Do not silently convert integers to doubles in binary operations. Only when at least one of argumen…

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2012, 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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 1749 matching lines @@
   __ popq(right);
   __ popq(left);
 
   Label* deopt = compiler->AddDeoptStub(instance_call()->deopt_id(),
                                         instance_call()->token_pos(),
                                         instance_call()->try_index(),
                                         kDeoptDoubleBinaryOp,
                                         left,
                                         right);
 
+  // Binary operation of two Smi's produces a Smi not a double.
+  __ movq(temp, left);
+  __ orq(temp, right);
+  __ testq(temp, Immediate(kSmiTagMask));
+  __ j(ZERO, deopt);
+
   compiler->LoadDoubleOrSmiToXmm(XMM0, left, temp, deopt);
   compiler->LoadDoubleOrSmiToXmm(XMM1, right, temp, deopt);
 
   switch (op_kind()) {
     case Token::kADD: __ addsd(XMM0, XMM1); break;
     case Token::kSUB: __ subsd(XMM0, XMM1); break;
     case Token::kMUL: __ mulsd(XMM0, XMM1); break;
     case Token::kDIV: __ divsd(XMM0, XMM1); break;
     default: UNREACHABLE();
   }
@@ skipping 323 matching lines @@
   ASSERT(locs()->out().reg() == RAX);
   __ CompareObject(locs()->out().reg(), compiler->bool_true());
   EmitBranchOnCondition(compiler, branch_condition);
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64