Turn CopyTemp and SetTemp into instructions.

runtime/vm/intermediate_language.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_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
 #include "vm/handles_impl.h"
 #include "vm/object.h"
 
 namespace dart {
 
 class FlowGraphVisitor;
 class LocalVariable;
 
 // Computations and values.
 //
 // <Computation> ::=
 //   <Value>
-// | CopyTemp <int>
-// | SetTemp <int>
 // | AssertAssignable <Value> <AbstractType>
 // | InstanceCall <AstNode> <String> <Value> ...
 // | StaticCall <StaticCallNode> <Value> ...
 // | LoadLocal <LocalVariable>
 // | StoreLocal <LocalVariable> <Value>
 // | StrictCompare <Token::kind> <Value> <Value>
 // | NativeCall <NativeBodyNode>
 // | StoreIndexed <StoreIndexedNode> <Value> <Value> <Value>
 // | InstanceSetter <InstanceSetterNode> <Value> <Value>
 // | LoadInstanceField <LoadInstanceFieldNode> <Value>
 // | StoreInstanceField <StoreInstanceFieldNode> <Value> <Value>
 // | LoadStaticField <Field>
 // | StoreStaticField <StoreStaticFieldNode> <Value>
 //
 // <Value> ::=
 //   Temp <int>
 // | Constant <Instance>
 
 // M is a two argument macro.  It is applied to each concrete value's
 // typename and classname.
 #define FOR_EACH_VALUE(M)                                                      \
   M(Temp, TempVal)                                                             \
   M(Constant, ConstantVal)                                                     \
 
 
 // M is a two argument macro.  It is applied to each concrete instruction's
 // (including the values) typename and classname.
 #define FOR_EACH_COMPUTATION(M)                                                \
   FOR_EACH_VALUE(M)                                                            \
-  M(CopyTemp, CopyTempComp)                                                    \
-  M(SetTemp, SetTempComp)                                                      \
   M(AssertAssignable, AssertAssignableComp)                                    \
   M(InstanceCall, InstanceCallComp)                                            \
   M(StaticCall, StaticCallComp)                                                \
   M(LoadLocal, LoadLocalComp)                                                  \
   M(StoreLocal, StoreLocalComp)                                                \
   M(StrictCompare, StrictCompareComp)                                          \
   M(NativeCall, NativeCallComp)                                                \
   M(StoreIndexed, StoreIndexedComp)                                            \
   M(InstanceSetter, InstanceSetterComp)                                        \
   M(LoadInstanceField, LoadInstanceFieldComp)                                  \
@@ skipping 71 matching lines @@
 
  private:
   const Instance& instance_;
 
   DISALLOW_COPY_AND_ASSIGN(ConstantVal);
 };
 
 #undef DECLARE_VALUE
 
 
-// A computation that produces a copy of a (random-access) temporary.  The
-// index is relative to the last temporary allocated (e.g., the last
-// temporary is index 0, the one before that is -1, etc.).  This instruction
-// is used in the non-optimizing backend and compiled away in the optimizing
-// backend.
-class CopyTempComp : public Computation {
- public:
-  explicit CopyTempComp(intptr_t index) : index_(index) { }
-
-  DECLARE_COMPUTATION(CopyTemp)
-
-  intptr_t index() const { return index_; }
-
- private:
-  const intptr_t index_;
-
-  DISALLOW_COPY_AND_ASSIGN(CopyTempComp);
-};
-
-
-// A computation that assigns (a duplicate of) the last allocated temporary
-// to a random-access already allocated temporary.  The index is relative to
-// the last temporary allocated (e.g., the last temporary is index 0, the
-// one before that is -1, etc.).  This instruction is used in the
-// non-optimizing backend and compiled away in the optimizing backend.
-class SetTempComp : public Computation {
- public:
-  explicit SetTempComp(intptr_t index) : index_(index) { }
-
-  DECLARE_COMPUTATION(SetTemp)
-
-  intptr_t index() const { return index_; }
-
- private:
-  const intptr_t index_;
-
-  DISALLOW_COPY_AND_ASSIGN(SetTempComp);
-};
-
-
 class AssertAssignableComp : public Computation {
  public:
   AssertAssignableComp(Value* value, const AbstractType& type)
       : value_(value), type_(type) { }
 
   DECLARE_COMPUTATION(AssertAssignable)
 
   Value* value() const { return value_; }
   const AbstractType& type() const { return type_; }
 
@@ skipping 288 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(InstanceSetterComp);
 };
 
