Split array loads/stores for growable arrays into two IL instructions.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 12196)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -967,10 +967,12 @@
   // Returns true if the propagated cid has changed.
   bool SetPropagatedCid(intptr_t cid);
 
-  // Returns true if the definition may have side effects.
+  // Returns true if the definition is affected by side effects.
+  // Only instructions that are not affected by side effects can participate
+  // in redundancy elimination or loop invariant code motion.
   // TODO(fschneider): Make this abstract and implement for all definitions
   // instead of returning the safe default (true).
-  virtual bool HasSideEffect() const { return true; }
+  virtual bool AffectedBySideEffect() const { return true; }
 
   Value* input_use_list() { return input_use_list_; }
   void set_input_use_list(Value* head) { input_use_list_ = head; }
@@ -2228,6 +2230,9 @@
  public:
   LoadIndexedInstr(Value* array, Value* index, intptr_t receiver_type)
       : receiver_type_(receiver_type) {
+    ASSERT(receiver_type == kArrayCid ||
+           receiver_type == kImmutableArrayCid ||
+           receiver_type == kGrowableObjectArrayCid);
     ASSERT(array != NULL);
     ASSERT(index != NULL);
     inputs_[0] = array;
@@ -2259,6 +2264,9 @@
                     Value* value,
                     intptr_t receiver_type)
         : receiver_type_(receiver_type) {
+    ASSERT(receiver_type == kArrayCid ||
+           receiver_type == kImmutableArrayCid ||
+           receiver_type == kGrowableObjectArrayCid);
     ASSERT(array != NULL);
     ASSERT(index != NULL);
     ASSERT(value != NULL);
@@ -2498,10 +2506,12 @@
  public:
   LoadVMFieldInstr(Value* value,
                    intptr_t offset_in_bytes,
-                   const AbstractType& type)
+                   const AbstractType& type,
+                   bool immutable = false)

[srdjan, 2012/09/12 07:06:40]

I think setting immutable_ via a setter (similar to set_result_cid) is better:
no default arguments needed and better documentation at call site than passing
true/false. Otherwise, please make immutable_const.

[Florian Schneider, 2012/09/12 08:27:29]

Done. Making it const for now.

       : offset_in_bytes_(offset_in_bytes),
         type_(type),
-        result_cid_(kDynamicCid) {
+        result_cid_(kDynamicCid),
+        immutable_(immutable) {
     ASSERT(value != NULL);
     ASSERT(type.IsZoneHandle());  // May be null if field is not an instance.
     inputs_[0] = value;
@@ -2520,10 +2530,15 @@
   virtual bool CanDeoptimize() const { return false; }
   virtual intptr_t ResultCid() const { return result_cid_; }
 
+  bool AttributesEqual(Definition* other) const;
+
+  virtual bool AffectedBySideEffect() const { return !immutable_; }
+
  private:
   const intptr_t offset_in_bytes_;
   const AbstractType& type_;
   intptr_t result_cid_;
+  bool immutable_;
 
   DISALLOW_COPY_AND_ASSIGN(LoadVMFieldInstr);
 };
@@ -2776,7 +2791,7 @@
 
   virtual bool AttributesEqual(Definition* other) const { return true; }
 
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
 
   Value* left() const { return inputs_[0]; }
 
@@ -2802,7 +2817,7 @@
   intptr_t token_pos() const { return token_pos_; }
 
   virtual bool CanDeoptimize() const { return false; }
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
   virtual bool AttributesEqual(Definition* other) const { return true; }
 
   virtual intptr_t ResultCid() const;
@@ -2843,7 +2858,7 @@
     return kUnboxedDouble;
   }
 
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
   virtual bool AttributesEqual(Definition* other) const { return true; }
 
   DECLARE_INSTRUCTION(UnboxDouble)
@@ -2876,7 +2891,7 @@
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
   virtual bool CanDeoptimize() const { return false; }
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
 
   virtual bool AttributesEqual(Definition* other) const {
     return op_kind() == other->AsUnboxedDoubleBinaryOp()->op_kind();
@@ -3136,7 +3151,7 @@
 
   virtual bool AttributesEqual(Definition* other) const;
 
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
 
   Value* value() const { return inputs_[0]; }
 
@@ -3170,7 +3185,7 @@
 
   virtual bool AttributesEqual(Definition* other) const { return true; }
 
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
 
   virtual Definition* Canonicalize();
 
@@ -3203,7 +3218,7 @@
 
   virtual bool AttributesEqual(Definition* other) const;
 
-  virtual bool HasSideEffect() const { return false; }
+  virtual bool AffectedBySideEffect() const { return false; }
 
   Value* array() const { return inputs_[0]; }
   Value* index() const { return inputs_[1]; }