VM: Fix infinite recursion in optimization of of string interpolation.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, 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.
 
 #include "vm/intermediate_language.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/bit_vector.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 3025 matching lines @@
 // Replace StringInterpolateInstr with a constant string if all inputs are
 // constant of [string, number, boolean, null].
 // Leave the CreateArrayInstr and StoreIndexedInstr in the stream in case
 // deoptimization occurs.
 Definition* StringInterpolateInstr::Canonicalize(FlowGraph* flow_graph) {
   // The following graph structure is generated by the graph builder:
   //   v2 <- CreateArray(v0)
   //   StoreIndexed(v2, v3, v4)   -- v3:constant index, v4: value.
   //   ..
   //   v8 <- StringInterpolate(v2)
+
+  // Don't compile-time fold when optimizing the interpolation function itself.
+  if (flow_graph->parsed_function().function().raw() == CallFunction().raw()) {
+    return this;
+  }
+
   CreateArrayInstr* create_array = value()->definition()->AsCreateArray();
   ASSERT(create_array != NULL);
   // Check if the string interpolation has only constant inputs.
   Value* num_elements = create_array->num_elements();
   if (!num_elements->BindsToConstant() ||
       !num_elements->BoundConstant().IsSmi()) {
     return this;
   }
   intptr_t length = Smi::Cast(num_elements->BoundConstant()).Value();
   GrowableArray<ConstantInstr*> constants(length);
@@ skipping 24 matching lines @@
   // Interpolate string at compile time.
   const Array& array_argument =
       Array::Handle(Array::New(length));
   for (intptr_t i = 0; i < constants.length(); i++) {
     array_argument.SetAt(i, constants[i]->value());
   }
   // Build argument array to pass to the interpolation function.
   const Array& interpolate_arg = Array::Handle(Array::New(1));
   interpolate_arg.SetAt(0, array_argument);
   // Call interpolation function.
-  String& concatenated = String::ZoneHandle();
-  concatenated ^=
-      DartEntry::InvokeFunction(CallFunction(), interpolate_arg);
-  if (concatenated.IsUnhandledException()) {
+  const Object& result = Object::Handle(
+      DartEntry::InvokeFunction(CallFunction(), interpolate_arg));
+  if (result.IsUnhandledException()) {
     return this;
   }
-  concatenated = Symbols::New(concatenated);
+  ASSERT(result.IsString());
+  const String& concatenated =
+      String::ZoneHandle(Symbols::New(String::Cast(result)));
   return flow_graph->GetConstant(concatenated);
 }
 
 
 InvokeMathCFunctionInstr::InvokeMathCFunctionInstr(
     ZoneGrowableArray<Value*>* inputs,
     intptr_t original_deopt_id,
     MethodRecognizer::Kind recognized_kind)
     : inputs_(inputs),
       recognized_kind_(recognized_kind) {
@@ skipping 128 matching lines @@
     case Token::kTRUNCDIV: return 0;
     case Token::kMOD: return 1;
     default: UNIMPLEMENTED(); return -1;
   }
 }
 
 
 #undef __
 
 }  // namespace dart