VM: Make optimized try-catch work in DBC.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
diff --git a/runtime/vm/flow_graph_allocator.cc b/runtime/vm/flow_graph_allocator.cc
index 7b62e3792c3461fd16262c6b9814eb4e6c5622cc..60db301859cdd789889f02bae2815b973f6cd0ab 100644
--- a/runtime/vm/flow_graph_allocator.cc
+++ b/runtime/vm/flow_graph_allocator.cc
@@ -612,10 +612,6 @@ void FlowGraphAllocator::BuildLiveRanges() {
     } else if (block->IsCatchBlockEntry()) {
       // Process initial definitions.
       CatchBlockEntryInstr* catch_entry = block->AsCatchBlockEntry();
-#if defined(TARGET_ARCH_DBC)
-      // TODO(vegorov) support try-catch/finally for DBC.
-      flow_graph_.parsed_function().Bailout("FlowGraphAllocator", "Catch");
-#endif
 
       ProcessEnvironmentUses(catch_entry, catch_entry);  // For lazy deopt
 
@@ -631,10 +627,17 @@ void FlowGraphAllocator::BuildLiveRanges() {
       // block start to until the end of the instruction so that they are
       // preserved.
       intptr_t start = catch_entry->start_pos();
-      BlockLocation(Location::RegisterLocation(kExceptionObjectReg),
+#if !defined(TARGET_ARCH_DBC)
+      intptr_t exception_reg = kExceptionObjectReg;
+      intptr_t stacktrace_reg = kStackTraceObjectReg;
+#else
+      intptr_t exception_reg = -catch_entry->exception_var().index() - 1;

[zra, 2016/10/04 15:22:48]

Can you use LocalVarIndex() in stack_frame_dbc.h

[Florian Schneider, 2016/10/04 17:01:04]

Done. Here and in CatchBlockEntryInstr::EmitNativeCode.

+      intptr_t stacktrace_reg = -catch_entry->stacktrace_var().index() - 1;
+#endif
+      BlockLocation(Location::RegisterLocation(exception_reg),
                     start,
                     ToInstructionEnd(start));
-      BlockLocation(Location::RegisterLocation(kStackTraceObjectReg),
+      BlockLocation(Location::RegisterLocation(stacktrace_reg),
                     start,
                     ToInstructionEnd(start));
     }
@@ -657,8 +660,10 @@ void FlowGraphAllocator::BuildLiveRanges() {
 void FlowGraphAllocator::ProcessInitialDefinition(Definition* defn,
                                                   LiveRange* range,
                                                   BlockEntryInstr* block) {
+#if !defined(TARGET_ARCH_DBC)
   // Save the range end because it may change below.
   intptr_t range_end = range->End();
+#endif
   if (defn->IsParameter()) {
     ParameterInstr* param = defn->AsParameter();
     // Assert that copied and non-copied parameters are mutually exclusive.
@@ -679,7 +684,7 @@ void FlowGraphAllocator::ProcessInitialDefinition(Definition* defn,
       AssignSafepoints(defn, range);
       range->finger()->Initialize(range);
       range->set_assigned_location(Location::RegisterLocation(slot_index));
-      if (range->End() > kNormalEntryPos) {
+      if (block->IsGraphEntry() && range->End() > kNormalEntryPos) {

[zra, 2016/10/04 15:22:48]

Parens around >

[Florian Schneider, 2016/10/04 17:01:04]

Done.

         LiveRange* tail = range->SplitAt(kNormalEntryPos);
         CompleteRange(tail, Location::kRegister);
       }
@@ -726,18 +731,22 @@ void FlowGraphAllocator::ProcessInitialDefinition(Definition* defn,
   }
   ConvertAllUses(range);
   if (defn->IsParameter() && (range->spill_slot().stack_index() >= 0)) {
+#if !defined(TARGET_ARCH_DBC)

[zra, 2016/10/04 15:22:48]

Maybe it would be cleaner to try to use only one #if !defined(TARGET_ARCH_DBC)
here.

[Florian Schneider, 2016/10/04 17:01:04]

Done.

     // Parameters above the frame pointer consume spill slots and are marked
     // in stack maps.
     spill_slots_.Add(range_end);
     quad_spill_slots_.Add(false);
     untagged_spill_slots_.Add(false);
+#endif
     // Note, all incoming parameters are assumed to be tagged.
     MarkAsObjectAtSafepoints(range);
   } else if (defn->IsConstant() && block->IsCatchBlockEntry()) {
+#if !defined(TARGET_ARCH_DBC)
     // Constants at catch block entries consume spill slots.
     spill_slots_.Add(range_end);
     quad_spill_slots_.Add(false);
     untagged_spill_slots_.Add(false);
+#endif
   }
 }