType type = data & 0xff;
  		int slot;
  		
  		/*
  		 * Map the cfa relative slot to an fp relative slot.
  		 * slot_addr == cfa - <cfa_slot>*4/8
  		 * fp + cfa_offset == cfa
  		 * -> slot_addr == fp + (cfa_offset - <cfa_slot>*4/8)
  		 */
  		slot = (cfg->cfa_offset / sizeof (mgreg_t)) - cfa_slot - (gcfg->min_offset / sizeof (mgreg_t));
  
  		set_slot_everywhere (gcfg, slot, type);
  
  		if (cfg->verbose_level > 1) {
  			int fp_offset = slot_to_fp_offset (cfg, slot);
  			if (type == SLOT_NOREF)
  				printf ("\tnoref slot at %s0x%x(fp) (slot = %d) (cfa - 0x%x)\n", fp_offset >= 0 ? "" : "-", ABS (fp_offset), slot, (int)(cfa_slot * sizeof (mgreg_t)));
  		}
  	}
  
  	/* Relative to the FP */
  	for (l = gcfg->stack_slots_from_fp; l; l = l->next) {
  		gint data = GPOINTER_TO_INT (l->data);
  		int offset = data >> 16;
  		GCSlotType type = data & 0xff;
  		int slot;
  		
  		slot = fp_offset_to_slot (cfg, offset);
  
  		set_slot_everywhere (gcfg, slot, type);
  
  		/* Liveness for these slots is handled by process_spill_slots () */
  
  		if (cfg->verbose_level > 1) {
  			if (type == SLOT_REF)
  				printf ("\tref slot at fp+0x%x (slot = %d)\n", offset, slot);
  		}
  	}
  }
  
  static void
  process_variables (MonoCompile *cfg)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  	MonoMethodSignature *sig = mono_method_signature (cfg->method);
  	int i, locals_min_slot, locals_max_slot, cindex;
  	MonoBasicBlock *bb;
  	MonoInst *tmp;
  	int *pc_offsets;
  	int locals_min_offset = gcfg->locals_min_offset;
  	int locals_max_offset = gcfg->locals_max_offset;
  
  	/* Slots for locals are NOREF by default */
  	locals_min_slot = (locals_min_offset - gcfg->min_offset) / sizeof (mgreg_t);
  	locals_max_slot = (locals_max_offset - gcfg->min_offset) / sizeof (mgreg_t);
  	for (i = locals_min_slot; i < locals_max_slot; ++i) {
  		set_slot_everywhere (gcfg, i, SLOT_NOREF);
  	}
  
  	/*
  	 * Compute the offset where variables are initialized in the first bblock, if any.
  	 */
  	pc_offsets = g_new0 (int, cfg->next_vreg);
  
  	bb = cfg->bb_entry->next_bb;
  	MONO_BB_FOR_EACH_INS (bb, tmp) {
  		if (tmp->opcode == OP_GC_LIVENESS_DEF) {
  			int vreg = tmp->inst_c1;
  			if (pc_offsets [vreg] == 0) {
  				g_assert (tmp->backend.pc_offset > 0);
  				pc_offsets [vreg] = tmp->backend.pc_offset;
  			}
  		}
  	}
  
  	/*
  	 * Stack slots holding arguments are initialized in the prolog.
  	 * This means we can treat them alive for the whole method.
  	 */
  	for (i = 0; i < cfg->num_varinfo; i++) {
  		MonoInst *ins = cfg->varinfo [i];
  		MonoType *t = ins->inst_vtype;
  		MonoMethodVar *vmv;
  		guint32 pos;
  		gboolean byref, is_this = FALSE;
  		gboolean is_arg = i < cfg->locals_start;
  
  		if (ins == cfg->ret)
  			continue;
  
  		vmv = MONO_VARINFO (cfg, i);
  
  		/* For some reason, 'this' is byref */
  		if (sig->hasthis && ins == cfg->args [0] && !cfg->method->klass->valuetype) {
  			t = &cfg->method->klass->byval_arg;
  			is_this = TRUE;
  		}
  
  		byref = t->byref;
  
  		if (ins->opcode == OP_REGVAR) {
  			int hreg;
  			GCSlotType slot_type;
  
  			t = mini_type_get_underlying_type (NULL, t);
  
  			hreg = ins->dreg;
  			g_assert (hreg < MONO_MAX_IREGS);
  
  			if (byref)
  				slot_type = SLOT_PIN;
  			else
  				slot_type = MONO_TYPE_IS_REFERENCE (t) ? SLOT_REF : SLOT_NOREF;
  
  			if (slot_type == SLOT_PIN) {
  				/* These have no live interval, be conservative */
  				set_reg_slot_everywhere (gcfg, hreg, slot_type);
  			} else {
  				/*
  				 * Unlike variables allocated to the stack, we generate liveness info
  				 * for noref vars in registers in mono_spill_global_vars (), because
  				 * knowing that a register doesn't contain a ref allows us to mark its save
  				 * locations precisely.
  				 */
  				for (cindex = 0; cindex < gcfg->ncallsites; ++cindex)
  					if (gcfg->callsites [cindex]->liveness [i / 8] & (1 << (i % 8)))
  						set_reg_slot (gcfg, hreg, cindex, slot_type);
  			}
  
  			if (cfg->verbose_level > 1) {
  				printf ("\t%s %sreg %s(R%d)\n", slot_type_to_string (slot_type), is_arg ? "arg " : "", mono_arch_regname (hreg), vmv->vreg);
  			}
  
