LLVM 20.0.0git
SipHash.h
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1//===--- SipHash.h - An ABI-stable string SipHash ---------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// An implementation of SipHash, a hash function optimized for speed on
10// short inputs. Based on the SipHash reference implementation.
11//
12// Also provides one specific wrapper on top of SipHash-2-4-64 to compute
13// compute ABI-stable ptrauth discriminators.
14//
15//===----------------------------------------------------------------------===//
16
17#ifndef LLVM_SUPPORT_SIPHASH_H
18#define LLVM_SUPPORT_SIPHASH_H
19
20#include <cstdint>
21
22namespace llvm {
23
24template <typename T> class ArrayRef;
25class StringRef;
26
27/// Computes a SipHash-2-4 64-bit result.
28void getSipHash_2_4_64(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
29 uint8_t (&Out)[8]);
30
31/// Computes a SipHash-2-4 128-bit result.
32void getSipHash_2_4_128(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
33 uint8_t (&Out)[16]);
34
35/// Compute a stable non-zero 16-bit hash of the given string.
36///
37/// The exact algorithm is the little-endian interpretation of the
38/// non-doubled (i.e. 64-bit) result of applying a SipHash-2-4 using
39/// a specific seed value which can be found in the source.
40/// This 64-bit result is truncated to a non-zero 16-bit value.
41///
42/// We use a 16-bit discriminator because ARM64 can efficiently load
43/// a 16-bit immediate into the high bits of a register without disturbing
44/// the remainder of the value, which serves as a nice blend operation.
45/// 16 bits is also sufficiently compact to not inflate a loader relocation.
46/// We disallow zero to guarantee a different discriminator from the places
47/// in the ABI that use a constant zero.
49
50} // end namespace llvm
51
52#endif
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
void getSipHash_2_4_64(ArrayRef< uint8_t > In, const uint8_t(&K)[16], uint8_t(&Out)[8])
Computes a SipHash-2-4 64-bit result.
Definition: SipHash.cpp:157
uint16_t getPointerAuthStableSipHash(StringRef S)
Compute a stable non-zero 16-bit hash of the given string.
Definition: SipHash.cpp:168
ArrayRef(const T &OneElt) -> ArrayRef< T >
void getSipHash_2_4_128(ArrayRef< uint8_t > In, const uint8_t(&K)[16], uint8_t(&Out)[16])
Computes a SipHash-2-4 128-bit result.
Definition: SipHash.cpp:162