[crankshaft] Delete unused Hydrogen-BCH code

src/crankshaft/hydrogen-bch.cc

Index: src/crankshaft/hydrogen-bch.cc
diff --git a/src/crankshaft/hydrogen-bch.cc b/src/crankshaft/hydrogen-bch.cc
deleted file mode 100644
index 060e0bcdabb488c6181ea72906a6f722040235b0..0000000000000000000000000000000000000000
--- a/src/crankshaft/hydrogen-bch.cc
+++ /dev/null
@@ -1,379 +0,0 @@
-// Copyright 2013 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "src/crankshaft/hydrogen-bch.h"
-
-namespace v8 {
-namespace internal {
-
-/*
- * This class is a table with one element for eack basic block.
- *
- * It is used to check if, inside one loop, all execution paths contain
- * a bounds check for a particular [index, length] combination.
- * The reason is that if there is a path that stays in the loop without
- * executing a check then the check cannot be hoisted out of the loop (it
- * would likely fail and cause a deopt for no good reason).
- * We also check is there are paths that exit the loop early, and if yes we
- * perform the hoisting only if graph()->use_optimistic_licm() is true.
- * The reason is that such paths are realtively common and harmless (like in
- * a "search" method that scans an array until an element is found), but in
- * some cases they could cause a deopt if we hoist the check so this is a
- * situation we need to detect.
- */
-class InductionVariableBlocksTable BASE_EMBEDDED {
- public:
-  class Element {
-   public:
-    static const int kNoBlock = -1;
-
-    HBasicBlock* block() { return block_; }
-    void set_block(HBasicBlock* block) { block_ = block; }
-    bool is_start() { return is_start_; }
-    bool is_proper_exit() { return is_proper_exit_; }
-    bool is_in_loop() { return is_in_loop_; }
-    bool has_check() { return has_check_; }
-    void set_has_check() { has_check_ = true; }
-    InductionVariableLimitUpdate* additional_limit() {
-      return &additional_limit_;
-    }
-
-    /*
-     * Initializes the table element for a given loop (identified by its
-     * induction variable).
-     */
-    void InitializeLoop(InductionVariableData* data) {
-      DCHECK(data->limit() != NULL);
-      HLoopInformation* loop = data->phi()->block()->current_loop();
-      is_start_ = (block() == loop->loop_header());
-      is_proper_exit_ = (block() == data->induction_exit_target());
-      is_in_loop_ = loop->IsNestedInThisLoop(block()->current_loop());
-      has_check_ = false;
-    }
-
-    // Utility methods to iterate over dominated blocks.
-    void ResetCurrentDominatedBlock() { current_dominated_block_ = kNoBlock; }
-    HBasicBlock* CurrentDominatedBlock() {
-      DCHECK(current_dominated_block_ != kNoBlock);
-      return current_dominated_block_ < block()->dominated_blocks()->length() ?
-          block()->dominated_blocks()->at(current_dominated_block_) : NULL;
-    }
-    HBasicBlock* NextDominatedBlock() {
-      current_dominated_block_++;
-      return CurrentDominatedBlock();
-    }
-
-    Element()
-        : block_(NULL), is_start_(false), is_proper_exit_(false),
-          has_check_(false), additional_limit_(),
-          current_dominated_block_(kNoBlock) {}
-
-   private:
-    HBasicBlock* block_;
-    bool is_start_;
-    bool is_proper_exit_;
-    bool is_in_loop_;
-    bool has_check_;
-    InductionVariableLimitUpdate additional_limit_;
-    int current_dominated_block_;
-  };
-
-  HGraph* graph() const { return graph_; }
-  Counters* counters() const { return graph()->isolate()->counters(); }
-  HBasicBlock* loop_header() const { return loop_header_; }
-  Element* at(int index) const { return &(elements_.at(index)); }
-  Element* at(HBasicBlock* block) const { return at(block->block_id()); }
-
-  void AddCheckAt(HBasicBlock* block) {
-    at(block->block_id())->set_has_check();
-  }
-
-  /*
-   * Initializes the table for a given loop (identified by its induction
-   * variable).
-   */
-  void InitializeLoop(InductionVariableData* data) {
-    for (int i = 0; i < graph()->blocks()->length(); i++) {
-      at(i)->InitializeLoop(data);
-    }
-    loop_header_ = data->phi()->block()->current_loop()->loop_header();
-  }
-
-
-  enum Hoistability {
-    HOISTABLE,
-    OPTIMISTICALLY_HOISTABLE,
-    NOT_HOISTABLE
-  };
-
-  /*
-   * This method checks if it is appropriate to hoist the bounds checks on an
-   * induction variable out of the loop.
-   * The problem is that in the loop code graph there could be execution paths
-   * where the check is not performed, but hoisting the check has the same
-   * semantics as performing it at every loop iteration, which could cause
-   * unnecessary check failures (which would mean unnecessary deoptimizations).