  			continue;
  		}
  
  		if (ins->opcode != OP_REGOFFSET)
  			continue;
  
  		if (ins->inst_offset % sizeof (mgreg_t) != 0)
  			continue;
  
  		if (is_arg && ins->inst_offset >= gcfg->max_offset)
  			/* In parent frame */
  			continue;
  
  		pos = fp_offset_to_slot (cfg, ins->inst_offset);
  
  		if (is_arg && ins->flags & MONO_INST_IS_DEAD) {
  			/* These do not get stored in the prolog */
  			set_slot_everywhere (gcfg, pos, SLOT_NOREF);
  
  			if (cfg->verbose_level > 1) {
  				printf ("\tdead arg at fp%s0x%x (slot = %d): %s\n", ins->inst_offset < 0 ? "-" : "+", (ins->inst_offset < 0) ? -(int)ins->inst_offset : (int)ins->inst_offset, pos, mono_type_full_name (ins->inst_vtype));
  			}
  			continue;
  		}
  
  		if (MONO_TYPE_ISSTRUCT (t)) {
  			int numbits = 0, j;
  			gsize *bitmap = NULL;
  			gboolean pin = FALSE;
  			int size;
  			int size_in_slots;
  			
  			if (ins->backend.is_pinvoke)
  				size = mono_class_native_size (ins->klass, NULL);
  			else
  				size = mono_class_value_size (ins->klass, NULL);
  			size_in_slots = ALIGN_TO (size, sizeof (mgreg_t)) / sizeof (mgreg_t);
  
  			if (!ins->klass->has_references) {
  				if (is_arg) {
  					for (j = 0; j < size_in_slots; ++j)
  						set_slot_everywhere (gcfg, pos + j, SLOT_NOREF);
  				}
  				continue;
  			}
  
  			if (ins->klass->generic_container || mono_class_is_open_constructed_type (t)) {
  				/* FIXME: Generic sharing */
  				pin = TRUE;
  			} else {
  				mono_class_compute_gc_descriptor (ins->klass);
  
  				bitmap = mono_gc_get_bitmap_for_descr (ins->klass->gc_descr, &numbits);
  				if (!bitmap)
  					pin = TRUE;
  
  				/*
  				 * Most vtypes are marked volatile because of the LDADDR instructions,
  				 * and they have no liveness information since they are decomposed
  				 * before the liveness pass. We emit OP_GC_LIVENESS_DEF instructions for
  				 * them during VZERO decomposition.
  				 */
  				if (!pc_offsets [vmv->vreg])
  					pin = TRUE;
  			}
  
  			if (ins->backend.is_pinvoke)
  				pin = TRUE;
  
  			if (cfg->verbose_level > 1)
  				printf ("\tvtype R%d at fp+0x%x-0x%x: %s\n", vmv->vreg, (int)ins->inst_offset, (int)(ins->inst_offset + (size / sizeof (mgreg_t))), mono_type_full_name (ins->inst_vtype));
  
  			if (bitmap) {
  				for (cindex = 0; cindex < gcfg->ncallsites; ++cindex) {
  					if (gcfg->callsites [cindex]->pc_offset > pc_offsets [vmv->vreg]) {
  						for (j = 0; j < numbits; ++j) {
  							if (bitmap [j / GC_BITS_PER_WORD] & ((gsize)1 << (j % GC_BITS_PER_WORD))) {
  								/* The descriptor is for the boxed object */
  								set_slot (gcfg, (pos + j - (sizeof (MonoObject) / sizeof (mgreg_t))), cindex, pin ? SLOT_PIN : SLOT_REF);
  							}
  						}
  					}
  				}
  
  				if (cfg->verbose_level > 1) {
  					for (j = 0; j < numbits; ++j) {
  						if (bitmap [j / GC_BITS_PER_WORD] & ((gsize)1 << (j % GC_BITS_PER_WORD)))
  							printf ("\t\t%s slot at 0x%x(fp) (slot = %d)\n", pin ? "pin" : "ref", (int)(ins->inst_offset + (j * sizeof (mgreg_t))), (int)(pos + j - (sizeof (MonoObject) / sizeof (mgreg_t))));
  					}
  				}
  			} else {
  				if (cfg->verbose_level > 1)
  					printf ("\t\tpinned\n");
  				for (j = 0; j < size_in_slots; ++j) {
  					set_slot_everywhere (gcfg, pos + j, SLOT_PIN);
  				}
  			}
  
  			g_free (bitmap);
  
  			continue;
  		}
  
  		if (!is_arg && (ins->inst_offset < gcfg->min_offset || ins->inst_offset >= gcfg->max_offset))
  			/* Vret addr etc. */
  			continue;
  
  		if (t->byref) {
  			if (is_arg) {
  				set_slot_everywhere (gcfg, pos, SLOT_PIN);
  			} else {
  				for (cindex = 0; cindex < gcfg->ncallsites; ++cindex)
  					if (gcfg->callsites [cindex]->liveness [i / 8] & (1 << (i % 8)))
  						set_slot (gcfg, pos, cindex, SLOT_PIN);
  			}
  			if (cfg->verbose_level > 1)
  				printf ("\tbyref at %s0x%x(fp) (R%d, slot = %d): %s\n", ins->inst_offset < 0 ? "-" : "", (ins->inst_offset < 0) ? -(int)ins->inst_offset : (int)ins->inst_offset, vmv->vreg, pos, mono_type_full_name (ins->inst_vtype));
  			continue;
  		}
  
  		/*
  		 * This is currently disabled, but could be enabled to debug crashes.
  		 */
  #if 0
  		if (t->type == MONO_TYPE_I) {
  			/*
  			 * Variables created in mono_handle_global_vregs have type I, but they
  			 * could hold GC refs since the vregs they were created from might not been
  			 * marked as holding a GC ref. So be conservative.
  			 */
  			set_slot_everywhere (gcfg, pos, SLOT_PIN);
  			continue;
  		}
  #endif
  
  		t = mini_type_get_underlying_type (NULL, t);
  
  		if (!MONO_TYPE_IS_REFERENCE (t)) {
  			set_slot_everywhere (gcfg, pos, SLOT_NOREF);
  			if (cfg->verbose_level > 1)
  				printf ("\tnoref at %s0x%x(fp) (R%d, slot = %d): %s\n", ins->inst_offset < 0 ? "-" : "", (ins->inst_offset < 0) ? -(int)ins->inst_offset : (int)ins->inst_offset, vmv->vreg, pos, mono_type_full_name (ins->inst_vtype));
  			continue;
  		}
  
  		/* 'this' is marked INDIRECT for gshared methods */
  		if (ins->flags & (MONO_INST_VOLATILE | MONO_INST_INDIRECT) && !is_this) {
  			/*
  			 * For volatile variables, treat them alive from the point they are
  			 * initialized in the first bblock until the end of the method.
  			 */
  			if (is_arg) {
  				set_slot_everywhere (gcfg, pos, SLOT_REF);
  			} else if (pc_offsets [vmv->vreg]) {
  				set_slot_in_range (gcfg, pos, 0, pc_offsets [vmv->vreg], SLOT_PIN);
  				set_slot_in_range (gcfg, pos, pc_offsets [vmv->vreg], cfg->code_size, SLOT_REF);
  			} else {
  				set_slot_everywhere (gcfg, pos, SLOT_PIN);
  			}
  			if (cfg->verbose_level > 1)
  				printf ("\tvolatile ref at %s0x%x(fp) (R%d, slot = %d): %s\n", ins->inst_offset < 0 ? "-" : "", (ins->inst_offset < 0) ? -(int)ins->inst_offset : (int)ins->inst_offset, vmv->vreg, pos, mono_type_full_name (ins->inst_vtype));
  			continue;
  		}
  
  		if (is_arg) {
  			/* Live for the whole method */
  			set_slot_everywhere (gcfg, pos, SLOT_REF);
  		} else {
  			for (cindex = 0; cindex < gcfg->ncallsites; ++cindex)
  				if (gcfg->callsites [cindex]->liveness [i / 8] & (1 << (i % 8)))
  					set_slot (gcfg, pos, cindex, SLOT_REF);
  		}
  
  		if (cfg->verbose_level > 1) {
  			printf ("\tref at %s0x%x(fp) (R%d, slot = %d): %s\n", ins->inst_offset < 0 ? "-" : "", (ins->inst_offset < 0) ? -(int)ins->inst_offset : (int)ins->inst_offset, vmv->vreg, pos, mono_type_full_name (ins->inst_vtype));
  		}
  	}
  
  	g_free (pc_offsets);
  }
  
  static int
  sp_offset_to_fp_offset (MonoCompile *cfg, int sp_offset)
  {
  	/* 
  	 * Convert a sp relative offset to a slot index. This is
  	 * platform specific.
  	 */
  #ifdef TARGET_AMD64
  	/* fp = sp + offset */
  	g_assert (cfg->frame_reg == AMD64_RBP);
  	return (- cfg->arch.sp_fp_offset + sp_offset);
  #else
  	NOT_IMPLEMENTED;
  	return -1;
  #endif
  }
  
  static GCSlotType
  type_to_gc_slot_type (MonoType *t)
  {
  	if (t->byref)
  		return SLOT_PIN;
  	t = mini_type_get_underlying_type (NULL, t);
  	if (MONO_TYPE_IS_REFERENCE (t))
  		return SLOT_REF;
  	else {
  		if (MONO_TYPE_ISSTRUCT (t)) {
  			MonoClass *klass = mono_class_from_mono_type (t);
  			if (!klass->has_references) {
  				return SLOT_NOREF;
  			} else {
  				// FIXME:
  				return SLOT_PIN;
  			}
  		}
  		return SLOT_NOREF;
  	}
  }
  
  static void
  process_param_area_slots (MonoCompile *cfg)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  	int i;
  	gboolean *is_param;
  
  	/*
  	 * These slots are used for passing parameters during calls. They are sp relative, not
  	 * fp relative, so they are harder to handle.
  	 */
  	if (cfg->flags & MONO_CFG_HAS_ALLOCA)
  		/* The distance between fp and sp is not constant */
  		return;
  
  	is_param = mono_mempool_alloc0 (cfg->mempool, gcfg->nslots * sizeof (gboolean));
  
  	for (i = 0; i < gcfg->ncallsites; ++i) {
  		GCCallSite *callsite = gcfg->callsites [i];
  		GSList *l;
  
  		for (l = callsite->param_slots; l; l = l->next) {
  			MonoInst *def = l->data;
  			int sp_offset = def->inst_offset;
  			int fp_offset = sp_offset_to_fp_offset (cfg, sp_offset);
  			int slot = fp_offset_to_slot (cfg, fp_offset);
  
  			g_assert (slot >= 0 && slot < gcfg->nslots);
  			is_param [slot] = TRUE;
  		}
  	}
  
