================ @@ -0,0 +1,222 @@ +//===--- ProfileFuncRef.h - Sample profile function name ---*- 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 +// +//===----------------------------------------------------------------------===// +// +// This file defines the StringRefOrHashCode class. It is to represent function +// names in a sample profile, which can be in one of two forms - either a +// regular string, or a 64-bit hash code. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_PROFILEDATA_PROFILEFUNCREF_H +#define LLVM_PROFILEDATA_PROFILEFUNCREF_H + +#include "llvm/ADT/DenseMapInfo.h" +#include "llvm/ADT/Hashing.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/Support/MD5.h" +#include "llvm/Support/raw_ostream.h" +#include <cstdint> + +namespace llvm { +namespace sampleprof { + +/// This class represents a function name that is read from a sample profile. It +/// comes with two forms: a string or a hash code. For efficient storage, a +/// sample profile may store function names as 64-bit MD5 values, so when +/// reading the profile, this class can represnet them without converting it to +/// a string first. +/// When representing a hash code, we utilize the Length field to store it, and +/// Data is set to null. When representing a string, it is same as StringRef, +/// and can be pointer-casted as one. +/// We disallow implicit cast to StringRef because there are too many instances +/// that it may cause break the code, such as using it in a StringMap. +class ProfileFuncRef { + + const char *Data = nullptr; + + /// Use uint64_t instead of size_t so that it can also hold a MD5 value. + uint64_t LengthOrHashCode = 0; + + /// Extension to memcmp to handle hash code representation. If both are hash + /// values, Lhs and Rhs are both null, function returns 0 (and needs an extra + /// comparison using getIntValue). If only one is hash code, it is considered + /// less than the StringRef one. Otherwise perform normal string comparison. + static int compareMemory(const char *Lhs, const char *Rhs, uint64_t Length) { ---------------- huangjd wrote:
When both objects are MD5 values, the full uint64_t field must be compared, and converting it to size_t by the caller will truncate the hash on 32-bit system. Meanwhile the conversion at memcmp is ok because at that point we already deduce that both objects are StringRef, which can only have size_t as length. https://github.com/llvm/llvm-project/pull/66164 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
