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Diffstat (limited to 'src/cpu-features.h')
| -rw-r--r-- | src/cpu-features.h | 338 |
1 files changed, 338 insertions, 0 deletions
diff --git a/src/cpu-features.h b/src/cpu-features.h new file mode 100644 index 00000000..649e46c3 --- /dev/null +++ b/src/cpu-features.h @@ -0,0 +1,338 @@ +// Copyright 2018, VIXL authors +// All rights reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are met: +// +// * Redistributions of source code must retain the above copyright notice, +// this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above copyright notice, +// this list of conditions and the following disclaimer in the documentation +// and/or other materials provided with the distribution. +// * Neither the name of ARM Limited nor the names of its contributors may be +// used to endorse or promote products derived from this software without +// specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND +// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE +// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE +// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR +// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +#ifndef VIXL_CPU_FEATURES_H +#define VIXL_CPU_FEATURES_H + +#include <ostream> + +#include "globals-vixl.h" + +namespace vixl { + + +// clang-format off +#define VIXL_CPU_FEATURE_LIST(V) \ + /* If set, the OS traps and emulates MRS accesses to relevant (EL1) ID_* */ \ + /* registers, so that the detailed feature registers can be read */ \ + /* directly. */ \ + V(kIDRegisterEmulation, "ID register emulation", "cpuid") \ + \ + V(kFP, "FP", "fp") \ + V(kNEON, "NEON", "asimd") \ + V(kCRC32, "CRC32", "crc32") \ + /* Cryptographic support instructions. */ \ + V(kAES, "AES", "aes") \ + V(kSHA1, "SHA1", "sha1") \ + V(kSHA2, "SHA2", "sha2") \ + /* A form of PMULL{2} with a 128-bit (1Q) result. */ \ + V(kPmull1Q, "Pmull1Q", "pmull") \ + /* Atomic operations on memory: CAS, LDADD, STADD, SWP, etc. */ \ + V(kAtomics, "Atomics", "atomics") \ + /* Limited ordering regions: LDLAR, STLLR and their variants. */ \ + V(kLORegions, "LORegions", NULL) \ + /* Rounding doubling multiply add/subtract: SQRDMLAH and SQRDMLSH. */ \ + V(kRDM, "RDM", "asimdrdm") \ + /* SDOT and UDOT support (in NEON). */ \ + V(kDotProduct, "DotProduct", "asimddp") \ + /* Half-precision (FP16) support for FP and NEON, respectively. */ \ + V(kFPHalf, "FPHalf", "fphp") \ + V(kNEONHalf, "NEONHalf", "asimdhp") \ + /* Data cache clean to the point of persistence: DC CVAP. */ \ + V(kDCPoP, "DCPoP", "dcpop") \ + /* Cryptographic support instructions. */ \ + V(kSHA3, "SHA3", "sha3") \ + V(kSHA512, "SHA512", "sha512") \ + V(kSM3, "SM3", "sm3") \ + V(kSM4, "SM4", "sm4") \ + /* Pointer authentication for addresses. */ \ + V(kPAuth, "PAuth", NULL) \ + /* Pointer authentication for addresses uses QARMA. */ \ + V(kPAuthQARMA, "PAuthQARMA", NULL) \ + /* Generic authentication (using the PACGA instruction). */ \ + V(kPAuthGeneric, "PAuthGeneric", NULL) \ + /* Generic authentication uses QARMA. */ \ + V(kPAuthGenericQARMA, "PAuthGenericQARMA", NULL) \ + /* JavaScript-style FP <-> integer conversion instruction: FJCVTZS. */ \ + V(kJSCVT, "JSCVT", "jscvt") \ + /* RCpc-based model (for weaker release consistency): LDAPR and variants. */ \ + V(kRCpc, "RCpc", "lrcpc") \ + /* Complex number support for NEON: FCMLA and FCADD. */ \ + V(kFcma, "Fcma", "fcma") +// clang-format on + + +class CPUFeaturesConstIterator; + +// A representation of the set of features known to be supported by the target +// device. Each feature is represented by a simple boolean flag. +// +// - TODO: When the Assembler is asked to assemble an instruction, it should +// assert (in debug mode) that the necessary features are available. +// +// - TODO: The Simulator assumes that all features are available by default, +// but it should be possible to configure it to either warn or fail if the +// simulated code uses features that are not enabled. +// +// - TODO: The Disassembler disassembles all instructions that it knows, but +// it could