  	/* All param area slots are noref by default */
  	for (i = 0; i < gcfg->nslots; ++i) {
  		if (is_param [i])
  			set_slot_everywhere (gcfg, i, SLOT_NOREF);
  	}
  
  	for (i = 0; i < gcfg->ncallsites; ++i) {
  		GCCallSite *callsite = gcfg->callsites [i];
  		GSList *l;
  
  		for (l = callsite->param_slots; l; l = l->next) {
  			MonoInst *def = l->data;
  			MonoType *t = def->inst_vtype;
  			int sp_offset = def->inst_offset;
  			int fp_offset = sp_offset_to_fp_offset (cfg, sp_offset);
  			int slot = fp_offset_to_slot (cfg, fp_offset);
  			GCSlotType type = type_to_gc_slot_type (t);
  
  			/* The slot is live between the def instruction and the call */
  			set_slot_in_range (gcfg, slot, def->backend.pc_offset, callsite->pc_offset + 1, type);
  			if (cfg->verbose_level > 1)
  				printf ("\t%s param area slot at %s0x%x(fp)=0x%x(sp) (slot = %d) [0x%x-0x%x]\n", slot_type_to_string (type), fp_offset >= 0 ? "+" : "-", ABS (fp_offset), sp_offset, slot, def->backend.pc_offset, callsite->pc_offset + 1);
  		}
  	}
  }
  
  static void
  process_finally_clauses (MonoCompile *cfg)
  {
  	MonoCompileGC *gcfg = cfg->gc_info;
  	GCCallSite **callsites;
  	int ncallsites;
  	gboolean has_finally;
  	int i, j, nslots, nregs;
  
  	ncallsites = gcfg->ncallsites;
  	nslots = gcfg->nslots;
  	nregs = gcfg->nregs;
  	callsites = gcfg->callsites;
  
  	/*
  	 * The calls to the finally clauses don't show up in the cfg. See
  	 * test_0_liveness_8 ().
  	 * Variables accessed inside the finally clause are already marked VOLATILE by
  	 * mono_liveness_handle_exception_clauses (). Variables not accessed inside the finally clause have
  	 * correct liveness outside the finally clause. So mark them PIN inside the finally clauses.
  	 */
  	has_finally = FALSE;
  	for (i = 0; i < cfg->header->num_clauses; ++i) {
  		MonoExceptionClause *clause = &cfg->header->clauses [i];
  
  		if (clause->flags == MONO_EXCEPTION_CLAUSE_FINALLY) {
  			has_finally = TRUE;
  		}
  	}
  	if (has_finally) {
  		if (cfg->verbose_level > 1)
  			printf ("\tMethod has finally clauses, pessimizing live ranges.\n");
  		for (j = 0; j < ncallsites; ++j) {
  			MonoBasicBlock *bb = callsites [j]->bb;
  			MonoExceptionClause *clause;
  			gboolean is_in_finally = FALSE;
  
  			for (i = 0; i < cfg->header->num_clauses; ++i) {
  				clause = &cfg->header->clauses [i];
  			   
  				if (MONO_OFFSET_IN_HANDLER (clause, bb->real_offset)) {
  					if (clause->flags == MONO_EXCEPTION_CLAUSE_FINALLY) {
  						is_in_finally = TRUE;
  						break;
  					}
  				}
  			}
  
  			if (is_in_finally) {
  				for (i = 0; i < nslots; ++i)
  					set_slot (gcfg, i, j, SLOT_PIN);
  				for (i = 0; i < nregs; ++i)
  					set_reg_slot (gcfg, i, j, SLOT_PIN);
  			}
  		}
  	}
  }
  
  static void
  compute_frame_size (MonoCompile *cfg)
  {
  	int i, locals_min_offset, locals_max_offset, cfa_min_offset, cfa_max_offset;
  	int min_offset, max_offset;
  	MonoCompileGC *gcfg = cfg->gc_info;
  	MonoMethodSignature *sig = mono_method_signature (cfg->method);
  	GSList *l;
  
  	/* Compute min/max offsets from the fp */
  
  	/* Locals */
  #if defined(TARGET_AMD64) || defined(TARGET_X86)
  	locals_min_offset = ALIGN_TO (cfg->locals_min_stack_offset, sizeof (mgreg_t));
  	locals_max_offset = cfg->locals_max_stack_offset;
  #else
  	/* min/max stack offset needs to be computed in mono_arch_allocate_vars () */
  	NOT_IMPLEMENTED;
  #endif
  
  	locals_min_offset = ALIGN_TO (locals_min_offset, sizeof (mgreg_t));
  	locals_max_offset = ALIGN_TO (locals_max_offset, sizeof (mgreg_t));
  
  	min_offset = locals_min_offset;
  	max_offset = locals_max_offset;
  
  	/* Arguments */
  	for (i = 0; i < sig->param_count + sig->hasthis; ++i) {
  		MonoInst *ins = cfg->args [i];
  
  		if (ins->opcode == OP_REGOFFSET)
  			min_offset = MIN (min_offset, ins->inst_offset);
  	}
  