 
 #undef DECLARE_COMPUTATION
 
 
 // Instructions.
 //
-// <Instruction> ::= Do <Computation> <Instruction>
+// <Instruction> ::= JoinEntry <Instruction>
+//                 | TargetEntry <Instruction>
+//                 | PickTemp <int> <int> <Instruction>
+//                 | TuckTemp <int> <int> <Instruction>
+//                 | Do <Computation> <Instruction>
 //                 | Bind <int> <Computation> <Instruction>
 //                 | Return <Value>
 //                 | Branch <Value> <Instruction> <Instruction>
-//                 | Empty <Instruction>
 
 // M is a single argument macro.  It is applied to each concrete instruction
 // type name.  The concrete instruction classes are the name with Instr
 // concatenated.
 #define FOR_EACH_INSTRUCTION(M)                                                \
   M(JoinEntry)                                                                 \
   M(TargetEntry)                                                               \
+  M(PickTemp)                                                                  \
+  M(TuckTemp)                                                                  \
   M(Do)                                                                        \
   M(Bind)                                                                      \
   M(Return)                                                                    \
-  M(Branch)
+  M(Branch)                                                                    \
 
 
 // Forward declarations for Instruction classes.
 class BlockEntryInstr;
 #define FORWARD_DECLARATION(type) class type##Instr;
 FOR_EACH_INSTRUCTION(FORWARD_DECLARATION)
 #undef FORWARD_DECLARATION
 
 
 // Functions required in all concrete instruction classes.
@@ skipping 97 matching lines @@
 
   virtual void Postorder(GrowableArray<BlockEntryInstr*>* block_entries);
 
  private:
   Instruction* successor_;
 
   DISALLOW_COPY_AND_ASSIGN(TargetEntryInstr);
 };
 
 
+// The non-optimizing compiler assumes that there is exactly one use of
+// every temporary so they can be deallocated at their use.  Some AST nodes,
+// e.g., expr0[expr1]++, violate this assumption (there are two uses of each
+// of the values expr0 and expr1).
+//
+// PickTemp is used to name (with 'destination') a copy of a live temporary
+// (named 'source') without counting as the use of the source.
+class PickTempInstr : public Instruction {
+ public:
+  PickTempInstr(intptr_t dst, intptr_t src)
+      : Instruction(), destination_(dst), source_(src), successor_(NULL) { }
+
+  DECLARE_INSTRUCTION(PickTemp)
+
+  intptr_t destination() const { return destination_; }
+  intptr_t source() const { return source_; }
+
+  virtual void SetSuccessor(Instruction* instr) {
+    ASSERT(successor_ == NULL && instr != NULL);
+    successor_ = instr;
+  }
+
+  virtual void Postorder(GrowableArray<BlockEntryInstr*>* block_entries);
+
+ private:
+  const intptr_t destination_;
+  const intptr_t source_;
+  Instruction* successor_;
+
+  DISALLOW_COPY_AND_ASSIGN(PickTempInstr);
+};
+
+
+// The non-optimizing compiler assumes that temporary definitions and uses
+// obey a stack discipline, so they can be allocated and deallocated with
+// push and pop.  Some Some AST nodes, e.g., expr++, violate this assumption
+// (the value expr+1 is produced after the value of expr, and also consumed
+// after it).
+//
+// We 'preallocate' temporaries (named with 'destination') such as the one
+// for expr+1 and use TuckTemp to mutate them by overwriting them with a
+// copy of a temporary (named with 'source').
+class TuckTempInstr : public Instruction {
+ public:
+  TuckTempInstr(intptr_t dst, intptr_t src)
+      : Instruction(), destination_(dst), source_(src), successor_(NULL) { }
+
+  DECLARE_INSTRUCTION(TuckTemp)
+
+  intptr_t destination() const { return destination_; }
+  intptr_t source() const { return source_; }
+
+  virtual void SetSuccessor(Instruction* instr) {
+    ASSERT(successor_ == NULL && instr != NULL);
+    successor_ = instr;
+  }
+
+  virtual void Postorder(GrowableArray<BlockEntryInstr*>* block_entries);
+
+ private:
+  const intptr_t destination_;
+  const intptr_t source_;
+  Instruction* successor_;
+
+  DISALLOW_COPY_AND_ASSIGN(TuckTempInstr);
+};
+
+
 class DoInstr : public Instruction {
  public:
   explicit DoInstr(Computation* comp)
       : Instruction(), computation_(comp), successor_(NULL) { }
 
   DECLARE_INSTRUCTION(Do)
 
   Computation* computation() const { return computation_; }
 
   virtual void SetSuccessor(Instruction* instr) {
@@ skipping 120 matching lines @@
 #undef DECLARE_VISIT_INSTRUCTION
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_