be (optionally) configured to warn if the code uses features or +// instructions that are not available. +// +// - TODO: The MacroAssembler relies on the Assembler's assertions, but in +// some cases it may be useful for macros to generate a fall-back sequence +// in case features are not available. +// +// Expected usage: +// +// // By default, VIXL uses CPUFeatures::AArch64LegacyBaseline(), for +// // compatibility with older version of VIXL. +// MacroAssembler masm; +// +// // Generate code only for the current CPU. +// masm.SetCPUFeatures(CPUFeatures::InferFromOS()); +// +// // Turn off feature checking entirely. +// masm.SetCPUFeatures(CPUFeatures::All()); +// +// Feature set manipulation: +// +// CPUFeatures f; // The default constructor gives an empty set. +// // Individual features can be added (or removed). +// f.Combine(CPUFeatures::kFP, CPUFeatures::kNEON, CPUFeatures::AES); +// f.Remove(CPUFeatures::kNEON); +// +// // Some helpers exist for extensions that provide several features. +// f.Remove(CPUFeatures::All()); +// f.Combine(CPUFeatures::AArch64LegacyBaseline()); +// +// // Chained construction is also possible. +// CPUFeatures g = +// f.With(CPUFeatures::kPmull1Q).Without(CPUFeatures::kCRC32); +// +// // Features can be queried. Where multiple features are given, they are +// // combined with logical AND. +// if (h.Has(CPUFeatures::kNEON)) { ... } +// if (h.Has(CPUFeatures::kFP, CPUFeatures::kNEON)) { ... } +// if (h.Has(g)) { ... } +// // If the empty set is requested, the result is always 'true'. +// VIXL_ASSERT(h.Has(CPUFeatures())); +// +// // For debug and reporting purposes, features can be enumerated (or +// // printed directly): +// std::cout << CPUFeatures::kNEON; // Prints something like "NEON". +// std::cout << f; // Prints something like "FP, NEON, CRC32". +class CPUFeatures { + public: + // clang-format off + // Individual features. + // These should be treated as opaque tokens. User code should not rely on + // specific numeric values or ordering. + enum Feature { + // Refer to VIXL_CPU_FEATURE_LIST (above) for the list of feature names that + // this class supports. + +#define VIXL_DECLARE_FEATURE(SYMBOL, NAME, CPUINFO) SYMBOL, + VIXL_CPU_FEATURE_LIST(VIXL_DECLARE_FEATURE) +#undef VIXL_DECLARE_FEATURE + kNone, + kNumberOfFeatures = kNone + }; + // clang-format on + + // By default, construct with no features enabled. + CPUFeatures() : features_(0) {} + + // Construct with some features already enabled. + CPUFeatures(Feature feature0, + Feature feature1 = kNone, + Feature feature2 = kNone, + Feature feature3 = kNone); + + // Construct with all features enabled. This can be used to disable feature + // checking: `Has(...)` returns true regardless of the argument. + static CPUFeatures All(); + + // The presence of these features was assumed by version of VIXL before this + // API was added, so using this set by default ensures API compatibility. + static CPUFeatures AArch64LegacyBaseline() { + return CPUFeatures(kFP, kNEON, kCRC32); + } + + // Construct a new CPUFeatures object based on what the OS reports. + static CPUFeatures InferFromOS(); + + // Combine another CPUFeatures object into this one. Features that already + // exist in this set are left unchanged. + void Combine(const CPUFeatures& other); + + // Combine specific features into this set. Features that already exist in + // this set are left unchanged. + void Combine(Feature feature0, + Feature feature1 = kNone, + Feature feature2 = kNone, + Feature feature3 = kNone); + + // Remove features in another CPUFeatures object from this one. + void Remove(const CPUFeatures& other); + + // Remove specific features from this set. + void Remove(Feature feature0, + Feature feature1 = kNone, + Feature feature2 = kNone, + Feature feature3 = kNone); + + // Chaining helpers for convenient construction. + CPUFeatures With(const CPUFeatures& other) const; + CPUFeatures With(Feature feature0, + Feature feature1 = kNone, + Feature feature2 = kNone, + Feature feature3 = kNone) const; + CPUFeatures Without(const CPUFeatures& other) const; + CPUFeatures