  	/* Cfa slots */
  	g_assert (cfg->frame_reg == cfg->cfa_reg);
  	g_assert (cfg->cfa_offset > 0);
  	cfa_min_offset = 0;
  	cfa_max_offset = cfg->cfa_offset;
  
  	min_offset = MIN (min_offset, cfa_min_offset);
  	max_offset = MAX (max_offset, cfa_max_offset);
  
  	/* Fp relative slots */
  	for (l = gcfg->stack_slots_from_fp; l; l = l->next) {
  		gint data = GPOINTER_TO_INT (l->data);
  		int offset = data >> 16;
  
  		min_offset = MIN (min_offset, offset);
  	}
  
  	/* Spill slots */
  	if (!(cfg->flags & MONO_CFG_HAS_SPILLUP)) {
  		int stack_offset = ALIGN_TO (cfg->stack_offset, sizeof (mgreg_t));
  		min_offset = MIN (min_offset, (-stack_offset));
  	}
  
  	/* Param area slots */
  #ifdef TARGET_AMD64
  	min_offset = MIN (min_offset, -cfg->arch.sp_fp_offset);
  #endif
  
  	gcfg->min_offset = min_offset;
  	gcfg->max_offset = max_offset;
  	gcfg->locals_min_offset = locals_min_offset;
  	gcfg->locals_max_offset = locals_max_offset;
  }
  
  static void
  init_gcfg (MonoCompile *cfg)
  {
  	int i, nregs, nslots;
  	MonoCompileGC *gcfg = cfg->gc_info;
  	GCCallSite **callsites;
  	int ncallsites;
  	MonoBasicBlock *bb;
  	GSList *l;
  
  	/*
  	 * Collect callsites
  	 */
  	ncallsites = 0;
  	for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  		ncallsites += g_slist_length (bb->gc_callsites);
  	}
  	callsites = mono_mempool_alloc0 (cfg->mempool, ncallsites * sizeof (GCCallSite*));
  	i = 0;
  	for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
  		for (l = bb->gc_callsites; l; l = l->next)
  			callsites [i++] = l->data;
  	}
  
  	/* The callsites should already be ordered by pc offset */
  	for (i = 1; i < ncallsites; ++i)
  		g_assert (callsites [i - 1]->pc_offset < callsites [i]->pc_offset);
  
  	/*
  	 * The stack frame looks like this:
  	 *
  	 * <fp + max_offset> == cfa ->  <end of previous frame>
  	 *                              <other stack slots>
  	 *                              <locals>
  	 *                              <other stack slots>
  	 * fp + min_offset          ->
  	 * ...
  	 * fp                       ->
  	 */
  
  	if (cfg->verbose_level > 1)
  		printf ("GC Map for %s: 0x%x-0x%x\n", mono_method_full_name (cfg->method, TRUE), gcfg->min_offset, gcfg->max_offset);
  
  	nslots = (gcfg->max_offset - gcfg->min_offset) / sizeof (mgreg_t);
  	nregs = NREGS;
  
  	gcfg->nslots = nslots;
  	gcfg->nregs = nregs;
  	gcfg->callsites = callsites;
  	gcfg->ncallsites = ncallsites;
  	gcfg->stack_bitmap_width = ALIGN_TO (nslots, 8) / 8;
  	gcfg->reg_bitmap_width = ALIGN_TO (nregs, 8) / 8;
  	gcfg->stack_ref_bitmap = mono_mempool_alloc0 (cfg->mempool, gcfg->stack_bitmap_width * ncallsites);
  	gcfg->stack_pin_bitmap = mono_mempool_alloc0 (cfg->mempool, gcfg->stack_bitmap_width * ncallsites);
  	gcfg->reg_ref_bitmap = mono_mempool_alloc0 (cfg->mempool, gcfg->reg_bitmap_width * ncallsites);
  	gcfg->reg_pin_bitmap = mono_mempool_alloc0 (cfg->mempool, gcfg->reg_bitmap_width * ncallsites);
  
  	/* All slots start out as PIN */
  	memset (gcfg->stack_pin_bitmap, 0xff, gcfg->stack_bitmap_width * ncallsites);
  	for (i = 0; i < nregs; ++i) {
  		/*
  		 * By default, registers are NOREF.
  		 * It is possible for a callee to save them before being defined in this method,
  		 * but the saved value is dead too, so it doesn't need to be marked.
  		 */
  		if ((cfg->used_int_regs & (1 << i)))
  			set_reg_slot_everywhere (gcfg, i, SLOT_NOREF);
  	}
  }
  
  static void
  create_map (MonoCompile *cfg)
  {
  	GCMap *map;
  	int i, j, nregs, nslots, nref_regs, npin_regs, alloc_size, bitmaps_size, bitmaps_offset;
  	int ntypes [16];
  	int stack_bitmap_width, stack_bitmap_size, reg_ref_bitmap_width, reg_ref_bitmap_size;
  	int reg_pin_bitmap_width, reg_pin_bitmap_size, bindex;
  	int start, end;
  	gboolean has_ref_slots, has_pin_slots, has_ref_regs, has_pin_regs;
  	MonoCompileGC *gcfg = cfg->gc_info;
  	GCCallSite **callsites;
  	int ncallsites;
  	guint8 *bitmap, *bitmaps;
  	guint32 reg_ref_mask, reg_pin_mask;
  
  	ncallsites = gcfg->ncallsites;
  	nslots = gcfg->nslots;
  	nregs = gcfg->nregs;
  	callsites = gcfg->callsites;
  