-   * The method returns OK if there are no paths that perform an iteration
-   * (loop back to the header) without meeting a check, or UNSAFE is set if
-   * early exit paths are found.
-   */
-  Hoistability CheckHoistability() {
-    for (int i = 0; i < elements_.length(); i++) {
-      at(i)->ResetCurrentDominatedBlock();
-    }
-    bool unsafe = false;
-
-    HBasicBlock* current = loop_header();
-    while (current != NULL) {
-      HBasicBlock* next;
-
-      if (at(current)->has_check() || !at(current)->is_in_loop()) {
-        // We found a check or we reached a dominated block out of the loop,
-        // therefore this block is safe and we can backtrack.
-        next = NULL;
-      } else {
-        for (int i = 0; i < current->end()->SuccessorCount(); i ++) {
-          Element* successor = at(current->end()->SuccessorAt(i));
-
-          if (!successor->is_in_loop()) {
-            if (!successor->is_proper_exit()) {
-              // We found a path that exits the loop early, and is not the exit
-              // related to the induction limit, therefore hoisting checks is
-              // an optimistic assumption.
-              unsafe = true;
-            }
-          }
-
-          if (successor->is_start()) {
-            // We found a path that does one loop iteration without meeting any
-            // check, therefore hoisting checks would be likely to cause
-            // unnecessary deopts.
-            return NOT_HOISTABLE;
-          }
-        }
-
-        next = at(current)->NextDominatedBlock();
-      }
-
-      // If we have no next block we need to backtrack the tree traversal.
-      while (next == NULL) {
-        current = current->dominator();
-        if (current != NULL) {
-          next = at(current)->NextDominatedBlock();
-        } else {
-          // We reached the root: next stays NULL.
-          next = NULL;
-          break;
-        }
-      }
-
-      current = next;
-    }
-
-    return unsafe ? OPTIMISTICALLY_HOISTABLE : HOISTABLE;
-  }
-
-  explicit InductionVariableBlocksTable(HGraph* graph)
-    : graph_(graph), loop_header_(NULL),
-      elements_(graph->blocks()->length(), graph->zone()) {
-    for (int i = 0; i < graph->blocks()->length(); i++) {
-      Element element;
-      element.set_block(graph->blocks()->at(i));
-      elements_.Add(element, graph->zone());
-      DCHECK(at(i)->block()->block_id() == i);
-    }
-  }
-
-  // Tries to hoist a check out of its induction loop.
-  void ProcessRelatedChecks(
-      InductionVariableData::InductionVariableCheck* check,
-      InductionVariableData* data) {
-    HValue* length = check->check()->length();
-    check->set_processed();
-    HBasicBlock* header =
-        data->phi()->block()->current_loop()->loop_header();
-    HBasicBlock* pre_header = header->predecessors()->at(0);
-    // Check that the limit is defined in the loop preheader.
-    if (!data->limit()->IsInteger32Constant()) {
-      HBasicBlock* limit_block = data->limit()->block();
-      if (limit_block != pre_header &&
-          !limit_block->Dominates(pre_header)) {
-        return;
-      }
-    }
-    // Check that the length and limit have compatible representations.
-    if (!(data->limit()->representation().Equals(
-            length->representation()) ||
-        data->limit()->IsInteger32Constant())) {
-      return;
-    }
-    // Check that the length is defined in the loop preheader.
-    if (check->check()->length()->block() != pre_header &&
-        !check->check()->length()->block()->Dominates(pre_header)) {
-      return;
-    }
-
-    // Add checks to the table.
-    for (InductionVariableData::InductionVariableCheck* current_check = check;
-         current_check != NULL;
-         current_check = current_check->next()) {
-      if (current_check->check()->length() != length) continue;
-
-      AddCheckAt(current_check->check()->block());
-      current_check->set_processed();
-    }
-
-    // Check that we will not cause unwanted deoptimizations.
-    Hoistability hoistability = CheckHoistability();
-    if (hoistability == NOT_HOISTABLE ||
-        (hoistability == OPTIMISTICALLY_HOISTABLE &&
-         !graph()->use_optimistic_licm())) {
-      return;
-    }
-
-    // We will do the hoisting, but we must see if the limit is "limit" or if
-    // all checks are done on constants: if all check are done against the same
-    // constant limit we will use that instead of the induction limit.
-    bool has_upper_constant_limit = true;
-    int32_t upper_constant_limit =
-        check->HasUpperLimit() ? check->upper_limit() : 0;
-    for (InductionVariableData::InductionVariableCheck* current_check = check;
-         current_check != NULL;
-         current_check = current_check->next()) {
-      has_upper_constant_limit =
-          has_upper_constant_limit && current_check->HasUpperLimit() &&
-          current_check->upper_limit() == upper_constant_limit;
-      counters()->bounds_checks_eliminated()->Increment();
-      current_check->check()->set_skip_check();
-    }
-
-    // Choose the appropriate limit.
