Constant fold strict comparison based on incoming types: different (exact) types means that the res…

runtime/vm/flow_graph_optimizer.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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 6295 matching lines @@
     SetValue(instr, Bool::Get(instr->kind() == Token::kEQ_STRICT));
     return;
   }
 
   if (IsNonConstant(left) || IsNonConstant(right)) {
     // TODO(vegorov): incorporate nullability information into the lattice.
     if ((left.IsNull() && instr->right()->Type()->HasDecidableNullability()) ||
         (right.IsNull() && instr->left()->Type()->HasDecidableNullability())) {
       bool result = left.IsNull() ? instr->right()->Type()->IsNull()
                                   : instr->left()->Type()->IsNull();
-      if (instr->kind() == Token::kNE_STRICT) result = !result;
+      if (instr->kind() == Token::kNE_STRICT) {
+        result = !result;
+      }
       SetValue(instr, Bool::Get(result));
     } else {
-      SetValue(instr, non_constant_);
+      const intptr_t left_cid = instr->left()->Type()->ToCid();
+      const intptr_t right_cid = instr->right()->Type()->ToCid();
+      // If exact classes (cids) are known and they differ, the result
+      // of strict compare can be computed.
+      if ((left_cid != kDynamicCid) && (right_cid != kDynamicCid) &&
+          (left_cid != right_cid)) {
+        const bool result = (instr->kind() != Token::kEQ_STRICT);
+        SetValue(instr, Bool::Get(result));
+      } else {
+        SetValue(instr, non_constant_);
+      }
     }
   } else if (IsConstant(left) && IsConstant(right)) {
     bool result = (left.raw() == right.raw());
-    if (instr->kind() == Token::kNE_STRICT) result = !result;
+    if (instr->kind() == Token::kNE_STRICT) {
+      result = !result;
+    }
     SetValue(instr, Bool::Get(result));
   }
 }
 
 
 static bool CompareIntegers(Token::Kind kind,
                             const Integer& left,
                             const Integer& right) {
   const int result = left.CompareWith(right);
   switch (kind) {
@@ skipping 1558 matching lines @@
   }
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, alloc->cls(), *fields);
   }
 }
 
 
 }  // namespace dart