VM: Make optimized try-catch work in DBC.

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2013, 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/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/log.h"
 #include "vm/parser.h"
+#include "vm/stack_frame.h"
 
 namespace dart {
 
 #if defined(DEBUG)
 #define TRACE_ALLOC(statement)                                                 \
   do {                                                                         \
     if (FLAG_trace_ssa_allocator) statement;                                   \
   } while (0)
 #else
 #define TRACE_ALLOC(statement)
@@ skipping 581 matching lines @@
           range->MarkHasOnlyUnconstrainedUsesInLoop(block_info->loop_id());
         }
       }
     }
 
     if (block->IsJoinEntry()) {
       ConnectIncomingPhiMoves(block->AsJoinEntry());
     } 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
 
       for (intptr_t i = 0;
            i < catch_entry->initial_definitions()->length();
            i++) {
         Definition* defn = (*catch_entry->initial_definitions())[i];
         LiveRange* range = GetLiveRange(defn->ssa_temp_index());
         range->DefineAt(catch_entry->start_pos());  // Defined at block entry.
         ProcessInitialDefinition(defn, range, catch_entry);
       }
       // Block the two fixed registers used by CatchBlockEntryInstr from the
       // 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)
+      const Register exception_reg = kExceptionObjectReg;
+      const Register stacktrace_reg = kStackTraceObjectReg;
+#else
+      const intptr_t exception_reg =
+          LocalVarIndex(0, catch_entry->exception_var().index());
+      const intptr_t stacktrace_reg =
+          LocalVarIndex(0, catch_entry->stacktrace_var().index());
+#endif
+      BlockLocation(Location::RegisterLocation(exception_reg),
                     start,
                     ToInstructionEnd(start));
-      BlockLocation(Location::RegisterLocation(kStackTraceObjectReg),
+      BlockLocation(Location::RegisterLocation(stacktrace_reg),
                     start,
                     ToInstructionEnd(start));
     }
   }
 
   // Process incoming parameters and constants.  Do this after all other
   // instructions so that safepoints for all calls have already been found.
   GraphEntryInstr* graph_entry = flow_graph_.graph_entry();
   for (intptr_t i = 0; i < graph_entry->initial_definitions()->length(); i++) {
     Definition* defn = (*graph_entry->initial_definitions())[i];
     ASSERT(!defn->HasPairRepresentation());
     LiveRange* range = GetLiveRange(defn->ssa_temp_index());
     range->AddUseInterval(graph_entry->start_pos(), graph_entry->end_pos());
     range->DefineAt(graph_entry->start_pos());
     ProcessInitialDefinition(defn, range, graph_entry);
   }
 }
 
 
 void FlowGraphAllocator::ProcessInitialDefinition(Definition* defn,
                                                   LiveRange* range,
                                                   BlockEntryInstr* block) {
+#if defined(TARGET_ARCH_DBC)
+  if (block->IsCatchBlockEntry()) {
+    if (defn->IsParameter()) {
+      ParameterInstr* param = defn->AsParameter();
+      intptr_t slot_index = param->index();
+      AssignSafepoints(defn, range);
+      range->finger()->Initialize(range);
+      slot_index = kNumberOfCpuRegisters - 1 - slot_index;
+      range->set_assigned_location(Location::RegisterLocation(slot_index));

[Vyacheslav Egorov (Google), 2016/10/13 15:02:04]

Some of this code is repeated below just with  kNormalEntryPos instead of
block->lifetime_position() + 2. 

I wonder if it can be refactored into a separate helper method. 

[Florian Schneider, 2016/10/13 17:24:03]

Done.

+      if (range->End() > block->lifetime_position() + 2) {
+        LiveRange* tail = range->SplitAt(block->lifetime_position() + 2);
+        CompleteRange(tail, Location::kRegister);
+      }
+      ConvertAllUses(range);
+      BlockLocation(Location::RegisterLocation(slot_index), 0, kMaxPosition);
+    } else {
+      ConstantInstr* constant = defn->AsConstant();
+      ASSERT(constant != NULL);
+      range->set_assigned_location(Location::Constant(constant));
+      range->set_spill_slot(Location::Constant(constant));
+      AssignSafepoints(defn, range);
+      range->finger()->Initialize(range);
+      UsePosition* use =
+          range->finger()->FirstRegisterBeneficialUse(block->start_pos());
+      if (use != NULL) {
+        LiveRange* tail =
+            SplitBetween(range, block->start_pos(), use->pos());
+        // Parameters and constants are tagged, so allocated to CPU registers.
+        CompleteRange(tail, Location::kRegister);

[Vyacheslav Egorov (Google), 2016/10/13 15:02:04]

we have UnboxedConstantInstr (which inherits from ConstantInstr), so maybe
assert representation, just in case?

[Florian Schneider, 2016/10/13 17:24:03]

Done.

+      }
+      ConvertAllUses(range);
+    }
+    return;
+  }
+#endif
+
   // Save the range end because it may change below.
   intptr_t range_end = range->End();
   if (defn->IsParameter()) {
     ParameterInstr* param = defn->AsParameter();
     // Assert that copied and non-copied parameters are mutually exclusive.
     // This might change in the future and, if so, the index will be wrong.
     ASSERT((flow_graph_.num_copied_params() == 0) ||
            (flow_graph_.num_non_copied_params() == 0));
     intptr_t slot_index = param->index();
     ASSERT((param->base_reg() == FPREG) || (param->base_reg() == SPREG));
@@ skipping 2443 matching lines @@
       FlowGraphPrinter printer(flow_graph_, true);
       printer.PrintBlocks();
 #endif
     }
     THR_Print("----------------------------------------------\n");
   }
 }
 
 
 }  // namespace dart