-    Zone* zone = graph()->zone();
-    HValue* context = graph()->GetInvalidContext();
-    HValue* limit = data->limit();
-    if (has_upper_constant_limit) {
-      HConstant* new_limit = HConstant::New(graph()->isolate(), zone, context,
-                                            upper_constant_limit);
-      new_limit->InsertBefore(pre_header->end());
-      limit = new_limit;
-    }
-
-    // If necessary, redefine the limit in the preheader.
-    if (limit->IsInteger32Constant() &&
-        limit->block() != pre_header &&
-        !limit->block()->Dominates(pre_header)) {
-      HConstant* new_limit = HConstant::New(graph()->isolate(), zone, context,
-                                            limit->GetInteger32Constant());
-      new_limit->InsertBefore(pre_header->end());
-      limit = new_limit;
-    }
-
-    // Do the hoisting.
-    HBoundsCheck* hoisted_check = HBoundsCheck::New(
-        graph()->isolate(), zone, context, limit, check->check()->length());
-    hoisted_check->InsertBefore(pre_header->end());
-    hoisted_check->set_allow_equality(true);
-    counters()->bounds_checks_hoisted()->Increment();
-  }
-
-  void CollectInductionVariableData(HBasicBlock* bb) {
-    bool additional_limit = false;
-
-    for (int i = 0; i < bb->phis()->length(); i++) {
-      HPhi* phi = bb->phis()->at(i);
-      phi->DetectInductionVariable();
-    }
-
-    additional_limit = InductionVariableData::ComputeInductionVariableLimit(
-        bb, at(bb)->additional_limit());
-
-    if (additional_limit) {
-      at(bb)->additional_limit()->updated_variable->
-          UpdateAdditionalLimit(at(bb)->additional_limit());
-    }
-
-    for (HInstruction* i = bb->first(); i != NULL; i = i->next()) {
-      if (!i->IsBoundsCheck()) continue;
-      HBoundsCheck* check = HBoundsCheck::cast(i);
-      InductionVariableData::BitwiseDecompositionResult decomposition;
-      InductionVariableData::DecomposeBitwise(check->index(), &decomposition);
-      if (!decomposition.base->IsPhi()) continue;
-      HPhi* phi = HPhi::cast(decomposition.base);
-
-      if (!phi->IsInductionVariable()) continue;
-      InductionVariableData* data = phi->induction_variable_data();
-
-      // For now ignore loops decrementing the index.
-      if (data->increment() <= 0) continue;
-      if (!data->LowerLimitIsNonNegativeConstant()) continue;
-
-      // TODO(mmassi): skip OSR values for check->length().
-      if (check->length() == data->limit() ||
-          check->length() == data->additional_upper_limit()) {
-        counters()->bounds_checks_eliminated()->Increment();
-        check->set_skip_check();
-        continue;
-      }
-
-      if (!phi->IsLimitedInductionVariable()) continue;
-
-      int32_t limit = data->ComputeUpperLimit(decomposition.and_mask,
-                                              decomposition.or_mask);
-      phi->induction_variable_data()->AddCheck(check, limit);
-    }
-
-    for (int i = 0; i < bb->dominated_blocks()->length(); i++) {
-      CollectInductionVariableData(bb->dominated_blocks()->at(i));
-    }
-
-    if (additional_limit) {
-      at(bb->block_id())->additional_limit()->updated_variable->
-          UpdateAdditionalLimit(at(bb->block_id())->additional_limit());
-    }
-  }
-
-  void EliminateRedundantBoundsChecks(HBasicBlock* bb) {
-    for (int i = 0; i < bb->phis()->length(); i++) {
-      HPhi* phi = bb->phis()->at(i);
-      if (!phi->IsLimitedInductionVariable()) continue;
-
-      InductionVariableData* induction_data = phi->induction_variable_data();
-      InductionVariableData::ChecksRelatedToLength* current_length_group =
-          induction_data->checks();
-      while (current_length_group != NULL) {
-        current_length_group->CloseCurrentBlock();
-        InductionVariableData::InductionVariableCheck* current_base_check =
-            current_length_group->checks();
-        InitializeLoop(induction_data);
-
-        while (current_base_check != NULL) {
-          ProcessRelatedChecks(current_base_check, induction_data);
-          while (current_base_check != NULL &&
-                 current_base_check->processed()) {
-            current_base_check = current_base_check->next();
-          }
-        }
-
-        current_length_group = current_length_group->next();
-      }
-    }
-  }
-
- private:
-  HGraph* graph_;
-  HBasicBlock* loop_header_;
-  ZoneList<Element> elements_;
-};
-
-
-void HBoundsCheckHoistingPhase::HoistRedundantBoundsChecks() {
-  InductionVariableBlocksTable table(graph());
-  table.CollectInductionVariableData(graph()->entry_block());
-  for (int i = 0; i < graph()->blocks()->length(); i++) {
-    table.EliminateRedundantBoundsChecks(graph()->blocks()->at(i));
-  }
-}
-
-}  // namespace internal
-}  // namespace v8