Specialize breakpoint stubs by set of live registers of the stubs they are intercepting.

runtime/vm/flow_graph_compiler_mips.cc

Index: runtime/vm/flow_graph_compiler_mips.cc
diff --git a/runtime/vm/flow_graph_compiler_mips.cc b/runtime/vm/flow_graph_compiler_mips.cc
index d86d7441fd180b2b06e4dd8c017958baa9bfd59b..e104e6d4658981d941310337689cc40ad44524a3 100644
--- a/runtime/vm/flow_graph_compiler_mips.cc
+++ b/runtime/vm/flow_graph_compiler_mips.cc
@@ -1248,7 +1248,6 @@ void FlowGraphCompiler::EmitInstanceCall(ExternalLabel* target_label,
                                          LocationSummary* locs) {
   ASSERT(Array::Handle(ic_data.arguments_descriptor()).Length() > 0);
   __ TraceSimMsg("InstanceCall");
-  __ LoadImmediate(S4, 0);
   __ LoadObject(S5, ic_data);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1341,7 +1340,6 @@ void FlowGraphCompiler::EmitUnoptimizedStaticCall(
     UNIMPLEMENTED();
   }
   ExternalLabel target_label(label_address);
-  __ LoadImmediate(S4, 0);
   __ LoadObject(S5, ic_data);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1422,8 +1420,6 @@ void FlowGraphCompiler::EmitEqualityRegRegCompare(Register left,
       __ BranchLinkPatchable(
           &StubCode::OptimizedIdenticalWithNumberCheckLabel());
     } else {
-      __ LoadImmediate(S4, 0);
-      __ LoadImmediate(S5, 0);
       __ BranchLinkPatchable(
           &StubCode::UnoptimizedIdenticalWithNumberCheckLabel());
     }