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