Eliminate temporary locals for some expressions

runtime/vm/scopes.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_SCOPES_H_
 #define VM_SCOPES_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/growable_array.h"
@@ skipping 45 matching lines @@
   bool HasIndex() const {
     return index_ != kUnitializedIndex;
   }
   int index() const {
     ASSERT(HasIndex());
     return index_;
   }
 
   // Assign an index to a local.
   void set_index(int index) {
-    ASSERT(!HasIndex());

[hausner, 2013/05/28 17:00:47]

Why are you removing these asserts? Does your change depend on being able to set
an index on a variable that has already been allocated? That would seem wrong to
me.

[Florian Schneider, 2013/05/30 09:29:31]

I'm setting the index of the new dynamically allocated temps in the graph
builder where I track the stack height used for the index calculation. I could
make the graph builder a friend class of LocalVariable to keep the assert for
the existing uses of set_index.

Since the inliner uses a cache of ASTs we may encounter a local variable
multiple times when inlining at two call-sites that call the same function.

I agree this is a little brittle. I think a better solution would be to avoid
re-using the LocalVariable class for my purpose, but that would involve a lot of
changes, so I didn't want to do that in the first step.

The second ASSERT can actually stay. I removed it over-eagerly.

-    ASSERT(index != kUnitializedIndex);
     index_ = index;
   }
 
   void set_invisible(bool value) {
     is_invisible_ = value;
   }
 
   bool IsConst() const {
     return const_value_ != NULL;
   }
@@ skipping 283 matching lines @@
   intptr_t end_token_pos_;    // Token index of end of scope.
   GrowableArray<LocalVariable*> variables_;
   GrowableArray<SourceLabel*> labels_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCOPES_H_