src/stdsimd/stdsimd/arch/detect/os/linux/arm.rs

   1 //! Run-time feature detection for ARM on Linux.
   2
   3 use arch::detect::Feature;
   4 use arch::detect::cache;
   5 use arch::detect::bit;
   6 use super::auxvec;
   7 use super::cpuinfo;
   8
   9 /// Performs run-time feature detection.
  10 #[inline]
  11 pub fn check_for(x: Feature) -> bool {
  12     cache::test(x as u32, detect_features)
  13 }
  14
  15 /// Try to read the features from the auxiliary vector, and if that fails, try
  16 /// to read them from /proc/cpuinfo.
  17 fn detect_features() -> cache::Initializer {
  18     let mut value = cache::Initializer::default();
  19     let enable_feature = |value: &mut cache::Initializer, f, enable| {
  20         if enable {
  21             value.set(f as u32);
  22         }
  23     };
  24
  25     // The values are part of the platform-specific [asm/hwcap.h][hwcap]
  26     //
  27     // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm64/include/uapi/asm/hwcap.h
  28     if let Ok(auxv) = auxvec::auxv() {
  29         enable_feature(&mut value, Feature::neon, bit::test(auxv.hwcap, 12));
  30         enable_feature(&mut value, Feature::pmull, bit::test(auxv.hwcap2, 1));
  31         return value;
  32     }
  33
  34     if let Ok(c) = cpuinfo::CpuInfo::new() {
  35         enable_feature(&mut value, Feature::neon, c.field("Features").has("neon") &&
  36             !has_broken_neon(&c));
  37         enable_feature(&mut value, Feature::pmull, c.field("Features").has("pmull"));
  38         return value;
  39     }
  40     value
  41 }
  42
  43 /// Is the CPU known to have a broken NEON unit?
  44 ///
  45 /// See https://crbug.com/341598.
  46 fn has_broken_neon(cpuinfo: &cpuinfo::CpuInfo) -> bool {
  47     cpuinfo.field("CPU implementer") == "0x51"
  48         && cpuinfo.field("CPU architecture") == "7"
  49         && cpuinfo.field("CPU variant") == "0x1"
  50         && cpuinfo.field("CPU part") == "0x04d"
  51         && cpuinfo.field("CPU revision") == "0"
  52 }