| // 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.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| namespace { |
| |
| size_t HashCode(Node* node) { |
| size_t h = base::hash_combine(node->op()->HashCode(), node->InputCount()); |
| for (int j = 0; j < node->InputCount(); ++j) { |
| h = base::hash_combine(h, node->InputAt(j)->id()); |
| } |
| return h; |
| } |
| |
| |
| bool Equals(Node* a, Node* b) { |
| DCHECK_NOT_NULL(a); |
| DCHECK_NOT_NULL(b); |
| DCHECK_NOT_NULL(a->op()); |
| DCHECK_NOT_NULL(b->op()); |
| if (!a->op()->Equals(b->op())) return false; |
| if (a->InputCount() != b->InputCount()) return false; |
| for (int j = 0; j < a->InputCount(); ++j) { |
| DCHECK_NOT_NULL(a->InputAt(j)); |
| DCHECK_NOT_NULL(b->InputAt(j)); |
| if (a->InputAt(j)->id() != b->InputAt(j)->id()) return false; |
| } |
| return true; |
| } |
| |
| } // namespace |
| |
| |
| ValueNumberingReducer::ValueNumberingReducer(Zone* zone) |
| : entries_(nullptr), capacity_(0), size_(0), zone_(zone) {} |
| |
| |
| ValueNumberingReducer::~ValueNumberingReducer() {} |
| |
| |
| Reduction ValueNumberingReducer::Reduce(Node* node) { |
| if (!node->op()->HasProperty(Operator::kEliminatable)) return NoChange(); |
| |
| const size_t hash = HashCode(node); |
| if (!entries_) { |
| DCHECK(size_ == 0); |
| DCHECK(capacity_ == 0); |
| // Allocate the initial entries and insert the first entry. |
| capacity_ = kInitialCapacity; |
| entries_ = zone()->NewArray<Node*>(kInitialCapacity); |
| memset(entries_, 0, sizeof(*entries_) * kInitialCapacity); |
| entries_[hash & (kInitialCapacity - 1)] = node; |
| size_ = 1; |
| return NoChange(); |
| } |
| |
| DCHECK(size_ < capacity_); |
| DCHECK(size_ * kCapacityToSizeRatio < 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 1/kCapacityToSizeRatio. |
| if (size_ * kCapacityToSizeRatio >= capacity_) Grow(); |
| } |
| DCHECK(size_ * kCapacityToSizeRatio < 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 (Equals(entry, node)) { |
| // Overwrite the colliding entry with the actual entry. |
| entries_[i] = entry; |
| return Replace(entry); |
| } |
| } |
| } |
| |
| // Skip dead entries, but remember their indices so we can reuse them. |
| if (entry->IsDead()) { |
| dead = i; |
| continue; |
| } |
| if (Equals(entry, node)) { |
| return Replace(entry); |
| } |
| } |
| } |
| |
| |
| void ValueNumberingReducer::Grow() { |
| // Allocate a new block of entries kCapacityToSizeRatio times the previous |
| // capacity. |
| Node** const old_entries = entries_; |
| size_t const old_capacity = capacity_; |
| capacity_ *= kCapacityToSizeRatio; |
| entries_ = zone()->NewArray<Node*>(static_cast<int>(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 = 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 |