  	/* 
  	 * Compute the real size of the bitmap i.e. ignore NOREF columns at the beginning and at
  	 * the end. Also, compute whenever the map needs ref/pin bitmaps, and collect stats.
  	 */
  	has_ref_slots = FALSE;
  	has_pin_slots = FALSE;
  	start = -1;
  	end = -1;
  	memset (ntypes, 0, sizeof (ntypes));
  	for (i = 0; i < nslots; ++i) {
  		gboolean has_ref = FALSE;
  		gboolean has_pin = FALSE;
  
  		for (j = 0; j < ncallsites; ++j) {
  			if (get_bit (gcfg->stack_pin_bitmap, gcfg->stack_bitmap_width, j, i))
  				has_pin = TRUE;
  			if (get_bit (gcfg->stack_ref_bitmap, gcfg->stack_bitmap_width, j, i))
  				has_ref = TRUE;
  		}
  
  		if (has_ref)
  			has_ref_slots = TRUE;
  		if (has_pin)
  			has_pin_slots = TRUE;
  
  		if (has_ref)
  			ntypes [SLOT_REF] ++;
  		else if (has_pin)
  			ntypes [SLOT_PIN] ++;
  		else
  			ntypes [SLOT_NOREF] ++;
  
  		if (has_ref || has_pin) {
  			if (start == -1)
  				start = i;
  			end = i + 1;
  		}
  	}
  	if (start == -1) {
  		start = end = nslots;
  	} else {
  		g_assert (start != -1);
  		g_assert (start < end);
  	}
  
  	has_ref_regs = FALSE;
  	has_pin_regs = FALSE;
  	reg_ref_mask = 0;
  	reg_pin_mask = 0;
  	nref_regs = 0;
  	npin_regs = 0;
  	for (i = 0; i < nregs; ++i) {
  		gboolean has_ref = FALSE;
  		gboolean has_pin = FALSE;
  
  		if (!(cfg->used_int_regs & (1 << i)))
  			continue;
  
  		for (j = 0; j < ncallsites; ++j) {
  			if (get_bit (gcfg->reg_ref_bitmap, gcfg->reg_bitmap_width, j, i)) {
  				has_ref = TRUE;
  				break;
  			}
  		}
  		for (j = 0; j < ncallsites; ++j) {
  			if (get_bit (gcfg->reg_pin_bitmap, gcfg->reg_bitmap_width, j, i)) {
  				has_pin = TRUE;
  				break;
  			}
  		}
  
  		if (has_ref) {
  			reg_ref_mask |= (1 << i);
  			has_ref_regs = TRUE;
  			nref_regs ++;
  		}
  		if (has_pin) {
  			reg_pin_mask |= (1 << i);
  			has_pin_regs = TRUE;
  			npin_regs ++;
  		}
  	}
  
  	if (cfg->verbose_level > 1)
  		printf ("Slots: %d Start: %d End: %d Refs: %d NoRefs: %d Pin: %d Callsites: %d\n", nslots, start, end, ntypes [SLOT_REF], ntypes [SLOT_NOREF], ntypes [SLOT_PIN], ncallsites);
  
  	/* Create the GC Map */
  
  	stack_bitmap_width = ALIGN_TO (end - start, 8) / 8;
  	stack_bitmap_size = stack_bitmap_width * ncallsites;
  	reg_ref_bitmap_width = ALIGN_TO (nref_regs, 8) / 8;
  	reg_ref_bitmap_size = reg_ref_bitmap_width * ncallsites;
  	reg_pin_bitmap_width = ALIGN_TO (npin_regs, 8) / 8;
  	reg_pin_bitmap_size = reg_pin_bitmap_width * ncallsites;
  	bitmaps_size = (has_ref_slots ? stack_bitmap_size : 0) + (has_pin_slots ? stack_bitmap_size : 0) + (has_ref_regs ? reg_ref_bitmap_size : 0) + (has_pin_regs ? reg_pin_bitmap_size : 0);
  	
  	map = mono_mempool_alloc0 (cfg->mempool, sizeof (GCMap));
  
  	map->frame_reg = cfg->frame_reg;
  	map->start_offset = gcfg->min_offset;
  	map->end_offset = gcfg->min_offset + (nslots * sizeof (mgreg_t));
  	map->map_offset = start * sizeof (mgreg_t);
  	map->nslots = end - start;
  	map->has_ref_slots = has_ref_slots;
  	map->has_pin_slots = has_pin_slots;
  	map->has_ref_regs = has_ref_regs;
  	map->has_pin_regs = has_pin_regs;
  	g_assert (nregs < 32);
  	map->used_int_regs = cfg->used_int_regs;
  	map->reg_ref_mask = reg_ref_mask;
  	map->reg_pin_mask = reg_pin_mask;
  	map->nref_regs = nref_regs;
  	map->npin_regs = npin_regs;
  
  	bitmaps = mono_mempool_alloc0 (cfg->mempool, bitmaps_size);
  
  	bitmaps_offset = 0;
  	if (has_ref_slots) {
  		map->stack_ref_bitmap_offset = bitmaps_offset;
  		bitmaps_offset += stack_bitmap_size;
  
  		bitmap = &bitmaps [map->stack_ref_bitmap_offset];
  		for (i = 0; i < nslots; ++i) {
  			for (j = 0; j < ncallsites; ++j) {
  				if (get_bit (gcfg->stack_ref_bitmap, gcfg->stack_bitmap_width, j, i))
  					set_bit (bitmap, stack_bitmap_width, j, i - start);
  			}
  		}
  	}
  	if (has_pin_slots) {
  		map->stack_pin_bitmap_offset = bitmaps_offset;
  		bitmaps_offset += stack_bitmap_size;
  
