| // Copyright 2014 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/compiler/value-numbering-reducer.h" |
| |
| #include <cstring> |
| |
| #include "src/base/functional.h" |
| #include "src/compiler/node-properties.h" |
| #include "src/compiler/node.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| ValueNumberingReducer::ValueNumberingReducer(Zone* temp_zone, Zone* graph_zone) |
| : entries_(nullptr), |
| capacity_(0), |
| size_(0), |
| temp_zone_(temp_zone), |
| graph_zone_(graph_zone) {} |
| |
| ValueNumberingReducer::~ValueNumberingReducer() {} |
| |
| |
| Reduction ValueNumberingReducer::Reduce(Node* node) { |
| if (!node->op()->HasProperty(Operator::kIdempotent)) return NoChange(); |
| |
| const size_t hash = NodeProperties::HashCode(node); |
| if (!entries_) { |
| DCHECK_EQ(0, size_); |
| DCHECK_EQ(0, capacity_); |
| // Allocate the initial entries and insert the first entry. |
| capacity_ = kInitialCapacity; |
| entries_ = temp_zone()->NewArray<Node*>(kInitialCapacity); |
| memset(entries_, 0, sizeof(*entries_) * kInitialCapacity); |
| entries_[hash & (kInitialCapacity - 1)] = node; |
| size_ = 1; |
| return NoChange(); |
| } |
| |
| DCHECK(size_ < capacity_); |
| DCHECK(size_ + size_ / 4 < capacity_); |
| |
| const size_t mask = capacity_ - 1; |
| size_t dead = capacity_; |
| |
| for (size_t i = hash & mask;; i = (i + 1) & mask) { |
| Node* entry = entries_[i]; |
| if (!entry) { |
| if (dead != capacity_) { |
| // Reuse dead entry that we discovered on the way. |
| entries_[dead] = node; |
| } else { |
| // Have to insert a new entry. |
| entries_[i] = node; |
| size_++; |
| |
| // Resize to keep load factor below 80% |
| if (size_ + size_ / 4 >= capacity_) Grow(); |
| } |
| DCHECK(size_ + size_ / 4 < capacity_); |
| return NoChange(); |
| } |
| |
| if (entry == node) { |
| // We need to check for a certain class of collisions here. Imagine the |
| // following scenario: |
| // |
| // 1. We insert node1 with op1 and certain inputs at index i. |
| // 2. We insert node2 with op2 and certain inputs at index i+1. |
| // 3. Some other reducer changes node1 to op2 and the inputs from node2. |
| // |
| // Now we are called again to reduce node1, and we would return NoChange |
| // in this case because we find node1 first, but what we should actually |
| // do is return Replace(node2) instead. |
| for (size_t j = (i + 1) & mask;; j = (j + 1) & mask) { |
| Node* entry = entries_[j]; |
| if (!entry) { |
| // No collision, {node} is fine. |
| return NoChange(); |
| } |
| if (entry->IsDead()) { |
| continue; |
| } |
| if (entry == node) { |
| // Collision with ourselves, doesn't count as a real collision. |
| // Opportunistically clean-up the duplicate entry if we're at the end |
| // of a bucket. |
| if (!entries_[(j + 1) & mask]) { |
| entries_[j] = nullptr; |
| size_--; |
| return NoChange(); |
| } |
| // Otherwise, keep searching for another collision. |
| continue; |
| } |
| if (NodeProperties::Equals(entry, node)) { |
| Reduction reduction = ReplaceIfTypesMatch(node, entry); |
| if (reduction.Changed()) { |
| // Overwrite the colliding entry with the actual entry. |
| entries_[i] = entry; |
| // Opportunistically clean-up the duplicate entry if we're at the |
| // end of a bucket. |
| if (!entries_[(j + 1) & mask]) { |
| entries_[j] = nullptr; |
| size_--; |
| } |
| } |
| return reduction; |
| } |
| } |
| } |
| |
| // Skip dead entries, but remember their indices so we can reuse them. |
| if (entry->IsDead()) { |
| dead = i; |
| continue; |
| } |
| if (NodeProperties::Equals(entry, node)) { |
| return ReplaceIfTypesMatch(node, entry); |
| } |
| } |
| } |
| |
| Reduction ValueNumberingReducer::ReplaceIfTypesMatch(Node* node, |
| Node* replacement) { |
| // Make sure the replacement has at least as good type as the original node. |
| if (NodeProperties::IsTyped(replacement) && NodeProperties::IsTyped(node)) { |
| Type* replacement_type = NodeProperties::GetType(replacement); |
| Type* node_type = NodeProperties::GetType(node); |
| if (!replacement_type->Is(node_type)) { |
| // Ideally, we would set an intersection of {replacement_type} and |
| // {node_type} here. However, typing of NumberConstants assigns different |
| // types to constants with the same value (it creates a fresh heap |
| // number), which would make the intersection empty. To be safe, we use |
| // the smaller type if the types are comparable. |
| if (node_type->Is(replacement_type)) { |
| NodeProperties::SetType(replacement, node_type); |
| } else { |
| // Types are not comparable => do not replace. |
| return NoChange(); |
| } |
| } |
| } |
| return Replace(replacement); |
| } |
| |
| |
| void ValueNumberingReducer::Grow() { |
| // Allocate a new block of entries double the previous capacity. |
| Node** const old_entries = entries_; |
| size_t const old_capacity = capacity_; |
| capacity_ *= 2; |
| entries_ = temp_zone()->NewArray<Node*>(capacity_); |
| memset(entries_, 0, sizeof(*entries_) * capacity_); |
| size_ = 0; |
| size_t const mask = capacity_ - 1; |
| |
| // Insert the old entries into the new block (skipping dead nodes). |
| for (size_t i = 0; i < old_capacity; ++i) { |
| Node* const old_entry = old_entries[i]; |
| if (!old_entry || old_entry->IsDead()) continue; |
| for (size_t j = NodeProperties::HashCode(old_entry) & mask;; |
| j = (j + 1) & mask) { |
| Node* const entry = entries_[j]; |
| if (entry == old_entry) { |
| // Skip duplicate of the old entry. |
| break; |
| } |
| if (!entry) { |
| entries_[j] = old_entry; |
| size_++; |
| break; |
| } |
| } |
| } |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |