Fix -O0 compilation errors

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 612d97e4f4b42406adc129511a5e72db629045ad..f583fa1e13b2ab3c4a0bf2aa4a2b55abedded3e0 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -1772,13 +1772,11 @@ LocationSummary* GuardFieldLengthInstr::MakeLocationSummary(Zone* zone,
     // We need temporaries for field object.
     summary->set_temp(0, Location::RequiresRegister());
     return summary;
-  } else {
-    LocationSummary* summary = new(zone) LocationSummary(
-        zone, kNumInputs, 0, LocationSummary::kNoCall);
-    summary->set_in(0, Location::RequiresRegister());
-    return summary;
   }
-  UNREACHABLE();
+  LocationSummary* summary = new(zone) LocationSummary(
+      zone, kNumInputs, 0, LocationSummary::kNoCall);
+  summary->set_in(0, Location::RequiresRegister());
+  return summary;
 }