| //! Run-time feature detection for ARM on Linux. |
| |
| use crate::detect::{Feature, cache, bit}; |
| use super::{auxvec, cpuinfo}; |
| |
| /// Performs run-time feature detection. |
| #[inline] |
| pub fn check_for(x: Feature) -> bool { |
| cache::test(x as u32, detect_features) |
| } |
| |
| /// Try to read the features from the auxiliary vector, and if that fails, try |
| /// to read them from /proc/cpuinfo. |
| fn detect_features() -> cache::Initializer { |
| let mut value = cache::Initializer::default(); |
| let enable_feature = |value: &mut cache::Initializer, f, enable| { |
| if enable { |
| value.set(f as u32); |
| } |
| }; |
| |
| // The values are part of the platform-specific [asm/hwcap.h][hwcap] |
| // |
| // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h |
| if let Ok(auxv) = auxvec::auxv() { |
| enable_feature(&mut value, Feature::neon, bit::test(auxv.hwcap, 12)); |
| enable_feature(&mut value, Feature::pmull, bit::test(auxv.hwcap2, 1)); |
| return value; |
| } |
| |
| if let Ok(c) = cpuinfo::CpuInfo::new() { |
| enable_feature(&mut value, Feature::neon, c.field("Features").has("neon") && |
| !has_broken_neon(&c)); |
| enable_feature(&mut value, Feature::pmull, c.field("Features").has("pmull")); |
| return value; |
| } |
| value |
| } |
| |
| /// Is the CPU known to have a broken NEON unit? |
| /// |
| /// See https://crbug.com/341598. |
| fn has_broken_neon(cpuinfo: &cpuinfo::CpuInfo) -> bool { |
| cpuinfo.field("CPU implementer") == "0x51" |
| && cpuinfo.field("CPU architecture") == "7" |
| && cpuinfo.field("CPU variant") == "0x1" |
| && cpuinfo.field("CPU part") == "0x04d" |
| && cpuinfo.field("CPU revision") == "0" |
| } |