Indirectly dispatch all backtracking jumps through the same block.

runtime/vm/regexp_assembler.cc

 // Copyright (c) 2014, 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/regexp_assembler.h"
 
 #include "vm/bit_vector.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 107 matching lines @@
       new(isolate) JoinEntryInstr(block_id_.Alloc(), kInvalidTryIndex);
   success_block_ =
       new(isolate) JoinEntryInstr(block_id_.Alloc(), kInvalidTryIndex);
   backtrack_block_ =
       new(isolate) JoinEntryInstr(block_id_.Alloc(), kInvalidTryIndex);
   exit_block_ =
       new(isolate) JoinEntryInstr(block_id_.Alloc(), kInvalidTryIndex);
 
   GenerateEntryBlock();
   GenerateSuccessBlock();
-  GenerateBacktrackBlock();
   GenerateExitBlock();
 
   blocks_.Add(entry_block_);
   blocks_.Add(entry_block_->normal_entry());
   blocks_.Add(start_block_);
   blocks_.Add(success_block_);
   blocks_.Add(backtrack_block_);
   blocks_.Add(exit_block_);
 
   // Begin emission at the start_block_.
@@ skipping 62 matching lines @@
   StoreLocal(current_position_, Bind(Sub(start_index_push, length_push)));
 
   // Jump to the start block.
   current_instruction_->Goto(start_block_);
 }
 
 
 void IRRegExpMacroAssembler::GenerateBacktrackBlock() {
   set_current_instruction(backtrack_block_);
   TAG();
-  Backtrack();
+  CheckPreemption();
+
+  const intptr_t entries_count = entry_block_->indirect_entries().length();
+
+  GrowableObjectArray& offsets = GrowableObjectArray::ZoneHandle(
+      I, GrowableObjectArray::New(entries_count, Heap::kOld));
+
+  PushArgumentInstr* block_offsets_push =
+      PushArgument(Bind(new(I) ConstantInstr(offsets)));
+  PushArgumentInstr* block_id_push = PushArgument(PopStack());
+
+  Value* offset_value =
+      Bind(InstanceCall(InstanceCallDescriptor::FromToken(Token::kINDEX),
+                        block_offsets_push,
+                        block_id_push));
+
+  backtrack_goto_ = new(I) IndirectGotoInstr(&offsets, offset_value);
+  CloseBlockWith(backtrack_goto_);
+
+  // Add an edge from the "indirect" goto to each of the targets.
+  for (intptr_t j = 0; j < entries_count; j++) {
+    backtrack_goto_->AddSuccessor(
+        TargetWithJoinGoto(entry_block_->indirect_entries().At(j)));
+  }
 }
 
 
 void IRRegExpMacroAssembler::GenerateSuccessBlock() {
   set_current_instruction(success_block_);
   TAG();
 
   Definition* type_args_null_def = new(I) ConstantInstr(
         TypeArguments::ZoneHandle(I, TypeArguments::null()));
   PushArgumentInstr* type_arg_push = PushArgument(Bind(type_args_null_def));
@@ skipping 494 matching lines @@
   if (by != 0) {
     PushArgumentInstr* reg_push = PushLocal(position_register(reg));
     PushArgumentInstr* by_push = PushArgument(Bind(Int64Constant(by)));
     StoreLocal(position_register(reg), Bind(Add(reg_push, by_push)));
   }
 }
 
 
 void IRRegExpMacroAssembler::Backtrack() {
   TAG();
-  CheckPreemption();
-
-  GrowableObjectArray& offsets = GrowableObjectArray::ZoneHandle(
-        I, GrowableObjectArray::New(Heap::kOld));
-
-  PushArgumentInstr* block_offsets_push =
-      PushArgument(Bind(new(I) ConstantInstr(offsets)));
-  PushArgumentInstr* block_id_push = PushArgument(PopStack());
-
-  Value* offset_value =
-      Bind(InstanceCall(InstanceCallDescriptor::FromToken(Token::kINDEX),
-                        block_offsets_push,
-                        block_id_push));
-
-  IndirectGotoInstr* igoto = new(I) IndirectGotoInstr(&offsets, offset_value);
-  CloseBlockWith(igoto);
-  igotos_.Add(igoto);
+  GoTo(backtrack_block_);
 }
 
 
 // A BindBlock is analogous to assigning a label to a basic block.
 // If the BlockLabel does not yet contain a block, it is created.
 // If there is a current instruction, append a goto to the bound block.
 void IRRegExpMacroAssembler::BindBlock(BlockLabel* label) {
   ASSERT(!label->IsBound());
   ASSERT(label->block()->next() == NULL);
 
@@ skipping 19 matching lines @@
 LocalVariable* IRRegExpMacroAssembler::position_register(intptr_t index) {
   // Create position registers as needed.
   for (intptr_t i = position_registers_.length(); i < index + 1; i++) {
     position_registers_.Add(Local(Symbols::position_registers_()));
   }
 
   return position_registers_[index];
 }
 
 
-// TODO(zerny): Move the offset table outside to avoid having to keep
-// the assembler around until after code generation; both function or regexp
-// would work.
-void IRRegExpMacroAssembler::FinalizeBlockOffsetTable() {
-  for (intptr_t i = 0; i < igotos_.length(); i++) {
-    IndirectGotoInstr* igoto = igotos_[i];
-    igoto->SetOffsetCount(I, indirect_id_.Count());
-
-    for (intptr_t j = 0; j < igoto->SuccessorCount(); j++) {
-      TargetEntryInstr* target = igoto->SuccessorAt(j);
-
-      // Optimizations might have modified the immediate target block, but
-      // it must end with a goto to the indirect entry.
-      Instruction* instr = target;
-      while (instr != NULL && !instr->IsGoto()) {
-        instr = instr->next();
-      }
-      ASSERT(instr->IsGoto());
-
-      IndirectEntryInstr* ientry =
-          instr->AsGoto()->successor()->AsIndirectEntry();
-      ASSERT(ientry != NULL);
-
-      // The intermediate block was possibly compacted, check both it and the
-      // final indirect entry for a valid offset. If neither are valid, then
-      // the indirect entry is unreachable.
-      intptr_t offset =
-          (target->offset() > 0) ? target->offset() : ientry->offset();
-      if (offset > 0) {
-        intptr_t adjusted_offset =
-            offset - Assembler::EntryPointToPcMarkerOffset();
-        igoto->SetOffsetAt(I, ientry->indirect_id(), adjusted_offset);
-      }
-    }
-  }
-}
-
-void IRRegExpMacroAssembler::FinalizeIndirectGotos() {
-  for (intptr_t i = 0; i < igotos_.length(); i++) {
-    for (intptr_t j = 0; j < entry_block_->indirect_entries().length(); j++) {
-      igotos_.At(i)->AddSuccessor(
-            TargetWithJoinGoto(entry_block_->indirect_entries().At(j)));
-    }
-  }
-}
-
-
 void IRRegExpMacroAssembler::CheckCharacter(uint32_t c, BlockLabel* on_equal) {
   TAG();
   Definition* cur_char_def = LoadLocal(current_character_);
   Definition* char_def = Uint64Constant(c);
 
   BranchOrBacktrack(Comparison(kEQ, cur_char_def, char_def),
                     on_equal);
 }
 
 
@@ skipping 1005 matching lines @@
       index,
       characters,
       specialization_cid_,
       Scanner::kNoSourcePos));
 }
 
 
 #undef __
 
 }  // namespace dart