diff options
Diffstat (limited to 'absl/base/internal/unaligned_access.h')
| -rw-r--r-- | absl/base/internal/unaligned_access.h | 181 |
1 files changed, 5 insertions, 176 deletions
diff --git a/absl/base/internal/unaligned_access.h b/absl/base/internal/unaligned_access.h index 07a64bba..a709a446 100644 --- a/absl/base/internal/unaligned_access.h +++ b/absl/base/internal/unaligned_access.h @@ -5,7 +5,7 @@ // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // -// http://www.apache.org/licenses/LICENSE-2.0 +// https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, @@ -25,15 +25,6 @@ // unaligned APIs // Portable handling of unaligned loads, stores, and copies. -// On some platforms, like ARM, the copy functions can be more efficient -// then a load and a store. -// -// It is possible to implement all of these these using constant-length memcpy -// calls, which is portable and will usually be inlined into simple loads and -// stores if the architecture supports it. However, such inlining usually -// happens in a pass that's quite late in compilation, which means the resulting -// loads and stores cannot participate in many other optimizations, leading to -// overall worse code. // The unaligned API is C++ only. The declarations use C++ features // (namespaces, inline) which are absent or incompatible in C. @@ -65,7 +56,7 @@ void __sanitizer_unaligned_store64(void *p, uint64_t v); } // extern "C" namespace absl { -inline namespace lts_2018_12_18 { +inline namespace lts_2019_08_08 { namespace base_internal { inline uint16_t UnalignedLoad16(const void *p) { @@ -93,7 +84,7 @@ inline void UnalignedStore64(void *p, uint64_t v) { } } // namespace base_internal -} // inline namespace lts_2018_12_18 +} // inline namespace lts_2019_08_08 } // namespace absl #define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \ @@ -110,172 +101,10 @@ inline void UnalignedStore64(void *p, uint64_t v) { #define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \ (absl::base_internal::UnalignedStore64(_p, _val)) -#elif defined(UNDEFINED_BEHAVIOR_SANITIZER) - -namespace absl { -inline namespace lts_2018_12_18 { -namespace base_internal { - -inline uint16_t UnalignedLoad16(const void *p) { - uint16_t t; - memcpy(&t, p, sizeof t); - return t; -} - -inline uint32_t UnalignedLoad32(const void *p) { - uint32_t t; - memcpy(&t, p, sizeof t); - return t; -} - -inline uint64_t UnalignedLoad64(const void *p) { - uint64_t t; - memcpy(&t, p, sizeof t); - return t; -} - -inline void UnalignedStore16(void *p, uint16_t v) { memcpy(p, &v, sizeof v); } - -inline void UnalignedStore32(void *p, uint32_t v) { memcpy(p, &v, sizeof v); } - -inline void UnalignedStore64(void *p, uint64_t v) { memcpy(p, &v, sizeof v); } - -} // namespace base_internal -} // inline namespace lts_2018_12_18 -} // namespace absl - -#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \ - (absl::base_internal::UnalignedLoad16(_p)) -#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \ - (absl::base_internal::UnalignedLoad32(_p)) -#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \ - (absl::base_internal::UnalignedLoad64(_p)) - -#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \ - (absl::base_internal::UnalignedStore16(_p, _val)) -#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \ - (absl::base_internal::UnalignedStore32(_p, _val)) -#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \ - (absl::base_internal::UnalignedStore64(_p, _val)) - -#elif defined(__x86_64__) || defined(_M_X64) || defined(__i386) || \ - defined(_M_IX86) || defined(__ppc__) || defined(__PPC__) || \ - defined(__ppc64__) || defined(__PPC64__) - -// x86 and x86-64 can perform unaligned loads/stores directly; -// modern PowerPC hardware can also do unaligned integer loads and stores; -// but note: the FPU still sends unaligned loads and stores to a trap handler! - -#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \ - (*reinterpret_cast<const uint16_t *>(_p)) -#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \ - (*reinterpret_cast<const uint32_t *>(_p)) -#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \ - (*reinterpret_cast<const uint64_t *>(_p)) - -#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \ - (*reinterpret_cast<uint16_t *>(_p) = (_val)) -#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \ - (*reinterpret_cast<uint32_t *>(_p) = (_val)) -#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \ - (*reinterpret_cast<uint64_t *>(_p) = (_val)) - -#elif defined(__arm__) && \ - !defined(__ARM_ARCH_5__) && \ - !defined(__ARM_ARCH_5T__) && \ - !defined(__ARM_ARCH_5TE__) && \ - !defined(__ARM_ARCH_5TEJ__) && \ - !defined(__ARM_ARCH_6__) && \ - !defined(__ARM_ARCH_6J__) && \ - !defined(__ARM_ARCH_6K__) && \ - !defined(__ARM_ARCH_6Z__) && \ - !defined(__ARM_ARCH_6ZK__) && \ - !defined(__ARM_ARCH_6T2__) - - -// ARMv7 and newer support native unaligned accesses, but only of 16-bit -// and 32-bit values (not 64-bit); older versions either raise a fatal signal, -// do an unaligned read and rotate the words around a bit, or do the reads very -// slowly (trip through kernel mode). There's no simple #define that says just -// "ARMv7 or higher", so we have to filter away all ARMv5 and ARMv6 -// sub-architectures. Newer gcc (>= 4.6) set an __ARM_FEATURE_ALIGNED #define, -// so in time, maybe we can move on to that. -// -// This is a mess, but there's not much we can do about it. -// -// To further complicate matters, only LDR instructions (single reads) are -// allowed to be unaligned, not LDRD (two reads) or LDM (many reads). Unless we -// explicitly tell the compiler that these accesses can be unaligned, it can and -// will combine accesses. On armcc, the way to signal this is done by accessing -// through the type (uint32_t __packed *), but GCC has no such attribute -// (it ignores __attribute__((packed)) on individual variables). However, -// we can tell it that a _struct_ is unaligned, which has the same effect, -// so we do that. - -namespace absl { -inline namespace lts_2018_12_18 { -namespace base_internal { - -struct Unaligned16Struct { - uint16_t value; - uint8_t dummy; // To make the size non-power-of-two. -} ABSL_ATTRIBUTE_PACKED; - -struct Unaligned32Struct { - uint32_t value; - uint8_t dummy; // To make the size non-power-of-two. -} ABSL_ATTRIBUTE_PACKED; - -} // namespace base_internal -} // inline namespace lts_2018_12_18 -} // namespace absl - -#define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \ - ((reinterpret_cast<const ::absl::base_internal::Unaligned16Struct *>(_p)) \ - ->value) -#define ABSL_INTERNAL_UNALIGNED_LOAD32(_p) \ - ((reinterpret_cast<const ::absl::base_internal::Unaligned32Struct *>(_p)) \ - ->value) - -#define ABSL_INTERNAL_UNALIGNED_STORE16(_p, _val) \ - ((reinterpret_cast< ::absl::base_internal::Unaligned16Struct *>(_p)) \ - ->value = (_val)) -#define ABSL_INTERNAL_UNALIGNED_STORE32(_p, _val) \ - ((reinterpret_cast< ::absl::base_internal::Unaligned32Struct *>(_p)) \ - ->value = (_val)) - -namespace absl { -inline namespace lts_2018_12_18 { -namespace base_internal { - -inline uint64_t UnalignedLoad64(const void *p) { - uint64_t t; - memcpy(&t, p, sizeof t); - return t; -} - -inline void UnalignedStore64(void *p, uint64_t v) { memcpy(p, &v, sizeof v); } - -} // namespace base_internal -} // inline namespace lts_2018_12_18 -} // namespace absl - -#define ABSL_INTERNAL_UNALIGNED_LOAD64(_p) \ - (absl::base_internal::UnalignedLoad64(_p)) -#define ABSL_INTERNAL_UNALIGNED_STORE64(_p, _val) \ - (absl::base_internal::UnalignedStore64(_p, _val)) - #else -// ABSL_INTERNAL_NEED_ALIGNED_LOADS is defined when the underlying platform -// doesn't support unaligned access. -#define ABSL_INTERNAL_NEED_ALIGNED_LOADS - -// These functions are provided for architectures that don't support -// unaligned loads and stores. - namespace absl { -inline namespace lts_2018_12_18 { +inline namespace lts_2019_08_08 { namespace base_internal { inline uint16_t UnalignedLoad16(const void *p) { @@ -303,7 +132,7 @@ inline void UnalignedStore32(void *p, uint32_t v) { memcpy(p, &v, sizeof v); } inline void UnalignedStore64(void *p, uint64_t v) { memcpy(p, &v, sizeof v); } } // namespace base_internal -} // inline namespace lts_2018_12_18 +} // inline namespace lts_2019_08_08 } // namespace absl #define ABSL_INTERNAL_UNALIGNED_LOAD16(_p) \ |