Split Thread/Isolate instances, but still maintain 1:1 relationship.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
===================================================================
--- runtime/vm/compiler.cc	(revision 44671)
+++ runtime/vm/compiler.cc	(working copy)
@@ -178,7 +178,7 @@
 
 
 RawError* Compiler::Compile(const Library& library, const Script& script) {
-  Isolate* isolate = Isolate::Current();
+  Isolate* volatile isolate = Isolate::Current();

[siva, 2015/03/25 21:26:34]

What is the rationale for adding the 'volatile' keyword?

[koda, 2015/03/25 21:49:47]

Without it, some compilers issue a warning about this local possibly being
clobbered between the setjmp/longjmp. However, I believe this warning is
unfounded, since the spec says this only happens if the local is actually
modified between the setjmp and longjmp, which is not the case here.

We already have a similar issue in flow_graph_inliner.cc:
https://github.com/dart-lang/bleeding_edge/blob/master/dart/runtime/vm/flow_g...

[Ivan Posva, 2015/03/26 14:36:52]

Please make this local a const, which it really is. That should remove the
warnings without the unclear meaning of volatile here.

   StackZone zone(isolate);
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
@@ -279,7 +279,7 @@
     }
   }
 
-  Isolate* isolate = Isolate::Current();
+  Isolate* volatile isolate = Isolate::Current();

[Ivan Posva, 2015/03/26 14:36:52]

ditto

   // We remember all the classes that are being compiled in these lists. This
   // also allows us to reset the marked_for_parsing state in case we see an
   // error.
@@ -376,7 +376,7 @@
   bool is_compiled = false;
   Thread* thread = Thread::Current();
   Zone* zone = thread->zone();
-  Isolate* isolate = thread->isolate();
+  Isolate* volatile isolate = thread->isolate();
   HANDLESCOPE(isolate);
 
   // We may reattempt compilation if the function needs to be assembled using
@@ -965,7 +965,7 @@
                                        bool optimized,
                                        intptr_t osr_id) {
   Thread* thread = Thread::Current();
-  Isolate* isolate = thread->isolate();
+  Isolate* volatile isolate = thread->isolate();
   StackZone stack_zone(isolate);
   Zone* zone = stack_zone.GetZone();
   LongJumpScope jump;
@@ -1065,7 +1065,7 @@
 // This is only used from unit tests.
 RawError* Compiler::CompileParsedFunction(
     ParsedFunction* parsed_function) {
-  Isolate* isolate = Isolate::Current();
+  Isolate* volatile isolate = Isolate::Current();
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
     // Non-optimized code generator.
@@ -1142,7 +1142,7 @@
   // The VM sets the field's value to transiton_sentinel prior to
   // evaluating the initializer value.
   ASSERT(field.value() == Object::transition_sentinel().raw());
-  Isolate* isolate = Isolate::Current();
+  Isolate* volatile isolate = Isolate::Current();
   StackZone zone(isolate);
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
@@ -1176,7 +1176,7 @@
 
 RawObject* Compiler::ExecuteOnce(SequenceNode* fragment) {
   Thread* thread = Thread::Current();
-  Isolate* isolate = thread->isolate();
+  Isolate* volatile isolate = thread->isolate();
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
     if (FLAG_trace_compiler) {