1 files changed, 71 insertions, 0 deletions
diff --git a/deps/v8/src/heap/base/active-system-pages.cc b/deps/v8/src/heap/base/active-system-pages.cc
new file mode 100644
index 0000000000..8ad225461e
--- /dev/null
+++ b/deps/v8/src/heap/base/active-system-pages.cc
@@ -0,0 +1,71 @@
+// Copyright 2022 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/heap/base/active-system-pages.h"
+
+#include <climits>
+
+#include "src/base/bits.h"
+#include "src/base/macros.h"
+
+namespace heap {
+namespace base {
+
+size_t ActiveSystemPages::Init(size_t header_size, size_t page_size_bits,
+                               size_t user_page_size) {
+#if DEBUG
+  size_t page_size = 1 << page_size_bits;
+  DCHECK_LE(RoundUp(user_page_size, page_size) >> page_size_bits,
+            ActiveSystemPages::kMaxPages);
+#endif  // DEBUG
+  Clear();
+  return Add(0, header_size, page_size_bits);
+}
+
+size_t ActiveSystemPages::Add(uintptr_t start, uintptr_t end,
+                              size_t page_size_bits) {
+  const size_t page_size = 1 << page_size_bits;
+
+  DCHECK_LE(start, end);
+  DCHECK_LE(end, kMaxPages * page_size);
+
+  // Make sure we actually get the bitcount as argument.
+  DCHECK_LT(page_size_bits, sizeof(uintptr_t) * CHAR_BIT);
+
+  const uintptr_t start_page_bit =
+      RoundDown(start, page_size) >> page_size_bits;
+  const uintptr_t end_page_bit = RoundUp(end, page_size) >> page_size_bits;
+  DCHECK_LE(start_page_bit, end_page_bit);
+
+  const uintptr_t bits = end_page_bit - start_page_bit;
+  DCHECK_LE(bits, kMaxPages);
+  const bitset_t mask = bits == kMaxPages
+                            ? int64_t{-1}
+                            : ((uint64_t{1} << bits) - 1) << start_page_bit;
+  const bitset_t added_pages = ~value_ & mask;
+  value_ |= mask;
+  return added_pages.count();
+}
+
+size_t ActiveSystemPages::Reduce(ActiveSystemPages updated_value) {
+  DCHECK_EQ(~value_ & updated_value.value_, 0);
+  const bitset_t removed_pages(value_ & ~updated_value.value_);
+  value_ = updated_value.value_;
+  return removed_pages.count();
+}
+
+size_t ActiveSystemPages::Clear() {
+  const size_t removed_pages = value_.count();
+  value_ = 0;
+  return removed_pages;
+}
+
+size_t ActiveSystemPages::Size(size_t page_size_bits) const {
+  // Make sure we don't get the full page size as argument.
+  DCHECK_LT(page_size_bits, sizeof(uintptr_t) * CHAR_BIT);
+  return value_.count() * (size_t{1} << page_size_bits);
+}
+
+}  // namespace base
+}  // namespace heap