Convert diamond shaped control flow into a single conditional instruction.

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 561072f0d549a37bcd03fffd786765f8c988e2a2..320e5132a36b164167a61f562ffab5250ab257e8 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -106,6 +106,30 @@ void ReturnInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
+bool IfThenElseInstr::IsSupported() {
+  return false;
+}
+
+
+bool IfThenElseInstr::Supports(ComparisonInstr* comparison,
+                               Value* v1,
+                               Value* v2) {
+  UNREACHABLE();
+  return false;
+}
+
+
+LocationSummary* IfThenElseInstr::MakeLocationSummary() const {
+  UNREACHABLE();
+  return NULL;
+}
+
+
+void IfThenElseInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  UNREACHABLE();
+}
+
+
 LocationSummary* ClosureCallInstr::MakeLocationSummary() const {
   UNIMPLEMENTED();
   return NULL;