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Diffstat (limited to 'library/stdarch/crates/std_detect/src/detect/os/x86.rs')
| -rw-r--r-- | library/stdarch/crates/std_detect/src/detect/os/x86.rs | 273 |
1 files changed, 273 insertions, 0 deletions
diff --git a/library/stdarch/crates/std_detect/src/detect/os/x86.rs b/library/stdarch/crates/std_detect/src/detect/os/x86.rs new file mode 100644 index 000000000..ea5f595ec --- /dev/null +++ b/library/stdarch/crates/std_detect/src/detect/os/x86.rs @@ -0,0 +1,273 @@ +//! x86 run-time feature detection is OS independent. + +#[cfg(target_arch = "x86")] +use core::arch::x86::*; +#[cfg(target_arch = "x86_64")] +use core::arch::x86_64::*; + +use core::mem; + +use crate::detect::{bit, cache, Feature}; + +/// Run-time feature detection on x86 works by using the CPUID instruction. +/// +/// The [CPUID Wikipedia page][wiki_cpuid] contains +/// all the information about which flags to set to query which values, and in +/// which registers these are reported. +/// +/// The definitive references are: +/// - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2: +/// Instruction Set Reference, A-Z][intel64_ref]. +/// - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and +/// System Instructions][amd64_ref]. +/// +/// [wiki_cpuid]: https://en.wikipedia.org/wiki/CPUID +/// [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf +/// [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf +#[allow(clippy::similar_names)] +pub(crate) fn detect_features() -> cache::Initializer { + let mut value = cache::Initializer::default(); + + // If the x86 CPU does not support the CPUID instruction then it is too + // old to support any of the currently-detectable features. + if !has_cpuid() { + return value; + } + + // Calling `__cpuid`/`__cpuid_count` from here on is safe because the CPU + // has `cpuid` support. + + // 0. EAX = 0: Basic Information: + // - EAX returns the "Highest Function Parameter", that is, the maximum + // leaf value for subsequent calls of `cpuinfo` in range [0, + // 0x8000_0000]. - The vendor ID is stored in 12 u8 ascii chars, + // returned in EBX, EDX, and ECX (in that order): + let (max_basic_leaf, vendor_id) = unsafe { + let CpuidResult { + eax: max_basic_leaf, + ebx, + ecx, + edx, + } = __cpuid(0); + let vendor_id: [[u8; 4]; 3] = [ + mem::transmute(ebx), + mem::transmute(edx), + mem::transmute(ecx), + ]; + let vendor_id: [u8; 12] = mem::transmute(vendor_id); + (max_basic_leaf, vendor_id) + }; + + if max_basic_leaf < 1 { + // Earlier Intel 486, CPUID not implemented + return value; + } + + // EAX = 1, ECX = 0: Queries "Processor Info and Feature Bits"; + // Contains information about most x86 features. + let CpuidResult { + ecx: proc_info_ecx, + edx: proc_info_edx, + .. + } = unsafe { __cpuid(0x0000_0001_u32) }; + + // EAX = 7, ECX = 0: Queries "Extended Features"; + // Contains information about bmi,bmi2, and avx2 support. + let (extended_features_ebx, extended_features_ecx) = if max_basic_leaf >= 7 { + let CpuidResult { ebx, ecx, .. } = unsafe { __cpuid(0x0000_0007_u32) }; + (ebx, ecx) + } else { + (0, 0) // CPUID does not support "Extended Features" + }; + + // EAX = 0x8000_0000, ECX = 0: Get Highest Extended Function Supported + // - EAX returns the max leaf value for extended information, that is, + // `cpuid` calls in range [0x8000_0000; u32::MAX]: + let CpuidResult { + eax: extended_max_basic_leaf, + .. + } = unsafe { __cpuid(0x8000_0000_u32) }; + + // EAX = 0x8000_0001, ECX=0: Queries "Extended Processor Info and Feature + // Bits" + let extended_proc_info_ecx = if extended_max_basic_leaf >= 1 { + let CpuidResult { ecx, .. } = unsafe { __cpuid(0x8000_0001_u32) }; + ecx + } else { + 0 + }; + + { + // borrows value till the end of this scope: + let mut enable = |r, rb, f| { + if bit::test(r as usize, rb) { + value.set(f as u32); + } + }; + + enable(proc_info_ecx, 0, Feature::sse3); + enable(proc_info_ecx, 1, Feature::pclmulqdq); + enable(proc_info_ecx, 9, Feature::ssse3); + enable(proc_info_ecx, 13, Feature::cmpxchg16b); + enable(proc_info_ecx, 19, Feature::sse4_1); + enable(proc_info_ecx, 20, Feature::sse4_2); + enable(proc_info_ecx, 23, Feature::popcnt); + enable(proc_info_ecx, 25, Feature::aes); + enable(proc_info_ecx, 29, Feature::f16c); + enable(proc_info_ecx, 30, Feature::rdrand); + enable(extended_features_ebx, 18, Feature::rdseed); + enable(extended_features_ebx, 19, Feature::adx); + enable(extended_features_ebx, 11, Feature::rtm); + enable(proc_info_edx, 4, Feature::tsc); + enable(proc_info_edx, 23, Feature::mmx); + enable(proc_info_edx, 24, Feature::fxsr); + enable(proc_info_edx, 25, Feature::sse); + enable(proc_info_edx, 26, Feature::sse2); + enable(extended_features_ebx, 29, Feature::sha); + + enable(extended_features_ebx, 3, Feature::bmi1); + enable(extended_features_ebx, 8, Feature::bmi2); + + // `XSAVE` and `AVX` support: + let cpu_xsave = bit::test(proc_info_ecx as usize, 26); + if cpu_xsave { + // 0. Here the CPU supports `XSAVE`. + + // 1. Detect `OSXSAVE`, that is, whether the OS is AVX enabled and + // supports saving the state of the AVX/AVX2 vector registers on + // context-switches, see: + // + // - [intel: is avx enabled?][is_avx_enabled], + // - [mozilla: sse.cpp][mozilla_sse_cpp]. + // + // [is_avx_enabled]: https://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled + // [mozilla_sse_cpp]: https://hg.mozilla.org/mozilla-central/file/64bab5cbb9b6/mozglue/build/SSE.cpp#l190 + let cpu_osxsave = bit::test(proc_info_ecx as usize, 27); + + if cpu_osxsave { + // 2. The OS must have signaled the CPU that it supports saving and + // restoring the: + // + // * SSE -> `XCR0.SSE[1]` + // * AVX -> `XCR0.AVX[2]` + // * AVX-512 -> `XCR0.AVX-512[7:5]`. + // + // by setting the corresponding bits of `XCR0` to `1`. + // + // This is safe because the CPU supports `xsave` + // and the OS has set `osxsave`. + let xcr0 = unsafe { _xgetbv(0) }; + // Test `XCR0.SSE[1]` and `XCR0.AVX[2]` with the mask `0b110 == 6`: + let os_avx_support = xcr0 & 6 == 6; + // Test `XCR0.AVX-512[7:5]` with the mask `0b1110_0000 == 224`: + let os_avx512_support = xcr0 & 224 == 224; + + // Only if the OS and the CPU support saving/restoring the AVX + // registers we enable `xsave` support: + if os_avx_support { + // See "13.3 ENABLING THE XSAVE FEATURE SET AND XSAVE-ENABLED + // FEATURES" in the "Intel® 64 and IA-32 Architectures Software + // Developer’s Manual, Volume 1: Basic Architecture": + // + // "Software enables the XSAVE feature set by setting + // CR4.OSXSAVE[bit 18] to 1 (e.g., with the MOV to CR4 + // instruction). If this bit is 0, execution of any of XGETBV, + // XRSTOR, XRSTORS, XSAVE, XSAVEC, XSAVEOPT, XSAVES, and XSETBV + // causes an invalid-opcode exception (#UD)" + // + enable(proc_info_ecx, 26, Feature::xsave); + + // For `xsaveopt`, `xsavec`, and `xsaves` we need to query: + // Processor Extended State Enumeration Sub-leaf (EAX = 0DH, + // ECX = 1): + if max_basic_leaf >= 0xd { + let CpuidResult { + eax: proc_extended_state1_eax, + .. + } = unsafe { __cpuid_count(0xd_u32, 1) }; + enable(proc_extended_state1_eax, 0, Feature::xsaveopt); + enable(proc_extended_state1_eax, 1, Feature::xsavec); + enable(proc_extended_state1_eax, 3, Feature::xsaves); + } + + // FMA (uses 256-bit wide