[turbofan] Reenable value numbering.

src/compiler/value-numbering-reducer.cc

 // 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) { return node->op()->HashCode(); }
+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
 
 
-class ValueNumberingReducer::Entry FINAL : public ZoneObject {
- public:
-  Entry(Node* node, Entry* next) : node_(node), next_(next) {}
-
-  Node* node() const { return node_; }
-  Entry* next() const { return next_; }
-
- private:
-  Node* node_;
-  Entry* next_;
-};
-
-
-ValueNumberingReducer::ValueNumberingReducer(Zone* zone) : zone_(zone) {
-  for (size_t i = 0; i < arraysize(buckets_); ++i) {
-    buckets_[i] = NULL;
-  }
-}
+ValueNumberingReducer::ValueNumberingReducer(Zone* zone)
+    : entries_(nullptr), capacity_(0), size_(0), zone_(zone) {}
 
 
 ValueNumberingReducer::~ValueNumberingReducer() {}
 
 
 Reduction ValueNumberingReducer::Reduce(Node* node) {
-  Entry** head = &buckets_[HashCode(node) % arraysize(buckets_)];
-  for (Entry* entry = *head; entry; entry = entry->next()) {
-    if (entry->node()->IsDead()) continue;
-    if (entry->node() == node) return NoChange();
-    if (Equals(node, entry->node())) {
-      return Replace(entry->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) {
+      return NoChange();
+    }
+
+    // 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);
     }
   }
-  *head = new (zone()) Entry(node, *head);
-  return NoChange();
+}
+
+
+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*>(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 entry = old_entries[i];
+    if (!entry || entry->IsDead()) continue;
+    for (size_t j = HashCode(entry) & mask;; j = (j + 1) & mask) {
+      if (!entries_[j]) {
+        entries_[j] = entry;
+        size_++;
+        break;
+      }
+    }
+  }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8