Have the flow graph builder collect definitions.

src/data-flow.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 413 matching lines @@
   graph_.AppendInstruction(expr);
 }
 
 
 void FlowGraphBuilder::VisitAssignment(Assignment* expr) {
   Variable* var = expr->target()->AsVariableProxy()->AsVariable();
   Property* prop = expr->target()->AsProperty();
   // Left-hand side can be a variable or property (or reference error) but
   // not both.
   ASSERT(var == NULL || prop == NULL);
-  if (prop != NULL) {
+  if (var != NULL) {
+    Visit(expr->value());
+    Slot* slot = var->slot();
+    if (slot != NULL &&

[fschneider, 2010/03/09 09:23:05]

I'm also checking for stack locals and parameters in many locations in the
assigned variables analysis. This would be a candidate for a helper function.

+        (slot->type() == Slot::LOCAL || slot->type() == Slot::PARAMETER)) {
+      definitions_.Add(expr);
+    }
+
+  } else if (prop != NULL) {
     Visit(prop->obj());
     if (!prop->key()->IsPropertyName()) Visit(prop->key());
-  }
-  if (var != NULL || prop != NULL) {
     Visit(expr->value());
   }
   graph_.AppendInstruction(expr);
 }
 
 
 void FlowGraphBuilder::VisitThrow(Throw* expr) {
   Visit(expr->exception());
   graph_.AppendInstruction(expr);
 }
@@ skipping 36 matching lines @@
 
 
 void FlowGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
   Visit(expr->expression());
   graph_.AppendInstruction(expr);
 }
 
 
 void FlowGraphBuilder::VisitCountOperation(CountOperation* expr) {
   Visit(expr->expression());
+  Variable* var = expr->expression()->AsVariableProxy()->AsVariable();

[fschneider, 2010/03/09 09:23:05]

Sometimes we use 

...->AsVariableProxy()->var()

and sometimes

...->AsVariableProxy()->AsVariable()

This is not part of this change, but could we get rid of one of them?

+  if (var != NULL) {
+    Slot* slot = var->slot();
+    if (slot != NULL &&
+        (slot->type() == Slot::LOCAL || slot->type() == Slot::PARAMETER)) {
+      definitions_.Add(expr);
+    }
+  }
   graph_.AppendInstruction(expr);
 }
 
 
 void FlowGraphBuilder::VisitBinaryOperation(BinaryOperation* expr) {
   Visit(expr->left());
 
   switch (expr->op()) {
     case Token::COMMA:
       Visit(expr->right());
@@ skipping 947 matching lines @@
   for (int i = postorder->length() - 1; i >= 0; i--) {
     postorder->at(i)->PrintText();
   }
 }
 
 
 #endif  // defined(DEBUG)
 
 
 } }  // namespace v8::internal