VM: Improve and fix double negation on MIPS.

runtime/vm/intermediate_language_mips.cc

Index: runtime/vm/intermediate_language_mips.cc
diff --git a/runtime/vm/intermediate_language_mips.cc b/runtime/vm/intermediate_language_mips.cc
index 564245c75933cd51d091ead709543bb5dc1f6747..04713cd2f0f51a5329b3791f3277075e7473927d 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -4118,25 +4118,19 @@ void UnarySmiOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 LocationSummary* UnaryDoubleOpInstr::MakeLocationSummary(Zone* zone,
                                                          bool opt) const {
   const intptr_t kNumInputs = 1;
-  const intptr_t kNumTemps = 1;
+  const intptr_t kNumTemps = 0;
   LocationSummary* summary = new(zone) LocationSummary(
       zone, kNumInputs, kNumTemps, LocationSummary::kNoCall);
   summary->set_in(0, Location::RequiresFpuRegister());
   summary->set_out(0, Location::RequiresFpuRegister());
-  summary->set_temp(0, Location::RequiresFpuRegister());
   return summary;
 }
 
 
 void UnaryDoubleOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // TODO(zra): Implement vneg.
-  const Double& minus_one = Double::ZoneHandle(Double::NewCanonical(-1));
-  __ LoadObject(TMP, minus_one);
   FpuRegister result = locs()->out(0).fpu_reg();
   FpuRegister value = locs()->in(0).fpu_reg();
-  FpuRegister temp_fp = locs()->temp(0).fpu_reg();
-  __ LoadDFromOffset(temp_fp, TMP, Double::value_offset() - kHeapObjectTag);
-  __ muld(result, value, temp_fp);
+  __ negd(result, value);
 }