DBC: CheckClassInstr

runtime/vm/intermediate_language_dbc.cc

Index: runtime/vm/intermediate_language_dbc.cc
diff --git a/runtime/vm/intermediate_language_dbc.cc b/runtime/vm/intermediate_language_dbc.cc
index d28bbb2c30aff544c47e1e37ad46739edb5d8879..f9fd3f620a984dee168d4a9b79a544f44d5bfa9d 100644
--- a/runtime/vm/intermediate_language_dbc.cc
+++ b/runtime/vm/intermediate_language_dbc.cc
@@ -105,7 +105,6 @@ DECLARE_FLAG(int, optimization_counter_threshold);
   M(UnboxInteger32)                                                            \
   M(CheckedSmiOp)                                                              \
   M(CheckArrayBound)                                                           \
-  M(CheckClass)                                                                \
   M(TestSmi)                                                                   \
   M(RelationalOp)                                                              \
   M(EqualityCompare)                                                           \
@@ -481,6 +480,13 @@ void BranchInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 
 
 EMIT_NATIVE_CODE(Goto, 0) {
+  if (!compiler->is_optimizing()) {
+    // Add a deoptimization descriptor for deoptimizing instructions that
+    // may be inserted before this instruction.
+    compiler->AddCurrentDescriptor(RawPcDescriptors::kDeopt,
+                                   GetDeoptId(),
+                                   TokenPosition::kNoSource);
+  }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
   }
@@ -945,6 +951,34 @@ EMIT_NATIVE_CODE(CheckClassId, 1) {
 }
 
 
+EMIT_NATIVE_CODE(CheckClass, 1) {
+  const Register value = locs()->in(0).reg();
+  if (IsNullCheck()) {
+    ASSERT(DeoptIfNull() || DeoptIfNotNull());
+    __ CheckNull(value, DeoptIfNull() ? 1 : 0);
+    compiler->EmitDeopt(deopt_id(),
+                        ICData::kDeoptCheckClass,
+                        licm_hoisted_ ? ICData::kHoisted : 0);
+    return;
+  }
+
+  ASSERT((unary_checks().GetReceiverClassIdAt(0) != kSmiCid) ||
+         (unary_checks().NumberOfChecks() > 1));
+  const intptr_t ic_data = __ AddConstant(unary_checks());
+  if (IsDenseSwitch()) {
+    ASSERT(cids_[0] < cids_[cids_.length() - 1]);
+    __ PushConstant(Smi::Handle(Smi::New(cids_[0])));

[Vyacheslav Egorov (Google), 2016/06/28 13:03:10]

This encoding of the dense switch is suboptimal. I suggest encoding it like
this:

CheckDenseSwitchTOS rA, CanBeSmi
Nop cids[0] 
Nop ComputeCidMask()
Deopt ...

CheckDenseSwitchTOS would then look ahead and decode low and mask from
subsequent NOPs.

If Check succeeds we skip 3 instructions if check fails we skip 2. 

WDYT?

[zra, 2016/06/28 19:31:40]

It looks like cids can be 32-bits, so I think those constants have to go in the
pool, but getting rid of the PushConstants makes sense.

+    __ PushConstant(Smi::Handle(Smi::New(ComputeCidMask())));
+    __ CheckDenseSwitchTOS(value, ic_data);
+  } else {
+    __ CheckForCid(value, ic_data);

[Vyacheslav Egorov (Google), 2016/06/28 13:03:10]

Similar note here. I suggest making this very fast (= no additional memory
loads) for the 1 check. I suggest splitting it into 

CheckCid value, cid

and 

CheckCids value, icdata

for starters.

[zra, 2016/06/28 19:31:40]

Done.

+  }
+  compiler->EmitDeopt(deopt_id(),
+                  ICData::kDeoptCheckClass,

[Vyacheslav Egorov (Google), 2016/06/28 13:03:10]

Indentation. 

Can this be shared with NullCheck case?

if (IsNullCheck()) {
  ...
} else if (IsDenseSwitch()) {
  ...
} else {
  ...
}
compiler->EmitDeopt(...);

[zra, 2016/06/28 19:31:40]

Done.

+                  licm_hoisted_ ? ICData::kHoisted : 0);
+}
+
+
 EMIT_NATIVE_CODE(BinarySmiOp, 2, Location::RequiresRegister()) {
   const Register left = locs()->in(0).reg();
   const Register right = locs()->in(1).reg();