Handle Symbols in the LBranch instruction on x64.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1978 matching lines @@
         // String value -> false iff empty.
         Label not_string;
         __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
         __ j(above_equal, &not_string, Label::kNear);
         __ cmpq(FieldOperand(reg, String::kLengthOffset), Immediate(0));
         __ j(not_zero, instr->TrueLabel(chunk_));
         __ jmp(instr->FalseLabel(chunk_));
         __ bind(&not_string);
       }
 
+      if (expected.Contains(ToBooleanStub::SYMBOL)) {
+        // Symbol value -> true.
+        __ CmpInstanceType(map, SYMBOL_TYPE);
+        __ j(equal, instr->TrueLabel(chunk_));
+      }
+
       if (expected.Contains(ToBooleanStub::HEAP_NUMBER)) {
         // heap number -> false iff +0, -0, or NaN.
         Label not_heap_number;
         __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
         __ j(not_equal, &not_heap_number, Label::kNear);
         __ xorps(xmm0, xmm0);
         __ ucomisd(xmm0, FieldOperand(reg, HeapNumber::kValueOffset));
         __ j(zero, instr->FalseLabel(chunk_));
         __ jmp(instr->TrueLabel(chunk_));
         __ bind(&not_heap_number);
@@ skipping 3582 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64