simplify maxtick parsing in both the python and the c++.

configs/common/Simulation.py:
    simplify maxtick code a little bit - instead of checking for -1, just set it at MaxTick.
src/python/m5/__init__.py:
    make a new m5 param called MaxTick.
src/sim/host.hh:
    fix the M5 def. of MaxTick
src/sim/main.cc:
    Simplify the MaxTick/num_cycles parsing within main.cc

--HG--
extra : convert_revision : f800addfbc1323591c2e05b892276b439b671668

src/python/m5/__init__.py

@@ -39,6 +39,9 @@ from cc_main import simulate, SimLoopExitEvent
 # import the m5 compile options
 import defines
 
+# define a MaxTick parameter
+MaxTick = 2**63 - 1
+
 # define this here so we can use it right away if necessary
 def panic(string):
     print >>sys.stderr, 'panic:', string

src/sim/host.hh

@@ -56,7 +56,7 @@ typedef int64_t Counter;
  */
 typedef int64_t Tick;
 
-const Tick MaxTick = (1LL << 62);
+const Tick MaxTick = (1LL << 63) - 1;
 
 /**
  * Address type

src/sim/main.cc

@@ -309,18 +309,14 @@ finalInit()
  * @return The SimLoopExitEvent that caused the loop to exit.
  */
 SimLoopExitEvent *
-simulate(Tick num_cycles = -1)
+simulate(Tick num_cycles = MaxTick)
 {
     warn("Entering event queue @ %d.  Starting simulation...\n", curTick);
 
-    // Fix up num_cycles.  Special default value -1 means simulate
-    // "forever"... schedule event at MaxTick just to be safe.
-    // Otherwise it's a delta for additional cycles to simulate past
-    // curTick, and thus must be non-negative.
-    if (num_cycles == -1)
-        num_cycles = MaxTick;
-    else if (num_cycles < 0)
+    if (num_cycles < 0)
         fatal("simulate: num_cycles must be >= 0 (was %d)\n", num_cycles);
+    else if (curTick + num_cycles < 0)  //Overflow
+        num_cycles = MaxTick;
     else
         num_cycles = curTick + num_cycles;