  		bitmap = &bitmaps [map->stack_pin_bitmap_offset];
  		for (i = 0; i < nslots; ++i) {
  			for (j = 0; j < ncallsites; ++j) {
  				if (get_bit (gcfg->stack_pin_bitmap, gcfg->stack_bitmap_width, j, i))
  					set_bit (bitmap, stack_bitmap_width, j, i - start);
  			}
  		}
  	}
  	if (has_ref_regs) {
  		map->reg_ref_bitmap_offset = bitmaps_offset;
  		bitmaps_offset += reg_ref_bitmap_size;
  
  		bitmap = &bitmaps [map->reg_ref_bitmap_offset];
  		bindex = 0;
  		for (i = 0; i < nregs; ++i) {
  			if (reg_ref_mask & (1 << i)) {
  				for (j = 0; j < ncallsites; ++j) {
  					if (get_bit (gcfg->reg_ref_bitmap, gcfg->reg_bitmap_width, j, i))
  						set_bit (bitmap, reg_ref_bitmap_width, j, bindex);
  				}
  				bindex ++;
  			}
  		}
  	}
  	if (has_pin_regs) {
  		map->reg_pin_bitmap_offset = bitmaps_offset;
  		bitmaps_offset += reg_pin_bitmap_size;
  
  		bitmap = &bitmaps [map->reg_pin_bitmap_offset];
  		bindex = 0;
  		for (i = 0; i < nregs; ++i) {
  			if (reg_pin_mask & (1 << i)) {
  				for (j = 0; j < ncallsites; ++j) {
  					if (get_bit (gcfg->reg_pin_bitmap, gcfg->reg_bitmap_width, j, i))
  						set_bit (bitmap, reg_pin_bitmap_width, j, bindex);
  				}
  				bindex ++;
  			}
  		}
  	}
  
  	/* Call sites */
  	map->ncallsites = ncallsites;
  	if (cfg->code_len < 256)
  		map->callsite_entry_size = 1;
  	else if (cfg->code_len < 65536)
  		map->callsite_entry_size = 2;
  	else
  		map->callsite_entry_size = 4;
  
  	/* Encode the GC Map */
  	{
  		guint8 buf [256];
  		guint8 *endbuf;
  		GCEncodedMap *emap;
  		int encoded_size;
  		guint8 *p;
  
  		encode_gc_map (map, buf, &endbuf);
  		g_assert (endbuf - buf < 256);
  
  		encoded_size = endbuf - buf;
  		alloc_size = sizeof (GCEncodedMap) + ALIGN_TO (encoded_size, map->callsite_entry_size) + (map->callsite_entry_size * map->ncallsites) + bitmaps_size;
  
  		emap = mono_domain_alloc0 (cfg->domain, alloc_size);
  		//emap->ref_slots = map->ref_slots;
  
  		/* Encoded fixed fields */
  		p = &emap->encoded [0];
  		//emap->encoded_size = encoded_size;
  		memcpy (p, buf, encoded_size);
  		p += encoded_size;
  
  		/* Callsite table */
  		p = (guint8*)ALIGN_TO ((mgreg_t)p, map->callsite_entry_size);
  		if (map->callsite_entry_size == 1) {
  			guint8 *offsets = p;
  			for (i = 0; i < ncallsites; ++i)
  				offsets [i] = callsites [i]->pc_offset;
  			stats.gc_callsites8_size += ncallsites * sizeof (guint8);
  		} else if (map->callsite_entry_size == 2) {
  			guint16 *offsets = (guint16*)p;
  			for (i = 0; i < ncallsites; ++i)
  				offsets [i] = callsites [i]->pc_offset;
  			stats.gc_callsites16_size += ncallsites * sizeof (guint16);
  		} else {
  			guint32 *offsets = (guint32*)p;
  			for (i = 0; i < ncallsites; ++i)
  				offsets [i] = callsites [i]->pc_offset;
  			stats.gc_callsites32_size += ncallsites * sizeof (guint32);
  		}
  		p += ncallsites * map->callsite_entry_size;
  
  		/* Bitmaps */
  		memcpy (p, bitmaps, bitmaps_size);
  		p += bitmaps_size;
  
  		g_assert ((guint8*)p - (guint8*)emap <= alloc_size);
  
  		stats.gc_maps_size += alloc_size;
  		stats.gc_callsites_size += ncallsites * map->callsite_entry_size;
  		stats.gc_bitmaps_size += bitmaps_size;
  		stats.gc_map_struct_size += sizeof (GCEncodedMap) + encoded_size;
  
  		cfg->jit_info->gc_info = emap;
  
  		cfg->gc_map = (guint8*)emap;
  		cfg->gc_map_size = alloc_size;
  	}
  
  	stats.all_slots += nslots;
  	stats.ref_slots += ntypes [SLOT_REF];
  	stats.noref_slots += ntypes [SLOT_NOREF];
  	stats.pin_slots += ntypes [SLOT_PIN];
  }
  
  void
  mini_gc_create_gc_map (MonoCompile *cfg)
  {
  	if (!cfg->compute_gc_maps)
  		return;
  