Without(Feature feature0, + Feature feature1 = kNone, + Feature feature2 = kNone, + Feature feature3 = kNone) const; + + // Query features. + // Note that an empty query (like `Has(kNone)`) always returns true. + bool Has(const CPUFeatures& other) const; + bool Has(Feature feature0, + Feature feature1 = kNone, + Feature feature2 = kNone, + Feature feature3 = kNone) const; + + typedef CPUFeaturesConstIterator const_iterator; + + const_iterator begin() const; + const_iterator end() const; + + private: + // Each bit represents a feature. This field will be replaced as needed if + // features are added. + uint64_t features_; + + friend std::ostream& operator<<(std::ostream& os, + const vixl::CPUFeatures& features); +}; + +std::ostream& operator<<(std::ostream& os, vixl::CPUFeatures::Feature feature); +std::ostream& operator<<(std::ostream& os, const vixl::CPUFeatures& features); + +// This is not a proper C++ iterator type, but it simulates enough of +// ForwardIterator that simple loops can be written. +class CPUFeaturesConstIterator { + public: + CPUFeaturesConstIterator(const CPUFeatures* cpu_features = NULL, + CPUFeatures::Feature start = CPUFeatures::kNone) + : cpu_features_(cpu_features), feature_(start) { + VIXL_ASSERT(IsValid()); + } + + bool operator==(const CPUFeaturesConstIterator& other) const; + bool operator!=(const CPUFeaturesConstIterator& other) const { + return !(*this == other); + } + CPUFeatures::Feature operator++(); + CPUFeatures::Feature operator++(int); + + CPUFeatures::Feature operator*() const { + VIXL_ASSERT(IsValid()); + return feature_; + } + + // For proper support of C++'s simplest "Iterator" concept, this class would + // have to define member types (such as CPUFeaturesIterator::pointer) to make + // it appear as if it iterates over Feature objects in memory. That is, we'd + // need CPUFeatures::iterator to behave like std::vector<Feature>::iterator. + // This is at least partially possible -- the std::vector<bool> specialisation + // does something similar -- but it doesn't seem worthwhile for a + // special-purpose debug helper, so they are omitted here. + private: + const CPUFeatures* cpu_features_; + CPUFeatures::Feature feature_; + + bool IsValid() const { + return ((cpu_features_ == NULL) && (feature_ == CPUFeatures::kNone)) || + cpu_features_->Has(feature_); + } +}; + +// A convenience scope for temporarily modifying a CPU features object. This +// allows features to be enabled for short sequences. +// +// Expected usage: +// +// { +// CPUFeaturesScope cpu(&masm, CPUFeatures::kCRC32); +// // This scope can now use CRC32, as well as anything else that was enabled +// // before the scope. +// +// ... +// +// // At the end of the scope, the original CPU features are restored. +// } +class CPUFeaturesScope { + public: + // Start a CPUFeaturesScope on any object that implements + // `CPUFeatures* GetCPUFeatures()`. + template <typename T> + explicit CPUFeaturesScope(T* cpu_features_wrapper, + CPUFeatures::Feature feature0 = CPUFeatures::kNone, + CPUFeatures::Feature feature1 = CPUFeatures::kNone, + CPUFeatures::Feature feature2 = CPUFeatures::kNone, + CPUFeatures::Feature feature3 = CPUFeatures::kNone) + : cpu_features_(cpu_features_wrapper->GetCPUFeatures()), + old_features_(*cpu_features_) { + cpu_features_->Combine(feature0, feature1, feature2, feature3); + } + + template <typename T> + CPUFeaturesScope(T* cpu_features_wrapper, const CPUFeatures& other) + : cpu_features_(cpu_features_wrapper->GetCPUFeatures()), + old_features_(*cpu_features_) { + cpu_features_->Combine(other); + } + + ~CPUFeaturesScope() { *cpu_features_ = old_features_; } + + // For advanced usage, the CPUFeatures object can be accessed directly. + // The scope will restore the original state when it ends. + + CPUFeatures* GetCPUFeatures() const { return cpu_features_; } + + void SetCPUFeatures(const CPUFeatures& cpu_features) { + *cpu_features_ = cpu_features; + } + + private: + CPUFeatures* const cpu_features_; + const CPUFeatures old_features_; +}; + + +} // namespace vixl + +#endif // VIXL_CPU_FEATURES_H |