MIPS64: Fix move operations from coprocessor in simulator.

src/mips64/simulator-mips64.cc

Index: src/mips64/simulator-mips64.cc
diff --git a/src/mips64/simulator-mips64.cc b/src/mips64/simulator-mips64.cc
index 2feca96fbca13bdca185d4745f4a1d5c046198f6..4c74939d43ac71f6b4bcbccce2be786819aeb121 100644
--- a/src/mips64/simulator-mips64.cc
+++ b/src/mips64/simulator-mips64.cc
@@ -1109,9 +1109,9 @@ int32_t Simulator::get_fpu_register_signed_word(int fpureg) const {
 }
 
 
-uint32_t Simulator::get_fpu_register_hi_word(int fpureg) const {
+int32_t Simulator::get_fpu_register_hi_word(int fpureg) const {
   DCHECK((fpureg >= 0) && (fpureg < kNumFPURegisters));
-  return static_cast<uint32_t>((FPUregisters_[fpureg] >> 32) & 0xffffffff);
+  return static_cast<int32_t>((FPUregisters_[fpureg] >> 32) & 0xffffffff);
 }