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std_detect: RISC-V Linux: Ergonomic querying with riscv_hwprobe #1839

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std_detect: RISC-V Linux: Ergonomic querying with riscv_hwprobe #1839

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83 changes: 42 additions & 41 deletions crates/std_detect/src/detect/os/linux/riscv.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,13 @@ struct riscv_hwprobe {
value: u64,
}

impl riscv_hwprobe {
// key is overwritten to -1 if not supported by riscv_hwprobe syscall.
pub fn get(&self) -> Option<u64> {
(self.key != -1).then_some(self.value)
}
}

#[allow(non_upper_case_globals)]
const __NR_riscv_hwprobe: libc::c_long = 258;

Expand Down Expand Up @@ -156,49 +163,45 @@ pub(crate) fn detect_features() -> cache::Initializer {
// Use riscv_hwprobe syscall to query more extensions and
// performance-related capabilities.
'hwprobe: {
let mut out = [
riscv_hwprobe {
key: RISCV_HWPROBE_KEY_BASE_BEHAVIOR,
value: 0,
},
riscv_hwprobe {
key: RISCV_HWPROBE_KEY_IMA_EXT_0,
value: 0,
},
riscv_hwprobe {
key: RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF,
value: 0,
},
riscv_hwprobe {
key: RISCV_HWPROBE_KEY_MISALIGNED_VECTOR_PERF,
value: 0,
},
riscv_hwprobe {
key: RISCV_HWPROBE_KEY_CPUPERF_0,
value: 0,
},
];
if !_riscv_hwprobe(&mut out) {
macro_rules! init {
{ $($name: ident : $key: expr),* $(,)? } => {
#[repr(usize)]
enum Indices { $($name),* }
let mut t = [$(riscv_hwprobe { key: $key, value: 0 }),*];
macro_rules! data_mut { () => { &mut t } }
macro_rules! query { [$idx: ident] => { t[Indices::$idx as usize].get() } }
}
}
init! {
BaseBehavior: RISCV_HWPROBE_KEY_BASE_BEHAVIOR,
Extensions: RISCV_HWPROBE_KEY_IMA_EXT_0,
MisalignedScalarPerf: RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF,
MisalignedVectorPerf: RISCV_HWPROBE_KEY_MISALIGNED_VECTOR_PERF,
MisalignedScalarPerfFallback: RISCV_HWPROBE_KEY_CPUPERF_0,
};
if !_riscv_hwprobe(data_mut!()) {
break 'hwprobe;
}

// Query scalar/vector misaligned behavior.
if out[2].key != -1 {
// Query scalar misaligned behavior.
if let Some(value) = query![MisalignedScalarPerf] {
enable_feature(
Feature::unaligned_scalar_mem,
out[2].value == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST,
value == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST,
);
} else if out[4].key != -1 {
} else if let Some(value) = query![MisalignedScalarPerfFallback] {
// Deprecated method for fallback
enable_feature(
Feature::unaligned_scalar_mem,
out[4].value & RISCV_HWPROBE_MISALIGNED_MASK == RISCV_HWPROBE_MISALIGNED_FAST,
value & RISCV_HWPROBE_MISALIGNED_MASK == RISCV_HWPROBE_MISALIGNED_FAST,
);
}
if out[3].key != -1 {

// Query vector misaligned behavior.
if let Some(value) = query![MisalignedVectorPerf] {
enable_feature(
Feature::unaligned_vector_mem,
out[3].value == RISCV_HWPROBE_MISALIGNED_VECTOR_FAST,
value == RISCV_HWPROBE_MISALIGNED_VECTOR_FAST,
);
}

Expand All @@ -208,22 +211,20 @@ pub(crate) fn detect_features() -> cache::Initializer {
// 20240411).
// This is a current requirement of
// `RISCV_HWPROBE_KEY_IMA_EXT_0`-based tests.
let has_ima = (out[0].key != -1) && (out[0].value & RISCV_HWPROBE_BASE_BEHAVIOR_IMA != 0);
if !has_ima {
if query![BaseBehavior].is_none_or(|value| value & RISCV_HWPROBE_BASE_BEHAVIOR_IMA == 0) {
break 'hwprobe;
}
has_i |= has_ima;
enable_feature(Feature::zicsr, has_ima);
enable_feature(Feature::zicntr, has_ima);
enable_feature(Feature::zifencei, has_ima);
enable_feature(Feature::m, has_ima);
enable_feature(Feature::a, has_ima);
has_i = true;
enable_feature(Feature::zicsr, true);
enable_feature(Feature::zicntr, true);
enable_feature(Feature::zifencei, true);
enable_feature(Feature::m, true);
enable_feature(Feature::a, true);

// Enable features based on `RISCV_HWPROBE_KEY_IMA_EXT_0`.
if out[1].key == -1 {
let Some(ima_ext_0) = query![Extensions] else {
break 'hwprobe;
}
let ima_ext_0 = out[1].value;
};
let test = |mask| (ima_ext_0 & mask) != 0;

enable_feature(Feature::d, test(RISCV_HWPROBE_IMA_FD)); // F is implied.
Expand Down