Move String interpolation constant folding from constant propagator to canonicalizer

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 29114)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -20,6 +20,8 @@
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
+#include "vm/il_printer.h"
+
 namespace dart {
 
 DEFINE_FLAG(int, max_equality_polymorphic_checks, 32,
@@ -2719,6 +2721,65 @@
 }
 
 
+// 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)
+  CreateArrayInstr* create_array = value()->definition()->AsCreateArray();
+  ASSERT(create_array != NULL);
+  // Check if the string interpolation has only constant inputs.
+  GrowableArray<ConstantInstr*> constants(create_array->num_elements());
+  for (intptr_t i = 0; i < create_array->num_elements(); i++) {
+    constants.Add(NULL);
+  }
+  for (Value::Iterator it(create_array->input_use_list());
+       !it.Done();
+       it.Advance()) {
+    Instruction* curr = it.Current()->instruction();
+    if (curr != this) {
+      StoreIndexedInstr* store = curr->AsStoreIndexed();
+      ASSERT(store != NULL);
+      if (store->value()->definition()->IsConstant()) {
+        ASSERT(store->index()->BindsToConstant());
+        const Object& obj = store->value()->definition()->AsConstant()->value();
+        if (obj.IsNumber() || obj.IsString() || obj.IsBool() || obj.IsNull()) {
+          constants[Smi::Cast(store->index()->BoundConstant()).Value()] =
+              store->value()->definition()->AsConstant();
+        } else {
+          return this;
+        }
+      } else {
+        return this;
+      }
+    }
+  }
+  // Interpolate string at compile time.
+  const Array& array_argument =
+      Array::Handle(Array::New(create_array->num_elements()));
+  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()) {
+    return this;
+  }
+  concatenated = Symbols::New(concatenated);
+  return flow_graph->GetConstant(concatenated);
+}
+
+
 InvokeMathCFunctionInstr::InvokeMathCFunctionInstr(
     ZoneGrowableArray<Value*>* inputs,
     intptr_t original_deopt_id,