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 a601029d56149d572da3ce43ed343811f52299d8..36296e5e6fae4da4496305939b6b96e88af02b46 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -1225,7 +1225,6 @@ void FlowGraphCompiler::EmitUnoptimizedStaticCall(
     UNIMPLEMENTED();
   }
   ExternalLabel target_label(label_address);
-  __ movq(R10, Immediate(0));
   __ LoadObject(RBX, ic_data, PP);
   GenerateDartCall(deopt_id,
                    token_pos,
@@ -1234,6 +1233,7 @@ void FlowGraphCompiler::EmitUnoptimizedStaticCall(
                    locs);
   __ Drop(argument_count);
 #if defined(DEBUG)
+  __ movq(RBX, Immediate(kInvalidObjectPointer));
   __ movq(R10, Immediate(kInvalidObjectPointer));
 #endif
 }
@@ -1286,7 +1286,6 @@ 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,
@@ -1429,8 +1428,6 @@ void FlowGraphCompiler::EmitEqualityRegRegCompare(Register left,
     if (is_optimizing()) {
       __ CallPatchable(&stub_code->OptimizedIdenticalWithNumberCheckLabel());
     } else {
-      __ movq(R10, Immediate(0));
-      __ movq(RBX, Immediate(0));
       __ CallPatchable(&stub_code->UnoptimizedIdenticalWithNumberCheckLabel());
     }
     if (token_pos != Scanner::kNoSourcePos) {