vm: separate 'current_gc_p' from 'current_gc'

The 'current_gc' handle doesn't need to be volatile, just the state of GC-ness

vm/gc.cpp

@@ -155,6 +155,7 @@ void factor_vm::gc(gc_op op, cell requested_size, bool trace_contexts_p)
 	assert(!data->high_fragmentation_p());
 
 	current_gc = new gc_state(op,this);
+	atomic::store(&current_gc_p, true);
 
 	/* Keep trying to GC higher and higher generations until we don't run
 	out of space in the target generation. */
@@ -217,6 +218,7 @@ void factor_vm::gc(gc_op op, cell requested_size, bool trace_contexts_p)
 
 	end_gc();
 
+	atomic::store(&current_gc_p, false);
 	delete current_gc;
 	current_gc = NULL;
 

vm/vm.cpp

@@ -12,6 +12,8 @@ factor_vm::factor_vm() :
 	safepoint_fep_p(false),
 	gc_off(false),
 	current_gc(NULL),
+	current_gc_p(false),
+	current_jit_p(false),
 	gc_events(NULL),
 	fep_p(false),
 	fep_help_was_shown(false),

vm/vm.hpp

@@ -91,7 +91,11 @@ struct factor_vm
 	callback_heap *callbacks;
 
 	/* Only set if we're performing a GC */
-	volatile gc_state *current_gc;
+	gc_state *current_gc;
+	volatile cell current_gc_p;
+
+	/* Set if we're in the jit */
+	volatile cell current_jit_p;
 
 	/* Mark stack */
 	std::vector<cell> mark_stack;