More general dead phi elimination.

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 2860 matching lines @@
   ASSERT(new_min.IsUnknown() == new_max.IsUnknown());
   if (new_min.IsUnknown()) {
     range_ = Range::Unknown();
     return;
   }
 
   range_ = new Range(new_min, new_max);
 }
 
 
+bool PhiInstr::IsRedundant() const {
+  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;
+}
+
+
 static bool SymbolicSub(const RangeBoundary& a,
                         const RangeBoundary& b,
                         RangeBoundary* result) {
   if (a.IsSymbol() && b.IsConstant() && !b.Overflowed()) {
     const intptr_t offset = a.offset() - b.value();
     if (!Smi::IsValid(offset)) return false;
 
     *result = RangeBoundary::FromDefinition(a.symbol(), offset);
     return true;
   }
@@ skipping 510 matching lines @@
     case Token::kTRUNCDIV: return 0;
     case Token::kMOD: return 1;
     default: UNIMPLEMENTED(); return -1;
   }
 }
 
 
 #undef __
 
 }  // namespace dart