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

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
diff --git a/runtime/vm/flow_graph_compiler_x64.cc b/runtime/vm/flow_graph_compiler_x64.cc
index f183de655fb89816ec7438f46f46aaed4c9ef56a..df16564952daa127daf99f186fa5d9b7769d15e6 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -1219,7 +1219,6 @@ void FlowGraphCompiler::EmitUnoptimizedStaticCall(
     UNIMPLEMENTED();
   }
   ExternalLabel target_label(label_address);
-  __ movq(R10, Immediate(0));
   __ LoadObject(RBX, ic_data, PP);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1280,7 +1279,6 @@ void FlowGraphCompiler::EmitInstanceCall(ExternalLabel* target_label,
                                          intptr_t token_pos,
                                          LocationSummary* locs) {
   ASSERT(Array::Handle(ic_data.arguments_descriptor()).Length() > 0);
-  __ movq(R10, Immediate(0));
   __ LoadObject(RBX, ic_data, PP);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1419,8 +1417,6 @@ void FlowGraphCompiler::EmitEqualityRegRegCompare(Register left,
     if (is_optimizing()) {
       __ CallPatchable(&StubCode::OptimizedIdenticalWithNumberCheckLabel());
     } else {
-      __ movq(R10, Immediate(0));
-      __ movq(RBX, Immediate(0));
       __ CallPatchable(&StubCode::UnoptimizedIdenticalWithNumberCheckLabel());
     }
     if (token_pos != Scanner::kNoSourcePos) {