VM: Improve phi-elimination to improve code inside of try-catch.

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/bit_vector.h"
 #include "vm/bootstrap.h"
 #include "vm/compiler.h"
 #include "vm/constant_propagator.h"
@@ skipping 3502 matching lines @@
   ASSERT(InputCount() > 1);
   Definition* first = InputAt(0)->definition();
   for (intptr_t i = 1; i < InputCount(); ++i) {
     Definition* def = InputAt(i)->definition();
     if (def != first) return false;
   }
   return true;
 }
 
 
+bool PhiInstr::HasReplacement(Definition** replacement) const {
+  ASSERT(InputCount() > 1);
+  ASSERT(!IsRedundant());
+  // At least >=1 inputs are different from 'this': Check for
+  // v <- phi (v, v, ..., r, v, ..., v)
+  // where r is the replacement.
+  intptr_t i = 0;
+  while (InputAt(i)->definition() == this) ++i;
+  *replacement = InputAt(i)->definition();
+  while (++i < InputCount()) {
+    if (InputAt(i)->definition() != this) return false;
+  }
+  return true;
+}
+
+
 bool CheckArrayBoundInstr::IsFixedLengthArrayType(intptr_t cid) {
   return LoadFieldInstr::IsFixedLengthArrayCid(cid);
 }
 
 
 Instruction* CheckArrayBoundInstr::Canonicalize(FlowGraph* flow_graph) {
   return IsRedundant(RangeBoundary::FromDefinition(length()->definition())) ?
       NULL : this;
 }
 
@@ skipping 337 matching lines @@
   set_native_c_function(native_function);
   function().SetIsNativeAutoSetupScope(auto_setup_scope);
   Dart_NativeEntryResolver resolver = library.native_entry_resolver();
   bool is_bootstrap_native = Bootstrap::IsBootstapResolver(resolver);
   set_is_bootstrap_native(is_bootstrap_native);
 }
 
 #undef __
 
 }  // namespace dart