Add the +t emulator option to change the maximum number of atoms

It is now possible to increase or decrease the maximum number of atoms
the VM can handle. The default value is 1048576 (1024*1024).

erts/doc/src/erl.xml

@@ -798,6 +798,11 @@
           Valid range is 4-8192 kilowords. The default stack size
           is OS dependent.</p>
       </item>
+      <tag><c><![CDATA[+t size]]></c></tag>
+      <item>
+        <marker id="+t"></marker>
+        <p>Set the maximum number of atoms the VM can handle. Default is 1048576.</p>
+      </item>
       <tag><c><![CDATA[+T Level]]></c></tag>
       <item>
         <marker id="+T"></marker>

erts/emulator/beam/atom.c

@@ -322,7 +322,7 @@ init_atom_table(void)
     text_list = NULL;
 
     erts_index_init(ERTS_ALC_T_ATOM_TABLE, &erts_atom_table,
-		    "atom_tab", ATOM_SIZE, ATOM_LIMIT, f);
+		    "atom_tab", ATOM_SIZE, erts_atom_table_size, f);
     more_atom_space();
 
     /* Ordinary atoms */

erts/emulator/beam/atom.h

@@ -28,6 +28,17 @@
 
 #define MAX_ATOM_LENGTH 255
 #define ATOM_LIMIT (1024*1024)
+#define MIN_ATOM_TABLE_SIZE 8192
+
+#ifndef ARCH_32
+/* Internal atom cache needs MAX_ATOM_TABLE_SIZE to be less than an
+   unsigned 32 bit integer. See external.c(erts_encode_ext_dist_header_setup)
+   for more details. */
+#define MAX_ATOM_TABLE_SIZE ((MAX_ATOM_INDEX + 1 < (1UL << 32)) ? MAX_ATOM_INDEX + 1 : (1UL << 32))
+#else
+#define MAX_ATOM_TABLE_SIZE (MAX_ATOM_INDEX + 1)
+#endif
+
 
 /*
  * Atom entry.

erts/emulator/beam/erl_init.c

@@ -119,6 +119,8 @@ int erts_disable_tolerant_timeofday; /* Time correction can be disabled it is
 				      * not and/or it is too slow.
 				      */
 
+int erts_atom_table_size = ATOM_LIMIT;	/* Maximum number of atoms */
+
 int erts_modified_timing_level;
 
 int erts_no_crash_dump = 0;	/* Use -d to suppress crash dump. */
@@ -569,6 +571,10 @@ void erts_usage(void)
     erts_fprintf(stderr, "            schedulers online (n2), valid range for both\n");
     erts_fprintf(stderr, "            numbers are [1-%d]\n",
 		 ERTS_MAX_NO_OF_SCHEDULERS);
+    erts_fprintf(stderr, "-t size     set the maximum number of atoms the "
+			 "emulator can handle\n");
+    erts_fprintf(stderr, "            valid range is [%d-%d]\n",
+		 MIN_ATOM_TABLE_SIZE, MAX_ATOM_TABLE_SIZE);
     erts_fprintf(stderr, "-T number   set modified timing level,\n");
     erts_fprintf(stderr, "            valid range is [0-%d]\n",
 		 ERTS_MODIFIED_TIMING_LEVELS-1);
@@ -1140,6 +1146,22 @@ erl_start(int argc, char **argv)
 	    }
 	    break;
 	}
+	case 't':
+	    /* set atom table size */
+	    arg = get_arg(argv[i]+2, argv[i+1], &i);
+	    errno = 0;
+	    erts_atom_table_size = strtol(arg, NULL, 10);
+	    if (errno != 0 ||
+		erts_atom_table_size < MIN_ATOM_TABLE_SIZE ||
+		erts_atom_table_size > MAX_ATOM_TABLE_SIZE) {
+		erts_fprintf(stderr, "bad atom table size %s\n", arg);
+		erts_usage();
+	    }
+	    VERBOSE(DEBUG_SYSTEM,
+                    ("setting maximum number of atoms to %d\n",
+		     erts_atom_table_size));
+	    break;
+
 	case 'T' :
 	    arg = get_arg(argv[i]+2, argv[i+1], &i);
 	    errno = 0;

erts/emulator/beam/erl_vm.h

@@ -181,6 +181,8 @@ extern int num_instructions;	/* Number of instruction in opc[]. */
 extern int H_MIN_SIZE;		/* minimum (heap + stack) */
 extern int BIN_VH_MIN_SIZE;	/* minimum virtual (bin) heap */
 
+extern int erts_atom_table_size;/* Atom table size */
+
 #define ORIG_CREATION 0
 
 /* macros for extracting bytes from uint16's */

erts/emulator/beam/external.c

@@ -271,11 +271,8 @@ erts_encode_ext_dist_header_size(ErtsAtomCacheMap *acmp)
 
 byte *erts_encode_ext_dist_header_setup(byte *ctl_ext, ErtsAtomCacheMap *acmp)
 {
-#ifndef ARCH_32
-#if ATOM_LIMIT >= (1UL << 32)
-#error "ATOM_LIMIT too large for interal atom cache update instructions. New instructions needed."
-#endif
-#endif
+    /* Maximum number of atom must be less than the maximum of a 32 bits
+       unsigned integer. Check is done in erl_init.c, erl_start function. */
     if (!acmp)
 	return ctl_ext;
     else {

erts/etc/common/erlexec.c

@@ -794,6 +794,7 @@ int main(int argc, char **argv)
 		  case 'i':
 		  case 'P':
 		  case 'S':
+		  case 't':
 		  case 'T':
 		  case 'R':
 		  case 'W':