| //===-- Memory utils --------------------------------------------*- 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 |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_LIBC_SRC_MEMORY_UTILS_UTILS_H |
| #define LLVM_LIBC_SRC_MEMORY_UTILS_UTILS_H |
| |
| #include "src/__support/architectures.h" |
| |
| // Cache line sizes for ARM: These values are not strictly correct since |
| // cache line sizes depend on implementations, not architectures. There |
| // are even implementations with cache line sizes configurable at boot |
| // time. |
| #if defined(LLVM_LIBC_ARCH_AARCH64) || defined(LLVM_LIBC_ARCH_X86) |
| #define LLVM_LIBC_CACHELINE_SIZE 64 |
| #else |
| #error "Unsupported platform for memory functions." |
| #endif |
| |
| #include <stddef.h> // size_t |
| #include <stdint.h> // intptr_t / uintptr_t |
| |
| namespace __llvm_libc { |
| |
| // Return whether `value` is zero or a power of two. |
| static constexpr bool is_power2_or_zero(size_t value) { |
| return (value & (value - 1U)) == 0; |
| } |
| |
| // Return whether `value` is a power of two. |
| static constexpr bool is_power2(size_t value) { |
| return value && is_power2_or_zero(value); |
| } |
| |
| // Compile time version of log2 that handles 0. |
| static constexpr size_t log2(size_t value) { |
| return (value == 0 || value == 1) ? 0 : 1 + log2(value / 2); |
| } |
| |
| // Returns the first power of two preceding value or value if it is already a |
| // power of two (or 0 when value is 0). |
| static constexpr size_t le_power2(size_t value) { |
| return value == 0 ? value : 1ULL << log2(value); |
| } |
| |
| // Returns the first power of two following value or value if it is already a |
| // power of two (or 0 when value is 0). |
| static constexpr size_t ge_power2(size_t value) { |
| return is_power2_or_zero(value) ? value : 1ULL << (log2(value) + 1); |
| } |
| |
| template <size_t alignment> intptr_t offset_from_last_aligned(const void *ptr) { |
| static_assert(is_power2(alignment), "alignment must be a power of 2"); |
| return reinterpret_cast<uintptr_t>(ptr) & (alignment - 1U); |
| } |
| |
| template <size_t alignment> intptr_t offset_to_next_aligned(const void *ptr) { |
| static_assert(is_power2(alignment), "alignment must be a power of 2"); |
| // The logic is not straightforward and involves unsigned modulo arithmetic |
| // but the generated code is as fast as it can be. |
| return -reinterpret_cast<uintptr_t>(ptr) & (alignment - 1U); |
| } |
| |
| // Returns the offset from `ptr` to the next cache line. |
| static inline intptr_t offset_to_next_cache_line(const void *ptr) { |
| return offset_to_next_aligned<LLVM_LIBC_CACHELINE_SIZE>(ptr); |
| } |
| |
| template <size_t alignment, typename T> static T *assume_aligned(T *ptr) { |
| return reinterpret_cast<T *>(__builtin_assume_aligned(ptr, alignment)); |
| } |
| |
| } // namespace __llvm_libc |
| |
| #endif // LLVM_LIBC_SRC_MEMORY_UTILS_UTILS_H |