Precompilation: Generate instance calls as IC calls that can switch to Megamoprhic calls.

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 2a80633d890a0e31ddade5801d90ad33788bb3c8..42b3677bc82c3adf48a372fd084373708321f716 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -1286,20 +1286,17 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
   ASSERT(!arguments_descriptor.IsNull() && (arguments_descriptor.Length() > 0));
   const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(zone(),
       MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
-  const Register receiverR = RDI;
-  const Register cacheR = RBX;
-  const Register targetR = RCX;
-  __ movq(receiverR, Address(RSP, (argument_count - 1) * kWordSize));
-  __ LoadObject(cacheR, cache);
 
+  __ Comment("MegamorphicCall");
+  __ movq(RDI, Address(RSP, (argument_count - 1) * kWordSize));
+  __ LoadObject(RBX, cache);
   if (FLAG_use_megamorphic_stub) {
     __ Call(*StubCode::MegamorphicLookup_entry());
   } else  {
-    StubCode::EmitMegamorphicLookup(assembler(), receiverR, cacheR, targetR);
+    StubCode::EmitMegamorphicLookup(assembler());
   }
-  __ LoadObject(RBX, ic_data);
-  __ LoadObject(R10, arguments_descriptor);
-  __ call(targetR);
+  __ call(RCX);
+
   AddCurrentDescriptor(RawPcDescriptors::kOther,
       Thread::kNoDeoptId, token_pos);
   RecordSafepoint(locs);
@@ -1315,6 +1312,46 @@ void FlowGraphCompiler::EmitMegamorphicInstanceCall(
 }
 
 
+void FlowGraphCompiler::EmitSwitchableInstanceCall(
+    const ICData& ic_data,
+    intptr_t argument_count,
+    intptr_t deopt_id,
+    intptr_t token_pos,
+    LocationSummary* locs) {
+  __ Comment("SwitchableCall");
+  __ movq(RDI, Address(RSP, (argument_count - 1) * kWordSize));
+  if (ic_data.NumArgsTested() == 1) {
+    __ LoadUniqueObject(RBX, ic_data);
+    __ CallPatchable(*StubCode::ICLookup_entry());
+  } else {
+    const String& name = String::Handle(zone(), ic_data.target_name());
+    const Array& arguments_descriptor =
+        Array::ZoneHandle(zone(), ic_data.arguments_descriptor());
+    ASSERT(!arguments_descriptor.IsNull() &&
+           (arguments_descriptor.Length() > 0));
+    const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(zone(),
+        MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
+
+    __ LoadUniqueObject(RBX, cache);
+    __ CallPatchable(*StubCode::MegamorphicLookup_entry());
+  }
+  __ call(RCX);
+
+  AddCurrentDescriptor(RawPcDescriptors::kOther,
+                       Thread::kNoDeoptId, token_pos);
+  RecordSafepoint(locs);
+  const intptr_t deopt_id_after = Thread::ToDeoptAfter(deopt_id);
+  if (is_optimizing()) {
+    AddDeoptIndexAtCall(deopt_id_after, token_pos);
+  } else {
+    // Add deoptimization continuation point after the call and before the
+    // arguments are removed.
+    AddCurrentDescriptor(RawPcDescriptors::kDeopt, deopt_id_after, token_pos);
+  }
+  __ Drop(argument_count, RCX);
+}
+
+
 void FlowGraphCompiler::EmitOptimizedStaticCall(
     const Function& function,
     const Array& arguments_descriptor,