Ryan Macnak
e991ffd37b
TEST=ubsan Bug: https://github.com/dart-lang/sdk/issues/63452 Change-Id: I112b26c08b5ae186dc5264d99edbed9e6e60368d Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/506660 Reviewed-by: Alexander Aprelev <aam@google.com> Commit-Queue: Ryan Macnak <rmacnak@google.com>
57 lines
1.8 KiB
C++
57 lines
1.8 KiB
C++
// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#ifndef RUNTIME_VM_HASH_H_
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#define RUNTIME_VM_HASH_H_
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#include "platform/globals.h"
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#include "platform/unaligned.h"
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namespace dart {
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inline uint32_t CombineHashes(uint32_t hash, uint32_t other_hash) {
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// Keep in sync with AssemblerBase::CombineHashes.
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hash += other_hash;
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hash += hash << 10;
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hash ^= hash >> 6; // Logical shift, unsigned hash.
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return hash;
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}
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inline uint32_t FinalizeHash(uint32_t hash, intptr_t hashbits = kBitsPerInt32) {
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// Keep in sync with AssemblerBase::FinalizeHash.
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hash += hash << 3;
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hash ^= hash >> 11; // Logical shift, unsigned hash.
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hash += hash << 15;
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if (hashbits < kBitsPerInt32) {
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hash &= (static_cast<uint32_t>(1) << hashbits) - 1;
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}
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return (hash == 0) ? 1 : hash;
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}
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// The value returned by HashBytes when the length is 0. Used to avoid storing
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// canonical hashes to and loading from the heap for empty container Instances.
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static constexpr uint32_t kEmptyContainerHash = 1;
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inline uint32_t HashBytes(const void* bytes,
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intptr_t len,
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intptr_t hashbits = kBitsPerInt32) {
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if (len == 0) {
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return kEmptyContainerHash;
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}
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uint32_t hash = len;
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const intptr_t chunks = len / kInt32Size;
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for (intptr_t i = 0; i < chunks; i++) {
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hash = CombineHashes(
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hash, LoadUnaligned(&(reinterpret_cast<const uint32_t*>(bytes)[i])));
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}
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for (intptr_t i = chunks * kInt32Size; i < len; i++) {
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hash = CombineHashes(hash, reinterpret_cast<const uint8_t*>(bytes)[i]);
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}
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return FinalizeHash(hash, hashbits);
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}
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} // namespace dart
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#endif // RUNTIME_VM_HASH_H_
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