Indirectly dispatch all backtracking jumps through the same block.

runtime/vm/intermediate_language.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/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
@@ skipping 2512 matching lines @@
     compiler->AddCurrentDescriptor(RawPcDescriptors::kDeopt,
                                    GetDeoptId(),
                                    Scanner::kNoSourcePos);
   }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
   }
 }
 
 
+void IndirectGotoInstr::ComputeOffsetTable(Isolate* isolate) {
+  if (GetBlock()->offset() < 0) {
+    // Don't generate a table when contained in an unreachable block.
+    return;
+  }
+  ASSERT(SuccessorCount() == offsets_.Capacity());
+  offsets_.SetLength(SuccessorCount());
+  for (intptr_t i = 0; i < SuccessorCount(); i++) {
+    TargetEntryInstr* target = SuccessorAt(i);
+    intptr_t offset = target->offset();
+
+    // The intermediate block might be compacted, if so, use the indirect entry.
+    if (offset < 0) {
+      // Optimizations might have modified the immediate target block, but it
+      // must end with a goto to the indirect entry. Also, we can't use
+      // last_instruction because 'target' is compacted/unreachable.
+      Instruction* last = target->next();
+      while (last != NULL && !last->IsGoto()) {
+        last = last->next();
+      }
+      ASSERT(last);
+      IndirectEntryInstr* ientry =
+          last->AsGoto()->successor()->AsIndirectEntry();
+      ASSERT(ientry != NULL);
+      ASSERT(ientry->indirect_id() == i);
+      offset = ientry->offset();
+    }
+
+    ASSERT(offset > 0);
+    offset -= Assembler::EntryPointToPcMarkerOffset();
+    offsets_.SetAt(i, Smi::ZoneHandle(isolate, Smi::New(offset)));
+  }
+}
+
+
 LocationSummary* IndirectEntryInstr::MakeLocationSummary(
     Isolate* isolate, bool optimizing) const {
   return JoinEntryInstr::MakeLocationSummary(isolate, optimizing);
 }
 
 
 void IndirectEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   JoinEntryInstr::EmitNativeCode(compiler);
 }
 
@@ skipping 835 matching lines @@
     case Token::kTRUNCDIV: return 0;
     case Token::kMOD: return 1;
     default: UNIMPLEMENTED(); return -1;
   }
 }
 
 
 #undef __
 
 }  // namespace dart