6241875073
Adds support for double-word aligned, i.e., 8 bytes on 32-bit platforms and 16 bytes on 64-bit platforms, objects in Oilpan. Changes: - Adds generic alignment APIs and overrides. - Internal logic to support double-word aligned allocations on LABs. - Adjusts natural alignment of large objects to follow double-word. - Adds a new static_assert() that suggests users file a bug if higher alignment is required. - Statically checks that no allocations with non-default alignment target custom spaces that support compaction. Bug: v8:12295 Change-Id: I05766ce2349055d5d78b68919be00e7ee91d5505 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3218150 Reviewed-by: Anton Bikineev <bikineev@chromium.org> Commit-Queue: Michael Lippautz <mlippautz@chromium.org> Cr-Commit-Position: refs/heads/main@{#77348}
56 lines
1.8 KiB
C++
56 lines
1.8 KiB
C++
// Copyright 2020 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_
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#define INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_
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#include <cstddef>
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#include <cstdint>
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#include "v8config.h" // NOLINT(build/include_directory)
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namespace cppgc {
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namespace internal {
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// Embedders should not rely on this code!
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// Internal constants to avoid exposing internal types on the API surface.
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namespace api_constants {
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constexpr size_t kKB = 1024;
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constexpr size_t kMB = kKB * 1024;
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constexpr size_t kGB = kMB * 1024;
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// Offset of the uint16_t bitfield from the payload contaning the
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// in-construction bit. This is subtracted from the payload pointer to get
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// to the right bitfield.
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static constexpr size_t kFullyConstructedBitFieldOffsetFromPayload =
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2 * sizeof(uint16_t);
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// Mask for in-construction bit.
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static constexpr uint16_t kFullyConstructedBitMask = uint16_t{1};
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static constexpr size_t kPageSize = size_t{1} << 17;
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static constexpr size_t kLargeObjectSizeThreshold = kPageSize / 2;
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#if defined(CPPGC_CAGED_HEAP)
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constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(4) * kGB;
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constexpr size_t kCagedHeapReservationAlignment = kCagedHeapReservationSize;
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#endif
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static constexpr size_t kDefaultAlignment = sizeof(void*);
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// Maximum support alignment for a type as in `alignof(T)`.
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static constexpr size_t kMaxSupportedAlignment = 2 * kDefaultAlignment;
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static_assert(kMaxSupportedAlignment >= alignof(std::max_align_t),
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"Maximum support alignment must at least cover "
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"alignof(std::max_align_t).");
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} // namespace api_constants
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} // namespace internal
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} // namespace cppgc
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#endif // INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_
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