Fix issue 974.

src/full-codegen.cc

Index: src/full-codegen.cc
diff --git a/src/full-codegen.cc b/src/full-codegen.cc
index 4eb10c7431dfd3e29045296a5f4517e6bcf2d119..7509628eb5d0be7b273d25cb8442027df42ea2c2 100644
--- a/src/full-codegen.cc
+++ b/src/full-codegen.cc
@@ -946,6 +946,11 @@ void FullCodeGenerator::VisitContinueStatement(ContinueStatement* stmt) {
   SetStatementPosition(stmt);
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  // When continuing, we clobber the unpredictable value in the accumulator
+  // with one that's safe for GC.  If we hit an exit from the try block of
+  // try...finally on our way out, we will unconditionally preserve the
+  // accumulator on the stack.
+  ClearAccumulator();
   while (!current->IsContinueTarget(stmt->target())) {
     stack_depth = current->Exit(stack_depth);
     current = current->outer();
@@ -962,6 +967,11 @@ void FullCodeGenerator::VisitBreakStatement(BreakStatement* stmt) {
   SetStatementPosition(stmt);
   NestedStatement* current = nesting_stack_;
   int stack_depth = 0;
+  // When breaking, we clobber the unpredictable value in the accumulator
+  // with one that's safe for GC.  If we hit an exit from the try block of
+  // try...finally on our way out, we will unconditionally preserve the
+  // accumulator on the stack.
+  ClearAccumulator();
   while (!current->IsBreakTarget(stmt->target())) {
     stack_depth = current->Exit(stack_depth);
     current = current->outer();
@@ -1235,7 +1245,10 @@ void FullCodeGenerator::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
     Visit(stmt->try_block());
     __ PopTryHandler();
   }
-  // Execute the finally block on the way out.
+  // Execute the finally block on the way out.  Clobber the unpredictable
+  // value in the accumulator with one that's safe for GC.  The finally
+  // block will unconditionally preserve the accumulator on the stack.
+  ClearAccumulator();
   __ Call(&finally_entry);
 }