Stack allocate lexical locals + hoist stack slots

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 4248 matching lines @@
 
   // Return the name of the given parameter.
   String* ParameterName(int var);
 
   // Return the name of the given local.
   String* LocalName(int var);
 
   // Return the name of the given stack local.
   String* StackLocalName(int var);
 
+  // Return the name of the given stack local.
+  int StackLocalIndex(int var);
+
   // Return the name of the given context local.
   String* ContextLocalName(int var);
 
   // Return the mode of the given context local.
   VariableMode ContextLocalMode(int var);
 
   // Return the initialization flag of the given context local.
   InitializationFlag ContextLocalInitFlag(int var);
 
   // Return the initialization flag of the given context local.
@@ skipping 88 matching lines @@
 #undef FOR_EACH_NUMERIC_FIELD
     kVariablePartIndex
   };
 
   // The layout of the variable part of a ScopeInfo is as follows:
   // 1. ParameterEntries:
   //    This part stores the names of the parameters for function scopes. One
   //    slot is used per parameter, so in total this part occupies
   //    ParameterCount() slots in the array. For other scopes than function
   //    scopes ParameterCount() is 0.
+  // 2a.StackLocalFirstSlot:

[rossberg, 2015/04/21 14:41:02]

Nit: care to renumber?

[Dmitry Lomov (no reviews), 2015/04/21 16:59:24]

Done.

+  //    Index of a first stack slot for stack local.

[rossberg, 2015/04/21 14:41:01]

Can you please expand on this comment? It is rather central for understanding
the stack/scope layout, and this doesn't do it justice.

[Dmitry Lomov (no reviews), 2015/04/21 16:59:24]

Done.

   // 2. StackLocalEntries:
   //    Contains the names of local variables that are allocated on the stack,
   //    in increasing order of the stack slot index. One slot is used per stack
   //    local, so in total this part occupies StackLocalCount() slots in the
   //    array.
   // 3. ContextLocalNameEntries:
   //    Contains the names of local variables and parameters that are allocated
   //    in the context. They are stored in increasing order of the context slot
   //    index starting with Context::MIN_CONTEXT_SLOTS. One slot is used per
   //    context local, so in total this part occupies ContextLocalCount() slots
   //    in the array.
   // 4. ContextLocalInfoEntries:
   //    Contains the variable modes and initialization flags corresponding to
   //    the context locals in ContextLocalNameEntries. One slot is used per
   //    context local, so in total this part occupies ContextLocalCount()
   //    slots in the array.
   // 5. StrongModeFreeVariableNameEntries:
   //    Stores the names of strong mode free variables.
   // 6. StrongModeFreeVariablePositionEntries:
   //    Stores the locations (start and end position) of strong mode free
   //    variables.
   // 7. FunctionNameEntryIndex:
   //    If the scope belongs to a named function expression this part contains
   //    information about the function variable. It always occupies two array
   //    slots:  a. The name of the function variable.
   //            b. The context or stack slot index for the variable.
   int ParameterEntriesIndex();
+  int StackLocalFirstSlotIndex();
   int StackLocalEntriesIndex();
   int ContextLocalNameEntriesIndex();
   int ContextLocalInfoEntriesIndex();
   int StrongModeFreeVariableNameEntriesIndex();
   int StrongModeFreeVariablePositionEntriesIndex();
   int FunctionNameEntryIndex();
 
   // Location of the function variable for named function expressions.
   enum FunctionVariableInfo {
     NONE,     // No function name present.
@@ skipping 6677 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_