Faster checks in polymorphic instance calls if Smi-s are involved

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 8627315296a9e223ea58b9d97eb696c85962f711..649e9190624fc013184ec546faea37bfca0f9251 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -1471,33 +1471,77 @@ void FlowGraphCompiler::ClobberDeadTempRegisters(LocationSummary* locs) {
 
 
 void FlowGraphCompiler::EmitTestAndCall(const ICData& ic_data,
-                                        Register class_id_reg,
                                         intptr_t argument_count,
                                         const Array& argument_names,
-                                        Label* deopt,
+                                        Label* failed,
+                                        Label* match_found,
                                         intptr_t deopt_id,
                                         intptr_t token_index,
                                         LocationSummary* locs) {
   ASSERT(is_optimizing());
-  ASSERT(!ic_data.IsNull() && (ic_data.NumberOfUsedChecks() > 0));
-  Label match_found;
-  const intptr_t len = ic_data.NumberOfChecks();
-  GrowableArray<CidTarget> sorted(len);
-  SortICDataByCount(ic_data, &sorted, /* drop_smi = */ false);
-  ASSERT(class_id_reg != R10);
-  ASSERT(len > 0);  // Why bother otherwise.
+
+  __ Comment("EmitTestAndCall");
   const Array& arguments_descriptor =
       Array::ZoneHandle(ArgumentsDescriptor::New(argument_count,
                                                  argument_names));
   StubCode* stub_code = isolate()->stub_code();
-
+  // Load receiver into RAX.
+  __ movq(RAX,
+      Address(RSP, (argument_count - 1) * kWordSize));
   __ LoadObject(R10, arguments_descriptor, PP);
-  for (intptr_t i = 0; i < len; i++) {
-    const bool is_last_check = (i == (len - 1));
+
+  const bool kFirstCheckIsSmi = ic_data.GetReceiverClassIdAt(0) == kSmiCid;
+  const intptr_t kNumChecks = ic_data.NumberOfChecks();
+
+  ASSERT(!ic_data.IsNull() && (kNumChecks > 0));
+
+  Label after_smi_test;
+  __ testq(RAX, Immediate(kSmiTagMask));
+  if (kFirstCheckIsSmi) {
+    // Jump if receiver is not Smi.
+    if (kNumChecks == 1) {
+      __ j(NOT_ZERO, failed);
+    } else {
+      __ j(NOT_ZERO, &after_smi_test);
+    }
+    // Do not use the code from the function, but let the code be patched so
+    // that we can record the outgoing edges to other code.
+    GenerateDartCall(deopt_id,
+                     token_index,
+                     &stub_code->CallStaticFunctionLabel(),
+                     RawPcDescriptors::kOther,
+                     locs);
+    const Function& function = Function::Handle(ic_data.GetTargetAt(0));
+    AddStaticCallTarget(function);
+    __ Drop(argument_count, RCX);
+    if (kNumChecks > 1) {
+      __ jmp(match_found);
+    }
+  } else {
+    // Receiver is Smi, but Smi is not a valid class therefore fail.
+    // (Smi class must be first in the list).
+    __ j(ZERO, failed);
+  }
+  __ Bind(&after_smi_test);
+
+  ASSERT(!ic_data.IsNull() && (kNumChecks > 0));
+  GrowableArray<CidTarget> sorted(kNumChecks);
+  SortICDataByCount(ic_data, &sorted, /* drop_smi = */ true);
+
+  const intptr_t kSortedLen = sorted.length();
+  // If kSortedLen is 0 then only a Smi check was needed; the Smi check above
+  // will fail if there was only one check and receiver is not Smi.
+  if (kSortedLen == 0) return;
+
+  // Value is not Smi,
+  __ LoadClassId(RDI, RAX);
+  for (intptr_t i = 0; i < kSortedLen; i++) {
+    const bool kIsLastCheck = (i == (kSortedLen - 1));
+    ASSERT(sorted[i].cid != kSmiCid);
     Label next_test;
-    __ cmpl(class_id_reg, Immediate(sorted[i].cid));
-    if (is_last_check) {
-      __ j(NOT_EQUAL, deopt);
+    __ cmpl(RDI, Immediate(sorted[i].cid));
+    if (kIsLastCheck) {
+      __ j(NOT_EQUAL, failed);
     } else {
       __ j(NOT_EQUAL, &next_test);
     }
@@ -1511,12 +1555,11 @@ void FlowGraphCompiler::EmitTestAndCall(const ICData& ic_data,
     const Function& function = *sorted[i].target;
     AddStaticCallTarget(function);
     __ Drop(argument_count, RCX);
-    if (!is_last_check) {
-      __ jmp(&match_found);
+    if (!kIsLastCheck) {
+      __ jmp(match_found);
     }
     __ Bind(&next_test);
   }
-  __ Bind(&match_found);
 }