diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 989a748933..167334f39a 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -1084,18 +1084,19 @@ void Assembler::movq(Register dst, int64_t value, RelocInfo::Mode rmode) {
     // Sadly, there is no zero or sign extending move for 8-bit immediates.
     if (is_int32(value)) {
       movq(dst, Immediate(static_cast<int32_t>(value)));
+      return;
     } else if (is_uint32(value)) {
       movl(dst, Immediate(static_cast<int32_t>(value)));
+      return;
     }
     // Value cannot be represented by 32 bits, so do a full 64 bit immediate
     // value.
-  } else {
-    EnsureSpace ensure_space(this);
-    last_pc_ = pc_;
-    emit_rex_64(dst);
-    emit(0xB8 | dst.low_bits());
-    emitq(value, rmode);
   }
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  emit_rex_64(dst);
+  emit(0xB8 | dst.low_bits());
+  emitq(value, rmode);
 }
 
 
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index b4568237ae..b1f2b8fbce 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -5644,7 +5644,7 @@ void CompareStub::Generate(MacroAssembler* masm) {
       // The representation of NaN values has all exponent bits (52..62) set,
       // and not all mantissa bits (0..51) clear.
       // Read double representation into rax.
-      __ movq(rbx, 0x7ff0000000000000, RelocInfo::NONE);
+      __ movq(rbx, V8_UINT64_C(0x7ff0000000000000), RelocInfo::NONE);
       __ movq(rax, FieldOperand(rdx, HeapNumber::kValueOffset));
       // Test that exponent bits are all set.
       __ or_(rbx, rax);
@@ -5655,10 +5655,7 @@ void CompareStub::Generate(MacroAssembler* masm) {
       // If all bits in the mantissa are zero the number is Infinity, and
       // we return zero.  Otherwise it is a NaN, and we return non-zero.
       // We cannot just return rax because only eax is tested on return.
-      // TODO(X64): Solve this using movcc, when implemented.
-      __ movq(kScratchRegister, rax);
-      __ shr(kScratchRegister, Immediate(32));
-      __ or_(rax, kScratchRegister);
+      __ setcc(not_zero, rax);
       __ ret(0);
 
       __ bind(&not_identical);