VM: Make optimized try-catch work in DBC.

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 aca13bdda4f4d677e5fae7d59cca94a1699c7b3f..cbcd5875f623c13505e0022ebc9220139f796a27 100644
--- a/runtime/vm/intermediate_language_dbc.cc
+++ b/runtime/vm/intermediate_language_dbc.cc
@@ -1119,9 +1119,14 @@ EMIT_NATIVE_CODE(CatchBlockEntry, 0) {
                                 compiler->assembler()->CodeSize(),
                                 catch_handler_types_,
                                 needs_stacktrace());
-  __ MoveSpecial(-exception_var().index()-1,
+
+  if (HasParallelMove()) {
+    compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
+  }
+
+  __ MoveSpecial(LocalVarIndex(0, exception_var().index()),
                  Simulator::kExceptionSpecialIndex);
-  __ MoveSpecial(-stacktrace_var().index()-1,
+  __ MoveSpecial(LocalVarIndex(0, stacktrace_var().index()),
                  Simulator::kStacktraceSpecialIndex);
   __ SetFrame(compiler->StackSize());
 }
@@ -1400,10 +1405,15 @@ EMIT_NATIVE_CODE(CheckClass, 1) {
            (unary_checks().NumberOfChecks() > 1));
     const intptr_t may_be_smi =
         (unary_checks().GetReceiverClassIdAt(0) == kSmiCid) ? 1 : 0;
+    bool is_dense_switch = false;
+    intptr_t cid_mask = 0;
     if (IsDenseSwitch()) {
       ASSERT(cids_[0] < cids_[cids_.length() - 1]);
+      cid_mask = ComputeCidMask();
+      is_dense_switch = Smi::IsValid(cid_mask);

[Florian Schneider, 2016/10/04 17:07:57]

I'll fix this in a follow-up CL by adding support for adding untagged immediates
to the constant pool. For now, just bail out to the generic CheckClass if mask
is too large for a smi.

+    }
+    if (is_dense_switch) {
       const intptr_t low_cid = cids_[0];
-      const intptr_t cid_mask = ComputeCidMask();
       __ CheckDenseSwitch(value, may_be_smi);
       __ Nop(compiler->ToEmbeddableCid(low_cid, this));
       __ Nop(__ AddConstant(Smi::Handle(Smi::New(cid_mask))));