Add a fixed array type.

lib/compiler/implementation/ssa/nodes.dart

 // 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.
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ skipping 815 matching lines @@
   bool useGvn() => getFlag(FLAG_USE_GVN);
   void setUseGvn() { setFlag(FLAG_USE_GVN); }
   // Does this node potentially affect control flow.
   bool isControlFlow() => false;
 
   // All isFunctions work on the propagated types.
   bool isArray(HTypeMap types) => types[this].isArray();
   bool isReadableArray(HTypeMap types) => types[this].isReadableArray();
   bool isMutableArray(HTypeMap types) => types[this].isMutableArray();
   bool isExtendableArray(HTypeMap types) => types[this].isExtendableArray();
+  bool isFixedArray(HTypeMap types) => types[this].isFixedArray();
   bool isBoolean(HTypeMap types) => types[this].isBoolean();
   bool isInteger(HTypeMap types) => types[this].isInteger();
   bool isDouble(HTypeMap types) => types[this].isDouble();
   bool isNumber(HTypeMap types) => types[this].isNumber();
   bool isString(HTypeMap types) => types[this].isString();
   bool isTypeUnknown(HTypeMap types) => types[this].isUnknown();
   bool isIndexablePrimitive(HTypeMap types)
       => types[this].isIndexablePrimitive();
   bool isPrimitive(HTypeMap types) => types[this].isPrimitive();
   bool canBePrimitive(HTypeMap types) => types[this].canBePrimitive();
@@ skipping 579 matching lines @@
         return HType.MUTABLE_ARRAY;
       }
     }
     return HType.UNKNOWN;
   }
 
   void prepareGvn(HTypeMap types) {
     if (isLengthGetterOnStringOrArray(types)) {
       setUseGvn();
       clearAllSideEffects();
-      // If the input is a string, we know the length cannot change.
-      // We cannot do the same thing for non-extendable array because
-      // we don't express that type yet: a mutable array might be
-      // extendable.
-      if (!inputs[1].isString(types)) setDependsOnSomething();
+      // If the input is a string or a fixed length array, we know
+      // the length cannot change.
+      if (!inputs[1].isString(types) && !inputs[1].isFixedArray(types)) {
+        setDependsOnSomething();
+      }
     } else if (isSideEffectFree) {
       setUseGvn();
       clearAllSideEffects();
       setDependsOnSomething();
     } else {
       setAllSideEffects();
     }
   }
 
   int typeCode() => HInstruction.INVOKE_INTERCEPTOR_TYPECODE;
@@ skipping 1467 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }