Add DoubleToSmi optimistically, preventing boxing/unboxing of doubles and propagate smi-nessof the …

runtime/vm/intrinsifier_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/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1374 matching lines @@
 }
 
 
 bool Intrinsifier::Double_toInt(Assembler* assembler) {
   __ movq(RAX, Address(RSP, +1 * kWordSize));
   __ movsd(XMM0, FieldAddress(RAX, Double::value_offset()));
   __ cvttsd2siq(RAX, XMM0);
   // Overflow is signalled with minint.
   Label fall_through;
   // Check for overflow and that it fits into Smi.
-  __ cmpq(RAX, Immediate(0xC000000000000000));
-  __ j(NEGATIVE, &fall_through, Assembler::kNearJump);
+  __ movq(RCX, RAX);
+  __ shlq(RCX, Immediate(1));
+  __ j(OVERFLOW, &fall_through, Assembler::kNearJump);
   __ SmiTag(RAX);
   __ ret();
   __ Bind(&fall_through);
   return false;
 }
 
 
 bool Intrinsifier::Math_sqrt(Assembler* assembler) {
   Label fall_through, is_smi, double_op;
   TestLastArgumentIsDouble(assembler, &is_smi, &fall_through);
@@ skipping 200 matching lines @@
   __ LoadObject(RAX, bool_true);
   __ ret();
   return true;
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64