================ @@ -0,0 +1,47 @@ +//===--- SipHash.h - An ABI-stable string SipHash ---------------*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// A family of ABI-stable string hash algorithms based on SipHash, currently +// used to compute ptrauth discriminators. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_SUPPORT_SIPHASH_H +#define LLVM_SUPPORT_SIPHASH_H + +#include <cstdint> + +namespace llvm { +class StringRef; + +/// Compute a stable 64-bit hash of the given string. +/// +/// The exact algorithm is the little-endian interpretation of the +/// non-doubled (i.e. 64-bit) result of applying a SipHash-2-4 using +/// a specific key value which can be found in the source. +/// +/// By "stable" we mean that the result of this hash algorithm will +/// the same across different compiler versions and target platforms. +uint64_t getPointerAuthStableSipHash64(StringRef S); + +/// Compute a stable non-zero 16-bit hash of the given string. +/// +/// This computes the full getPointerAuthStableSipHash64, but additionally +/// truncates it down to a non-zero 16-bit value. +/// +/// We use a 16-bit discriminator because ARM64 can efficiently load +/// a 16-bit immediate into the high bits of a register without disturbing +/// the remainder of the value, which serves as a nice blend operation. +/// 16 bits is also sufficiently compact to not inflate a loader relocation. +/// We disallow zero to guarantee a different discriminator from the places +/// in the ABI that use a constant zero. +uint64_t getPointerAuthStableSipHash16(StringRef S); ---------------- kovdan01 wrote:
Is having `uint64_t` as return value type intentional even for a function which by design always returns a 16-bit value? https://github.com/llvm/llvm-project/pull/93902 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