  	/*
  	 * During marking, all frames except the top frame are at a call site, and we mark the
  	 * top frame conservatively. This means that we only need to compute and record
  	 * GC maps for call sites.
  	 */
  
  	if (!(cfg->comp_done & MONO_COMP_LIVENESS))
  		/* Without liveness info, the live ranges are not precise enough */
  		return;
  
  	mono_analyze_liveness_gc (cfg);
  
  	compute_frame_size (cfg);
  
  	init_gcfg (cfg);
  
  	process_spill_slots (cfg);
  	process_other_slots (cfg);
  	process_param_area_slots (cfg);
  	process_variables (cfg);
  	process_finally_clauses (cfg);
  
  	create_map (cfg);
  }
  
  static void
  parse_debug_options (void)
  {
  	char **opts, **ptr;
  	char *env;
  
  	env = getenv ("MONO_GCMAP_DEBUG");
  	if (!env)
  		return;
  
  	opts = g_strsplit (env, ",", -1);
  	for (ptr = opts; ptr && *ptr; ptr ++) {
  		/* No options yet */
  		fprintf (stderr, "Invalid format for the MONO_GCMAP_DEBUG env variable: '%s'\n", env);
  		exit (1);
  	}
  	g_strfreev (opts);
  }
  
  void
  mini_gc_init (void)
  {
  	MonoGCCallbacks cb;
  
  	memset (&cb, 0, sizeof (cb));
  	cb.thread_attach_func = thread_attach_func;
  	cb.thread_detach_func = thread_detach_func;
  	cb.thread_suspend_func = thread_suspend_func;
  	/* Comment this out to disable precise stack marking */
  	cb.thread_mark_func = thread_mark_func;
  	mono_gc_set_gc_callbacks (&cb);
  
  	logfile = mono_sgen_get_logfile ();
  
  	parse_debug_options ();
  
  	mono_counters_register ("GC Maps size",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_maps_size);
  	mono_counters_register ("GC Call Sites size",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_callsites_size);
  	mono_counters_register ("GC Bitmaps size",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_bitmaps_size);
  	mono_counters_register ("GC Map struct size",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_map_struct_size);
  	mono_counters_register ("GC Call Sites encoded using 8 bits",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_callsites8_size);
  	mono_counters_register ("GC Call Sites encoded using 16 bits",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_callsites16_size);
  	mono_counters_register ("GC Call Sites encoded using 32 bits",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.gc_callsites32_size);
  
  	mono_counters_register ("GC Map slots (all)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.all_slots);
  	mono_counters_register ("GC Map slots (ref)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.ref_slots);
  	mono_counters_register ("GC Map slots (noref)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.noref_slots);
  	mono_counters_register ("GC Map slots (pin)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.pin_slots);
  
  	mono_counters_register ("GC TLS Data size",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.tlsdata_size);
  
  	mono_counters_register ("Stack space scanned (all)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned_stacks);
  	mono_counters_register ("Stack space scanned (native)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned_native);
  	mono_counters_register ("Stack space scanned (other)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned_other);
  	mono_counters_register ("Stack space scanned (using GC Maps)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned);
  	mono_counters_register ("Stack space scanned (precise)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned_precisely);
  	mono_counters_register ("Stack space scanned (pin)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned_conservatively);
  	mono_counters_register ("Stack space scanned (pin registers)",
  							MONO_COUNTER_GC | MONO_COUNTER_INT, &stats.scanned_registers);
  }
  
  #else
  
  void
  mini_gc_init (void)
  {
  }
  
  static void
  mini_gc_init_gc_map (MonoCompile *cfg)
  {
  }
  
  void
  mini_gc_create_gc_map (MonoCompile *cfg)
  {
  }
  
  void
  mini_gc_set_slot_type_from_fp (MonoCompile *cfg, int slot_offset, GCSlotType type)
  {
  }
  
  void
  mini_gc_set_slot_type_from_cfa (MonoCompile *cfg, int slot_offset, GCSlotType type)
  {
  }
  
  #endif
  
  /*
   * mini_gc_init_cfg:
   *
   *   Set GC specific options in CFG.
   */
  void
  mini_gc_init_cfg (MonoCompile *cfg)
  {
  	if (mono_gc_is_moving ()) {
  		cfg->disable_ref_noref_stack_slot_share = TRUE;
  		cfg->gen_write_barriers = TRUE;
  	}
  
  	mini_gc_init_gc_map (cfg);
  }
  
  /*
   * Problems with the current code:
   * - the stack walk is slow
   * - vtypes/refs used in EH regions are treated conservatively
   * - if the code is finished, less pinning will be done, causing problems because
   *   we promote all surviving objects to old-gen.
   * - the unwind code can't handle a method stopped inside a finally region, it thinks the caller is
   *   another method, but in reality it is either the exception handling code or the CALL_HANDLER opcode.
   *   This manifests in "Unable to find ip offset x in callsite list" assertions.
   * - the unwind code also can't handle frames which are in the epilog, since the unwind info is not
   *   precise there.
   */
  
  /*
   * Ideas for creating smaller GC maps:
   * - remove empty columns from the bitmaps. This requires adding a mask bit array for
   *   each bitmap.
   * - merge reg and stack slot bitmaps, so the unused bits at the end of the reg bitmap are
   *   not wasted.
   * - if the bitmap width is not a multiple of 8, the remaining bits are wasted.
   * - group ref and non-ref stack slots together in mono_allocate_stack_slots ().
   * - add an index for the callsite table so that each entry can be encoded as a 1 byte difference
   *   from an index entry.
   */
  