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

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
===================================================================
--- runtime/vm/intermediate_language_x64.cc	(revision 10885)
+++ runtime/vm/intermediate_language_x64.cc	(working copy)
@@ -2143,6 +2143,47 @@
   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 __