Cache lookups at megamorphic call sites in optimized code.

runtime/vm/stub_code_x64.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
 #include "vm/compiler.h"
@@ skipping 542 matching lines @@
   __ pushq(RBX);
   GenerateDeoptimizationSequence(assembler, true);  // Preserve RAX.
 }
 
 
 void StubCode::GenerateDeoptimizeStub(Assembler* assembler) {
   GenerateDeoptimizationSequence(assembler, false);  // Don't preserve RAX.
 }
 
 
+void StubCode::GenerateMegamorphicMissStub(Assembler* assembler) {
+  const Immediate raw_null =
+      Immediate(reinterpret_cast<intptr_t>(Instructions::null()));
+  AssemblerMacros::EnterStubFrame(assembler);
+  __ pushq(raw_null);  // Space for the result of the runtime call.
+  // Load the receiver into RAX.  The argument count in the arguments
+  // descriptor is a smi.
+  __ movq(RAX, FieldAddress(R10, Array::data_offset()));
+  // Three words in the stack above the last argument.
+  __ movq(RAX, Address(RSP, RAX, TIMES_4, 3 * kWordSize));
+  __ pushq(RAX);  // Receiver.
+  __ pushq(RBX);  // IC data.
+  __ pushq(R10);  // Arguments descriptor.
+  __ CallRuntime(kMegamorphicCacheMissHandlerRuntimeEntry);
+  __ popq(R10);  // Arguments descriptor.
+  __ popq(RBX);  // IC data.
+  __ popq(RAX);  // Discard.
+  __ popq(RAX);  // Return value from the runtime call (instructions).
+  __ LeaveFrame();
+
+  Label lookup;
+  __ cmpq(RAX, raw_null);
+  __ j(EQUAL, &lookup, Assembler::kNearJump);
+  __ addq(RAX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
+  __ jmp(RAX);
+
+  __ Bind(&lookup);
+  __ int3();
+  __ jmp(&StubCode::InstanceFunctionLookupLabel());
+}
+
+
+
 // Called for inline allocation of arrays.
 // Input parameters:
 //   R10 : Array length as Smi.
 //   RBX : array element type (either NULL or an instantiated type).
 // NOTE: R10 cannot be clobbered here as the caller relies on it being saved.
 // The newly allocated object is returned in RAX.
 void StubCode::GenerateAllocateArrayStub(Assembler* assembler) {
   Label slow_case;
   const Immediate raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
@@ skipping 1590 matching lines @@
   __ cmpq(left, right);
   __ Bind(&done);
   __ popq(right);
   __ popq(left);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64