Implement class id checks as a separate instruction and add a local CSE optimization pass.

runtime/vm/intermediate_language_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"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 2125 matching lines @@
                                  try_index(),
                                  function_name,
                                  kNumArguments,
                                  Array::ZoneHandle(),  // No optional arguments.
                                  kNumArgsChecked,
                                  locs()->stack_bitmap());
   __ CompareObject(RAX, compiler->bool_true());
   EmitBranchOnCondition(compiler, branch_condition);
 }
 
+
+LocationSummary* CheckClassComp::MakeLocationSummary() const {
+  const intptr_t kNumInputs = 1;
+  const intptr_t kNumTemps = 1;
+  LocationSummary* summary =
+      new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kNoCall);
+  summary->set_in(0, Location::RequiresRegister());
+  summary->set_temp(0, Location::RequiresRegister());
+  return summary;
+}
+
+
+void CheckClassComp::EmitNativeCode(FlowGraphCompiler* compiler) {

[srdjan, 2012/08/17 22:30:22]

Maybe make this code more generic so that it can handle Smi's as well (TODO is
OK for now). We should also use it for Smi checks as well, shouldn't we.

[Florian Schneider, 2012/08/20 12:09:37]

CheckSmi would fit in here, but for CheckNonSmi we'd need a separate
instruction. So maybe we should just have a separate check that checks either
for smi or non-smi.

+  Register value = locs()->in(0).reg();
+  Register temp = locs()->temp(0).reg();
+  Label* deopt = compiler->AddDeoptStub(deopt_id(),
+                                        try_index(),
+                                        kDeoptCheckClass,
+                                        value);
+  ASSERT(ic_data()->GetReceiverClassIdAt(0) != kSmiCid);
+  __ testq(value, Immediate(kSmiTagMask));
+  __ j(ZERO, deopt);
+  __ LoadClassId(temp, value);
+  Label is_ok;
+  const intptr_t num_checks = ic_data()->NumberOfChecks();
+  const bool use_near_jump = num_checks < 5;
+  for (intptr_t i = 0; i < num_checks; i++) {
+    __ cmpl(temp, Immediate(ic_data()->GetReceiverClassIdAt(i)));
+    if (i == (num_checks - 1)) {
+      __ j(NOT_EQUAL, deopt);
+    } else {
+      if (use_near_jump) {
+        __ j(EQUAL, &is_ok, Assembler::kNearJump);
+      } else {
+        __ j(EQUAL, &is_ok);
+      }
+    }
+  }
+  __ Bind(&is_ok);
+}
+
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64