Revert "memory: Change the gc into a refcounter, for speed reasons. [O. Galibert]"

This reverts commit 5deef5b2c6fabdea8cd45ccf71c99f56940e88a2.

Broken, sorry.

src/emu/memory.c

@@ -837,6 +837,7 @@ protected:
 	// table population/depopulation
 	void populate_range_mirrored(offs_t bytestart, offs_t byteend, offs_t bytemirror, UINT8 handler);
 	void populate_range(offs_t bytestart, offs_t byteend, UINT8 handler);
+	void depopulate_unused();
 
 	// subtable management
 	UINT8 subtable_alloc();
@@ -873,29 +874,7 @@ protected:
 	static UINT8			s_watchpoint_table[1 << LEVEL1_BITS];
 
 private:
-	int handler_refcount[SUBTABLE_BASE-STATIC_COUNT];
-	UINT8 handler_next_free[SUBTABLE_BASE-STATIC_COUNT];
-	UINT8 handler_free;
 	UINT8 get_free_handler();
-
-	void handler_ref(UINT8 entry, int count)
-	{
-		assert(entry < SUBTABLE_BASE);
-		if (entry >= STATIC_COUNT)
-			handler_refcount[entry - STATIC_COUNT] += count;
-	}
-
-	void handler_unref(UINT8 entry)
-	{
-		assert(entry < SUBTABLE_BASE);
-		if (entry >= STATIC_COUNT)
-			if (! --handler_refcount[entry - STATIC_COUNT])
-			{
-				handler(entry).deconfigure();
-				handler_next_free[entry - STATIC_COUNT] = handler_free;
-				handler_free = entry;
-			}
-	}
 };
 
 
@@ -3228,15 +3207,6 @@ address_table::address_table(address_space &space, bool large)
 
 	// initialize everything to unmapped
 	memset(m_table, STATIC_UNMAP, 1 << LEVEL1_BITS);
-
-	// initialize the handlers freelist
-	for (int i=0; i != SUBTABLE_BASE-STATIC_COUNT-1; i++)
-		handler_next_free[i] = i+STATIC_COUNT+1;
-	handler_next_free[SUBTABLE_BASE-STATIC_COUNT-1] = STATIC_INVALID;
-	handler_free = STATIC_COUNT;
-
-	// initialize the handlers refcounts
-	memset(handler_refcount, 0, sizeof(handler_refcount));
 }
 
 
@@ -3284,12 +3254,18 @@ void address_table::map_range(offs_t addrstart, offs_t addrend, offs_t addrmask,
 
 UINT8 address_table::get_free_handler()
 {
-	if (handler_free == STATIC_INVALID)
+	// scan all possible assigned entries for something unpopulated
-		throw emu_fatalerror("Out of handler entries in address table");
+	for (UINT8 scanentry = STATIC_COUNT; scanentry < SUBTABLE_BASE; scanentry++)
+		if (!handler(scanentry).populated())
+			return scanentry;
 
-	UINT8 handler = handler_free;
+	// if we didn't find anything, find something to depopulate and try again
-	handler_free = handler_next_free[handler - STATIC_COUNT];
+	depopulate_unused();
-	return handler;
+	for (UINT8 scanentry = STATIC_COUNT; scanentry < SUBTABLE_BASE; scanentry++)
+		if (!handler(scanentry).populated())
+			return scanentry;
+
+	throw emu_fatalerror("Out of handler entries in address table");
 }
 
 
@@ -3443,24 +3419,13 @@ void address_table::populate_range(offs_t bytestart, offs_t byteend, UINT8 handl
 		// if the start and stop end within the same block, handle that
 		if (l1start == l1stop)
 		{
-			for (int i = l2start; i <= l2stop; i++)
+			memset(&subtable[l2start], handlerindex, l2stop - l2start + 1);
-			{
-				handler_unref(subtable[i]);
-				subtable[i] = handlerindex;
-			}
-			handler_ref(handlerindex, l2stop-l2start+1);
 			subtable_close(l1start);
 			return;
 		}
 
 		// otherwise, fill until the end
-		int max = 1 << level2_bits();
+		memset(&subtable[l2start], handlerindex, (1 << level2_bits()) - l2start);
-		for (int i = l2start; i < max; i++)
-		{
-			handler_unref(subtable[i]);
-			subtable[i] = handlerindex;
-		}
-		handler_ref(handlerindex, max - l2start);
 		subtable_close(l1start);
 		if (l1start != (offs_t)~0)
 			l1start++;
@@ -3472,12 +3437,7 @@ void address_table::populate_range(offs_t bytestart, offs_t byteend, UINT8 handl
 		UINT8 *subtable = subtable_open(l1stop);
 
 		// fill from the beginning
-		for (int i = 0; i <= l2stop; i++)
+		memset(&subtable[0], handlerindex, l2stop + 1);
-		{
-			handler_unref(subtable[i]);
-			subtable[i] = handlerindex;
-		}
-		handler_ref(handlerindex, l2stop+1);
 		subtable_close(l1stop);
 
 		// if the start and stop end within the same block, handle that
@@ -3490,22 +3450,11 @@ void address_table::populate_range(offs_t bytestart, offs_t byteend, UINT8 handl
 	// now fill in the middle tables
 	for (offs_t l1index = l1start; l1index <= l1stop; l1index++)
 	{
-		UINT8 subindex = m_table[l1index];
-
 		// if we have a subtable here, release it
-		if (m_table[l1index] >= SUBTABLE_BASE) {
+		if (m_table[l1index] >= SUBTABLE_BASE)
-			UINT8 *subtable = subtable_open(subindex);
+			subtable_release(m_table[l1index]);
-			int max = 1 << level2_bits();
-			for (int i = l2start; i < max; i++)
-				handler_unref(subtable[i]);
-			subtable_close(subindex);
-			subtable_release(subindex);
-		} else
-			handler_unref(subindex);
-
 		m_table[l1index] = handlerindex;
 	}
-	handler_ref(handlerindex, l1stop - l1start + 1);
 }
 
 
@@ -3594,6 +3543,41 @@ void address_table::populate_range_mirrored(offs_t bytestart, offs_t byteend, of
 }
 
 
+//-------------------------------------------------
+//  depopulate_unused - scan the table and
+//  eliminate entries that are no longer used
+//-------------------------------------------------
+
+void address_table::depopulate_unused()
+{
+	bool used[SUBTABLE_BASE - STATIC_COUNT];
+	memset(used, 0, sizeof(used));
+
+	for (int level1 = 0; level1 != 1 << LEVEL1_BITS; level1++)
+	{
+		UINT8 l1_entry = m_table[level1];
+		if (l1_entry >= SUBTABLE_BASE)
+		{
+			assert(m_large);
+			const UINT8 *subtable = subtable_ptr(l1_entry);
+			for (int level2 = 0; level2 != 1 << LEVEL2_BITS; level2++)
+			{
+				UINT8 l2_entry = subtable[level2];
+				assert(l2_entry < SUBTABLE_BASE);
+				if (l2_entry >= STATIC_COUNT)
+					used[l2_entry - STATIC_COUNT] = true;
+			}
+		}
+		else if (l1_entry >= STATIC_COUNT)
+			used[l1_entry - STATIC_COUNT] = true;
+	}
+
+	for (int slot=0; slot != SUBTABLE_BASE - STATIC_COUNT; slot++)
+		if (!used[slot])
+			handler(slot + STATIC_COUNT).deconfigure();
+}
+
+
 //-------------------------------------------------
 //  derive_range - look up the entry for a memory
 //  range, and then compute the extent of that