Replace guarded list length field loads with constants

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index a3266fabf9dd230c416e4c4ccdd19f88a2326070..6e8bf299fbf974712a7dfe5d417744ed8c49bd85 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -6488,7 +6488,8 @@ class CheckSmiInstr : public TemplateInstruction<1> {
 
 class CheckArrayBoundInstr : public TemplateInstruction<2> {
  public:
-  CheckArrayBoundInstr(Value* length, Value* index, intptr_t deopt_id) {
+  CheckArrayBoundInstr(const Field* field, Value* length, Value* index,
+                       intptr_t deopt_id) : field_(field) {

[srdjan, 2013/08/27 15:50:33]

Why store field instead of guarded_list _length or kNoFixedLength?

     SetInputAt(kLengthPos, length);
     SetInputAt(kIndexPos, index);
     // Override generated deopt-id.
@@ -6508,6 +6509,11 @@ class CheckArrayBoundInstr : public TemplateInstruction<2> {
 
   virtual Instruction* Canonicalize(FlowGraph* flow_graph);
 
+  intptr_t GetGuardedArrayLength() const {
+    if (field_ == NULL) return Field::kNoFixedLength;

[Florian Schneider, 2013/08/27 12:51:34]

Style suggestion:

return (field_ == NULL) ? Field::kNoFixedLength : field_->guarded_list_length();

+    return field_->guarded_list_length();
+  }
+
   // Returns the length offset for array and string types.
   static intptr_t LengthOffsetFor(intptr_t class_id);
 
@@ -6526,6 +6532,7 @@ class CheckArrayBoundInstr : public TemplateInstruction<2> {
     kLengthPos = 0,
     kIndexPos = 1
   };
+  const Field* field_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckArrayBoundInstr);
 };