registers): + enable(proc_info_ecx, 12, Feature::fma); + + // And AVX/AVX2: + enable(proc_info_ecx, 28, Feature::avx); + enable(extended_features_ebx, 5, Feature::avx2); + + // For AVX-512 the OS also needs to support saving/restoring + // the extended state, only then we enable AVX-512 support: + if os_avx512_support { + enable(extended_features_ebx, 16, Feature::avx512f); + enable(extended_features_ebx, 17, Feature::avx512dq); + enable(extended_features_ebx, 21, Feature::avx512ifma); + enable(extended_features_ebx, 26, Feature::avx512pf); + enable(extended_features_ebx, 27, Feature::avx512er); + enable(extended_features_ebx, 28, Feature::avx512cd); + enable(extended_features_ebx, 30, Feature::avx512bw); + enable(extended_features_ebx, 31, Feature::avx512vl); + enable(extended_features_ecx, 1, Feature::avx512vbmi); + enable(extended_features_ecx, 5, Feature::avx512bf16); + enable(extended_features_ecx, 6, Feature::avx512vbmi2); + enable(extended_features_ecx, 8, Feature::avx512gfni); + enable(extended_features_ecx, 8, Feature::avx512vp2intersect); + enable(extended_features_ecx, 9, Feature::avx512vaes); + enable(extended_features_ecx, 10, Feature::avx512vpclmulqdq); + enable(extended_features_ecx, 11, Feature::avx512vnni); + enable(extended_features_ecx, 12, Feature::avx512bitalg); + enable(extended_features_ecx, 14, Feature::avx512vpopcntdq); + } + } + } + } + + // This detects ABM on AMD CPUs and LZCNT on Intel CPUs. + // On intel CPUs with popcnt, lzcnt implements the + // "missing part" of ABM, so we map both to the same + // internal feature. + // + // The `is_x86_feature_detected!("lzcnt")` macro then + // internally maps to Feature::abm. + enable(extended_proc_info_ecx, 5, Feature::lzcnt); + + // As Hygon Dhyana originates from AMD technology and shares most of the architecture with + // AMD's family 17h, but with different CPU Vendor ID("HygonGenuine")/Family series + // number(Family 18h). + // + // For CPUID feature bits, Hygon Dhyana(family 18h) share the same definition with AMD + // family 17h. + // + // Related AMD CPUID specification is https://www.amd.com/system/files/TechDocs/25481.pdf. + // Related Hygon kernel patch can be found on + // http://lkml.kernel.org/r/5ce86123a7b9dad925ac583d88d2f921040e859b.1538583282.git.puwen@hygon.cn + if vendor_id == *b"AuthenticAMD" || vendor_id == *b"HygonGenuine" { + // These features are available on AMD arch CPUs: + enable(extended_proc_info_ecx, 6, Feature::sse4a); + enable(extended_proc_info_ecx, 21, Feature::tbm); + } + } + + // Unfortunately, some Skylake chips erroneously report support for BMI1 and + // BMI2 without actual support. These chips don't support AVX, and it seems + // that all Intel chips with non-erroneous support BMI do (I didn't check + // other vendors), so we can disable these flags for chips that don't also + // report support for AVX. + // + // It's possible this will pessimize future chips that do support BMI and + // not AVX, but this seems minor compared to a hard crash you get when + // executing an unsupported instruction (to put it another way, it's safe + // for us to under-report CPU features, but not to over-report them). Still, + // to limit any impact this may have in the future, we only do this for + // Intel chips, as it's a bug only present in their chips. + // + // This bug is documented as `SKL052` in the errata section of this document: + // http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/desktop-6th-gen-core-family-spec-update.pdf + if vendor_id == *b"GenuineIntel" && !value.test(Feature::avx as u32) { + value.unset(Feature::bmi1 as u32); + value.unset(Feature::bmi2 as u32); + } + + value +} |