diff options
Diffstat (limited to 'library/stdarch/crates/std_detect')
4 files changed, 158 insertions, 12 deletions
diff --git a/library/stdarch/crates/std_detect/src/detect/cache.rs b/library/stdarch/crates/std_detect/src/detect/cache.rs index 3056c28a806..83bcedea612 100644 --- a/library/stdarch/crates/std_detect/src/detect/cache.rs +++ b/library/stdarch/crates/std_detect/src/detect/cache.rs @@ -31,7 +31,7 @@ const CACHE_CAPACITY: u32 = 93; /// This type is used to initialize the cache // The derived `Default` implementation will initialize the field to zero, // which is what we want. -#[derive(Copy, Clone, Default)] +#[derive(Copy, Clone, Default, PartialEq, Eq)] pub(crate) struct Initializer(u128); // NOTE: the `debug_assert!` would catch that we do not add more Features than diff --git a/library/stdarch/crates/std_detect/src/detect/mod.rs b/library/stdarch/crates/std_detect/src/detect/mod.rs index a61400a5553..8fd3d957932 100644 --- a/library/stdarch/crates/std_detect/src/detect/mod.rs +++ b/library/stdarch/crates/std_detect/src/detect/mod.rs @@ -49,6 +49,9 @@ cfg_if! { #[path = "os/x86.rs"] mod os; } else if #[cfg(all(any(target_os = "linux", target_os = "android"), feature = "libc"))] { + #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))] + #[path = "os/riscv.rs"] + mod riscv; #[path = "os/linux/mod.rs"] mod os; } else if #[cfg(all(target_os = "freebsd", feature = "libc"))] { diff --git a/library/stdarch/crates/std_detect/src/detect/os/linux/riscv.rs b/library/stdarch/crates/std_detect/src/detect/os/linux/riscv.rs index 33deba93355..6cdc72dff5a 100644 --- a/library/stdarch/crates/std_detect/src/detect/os/linux/riscv.rs +++ b/library/stdarch/crates/std_detect/src/detect/os/linux/riscv.rs @@ -1,5 +1,6 @@ //! Run-time feature detection for RISC-V on Linux. +use super::super::riscv::imply_features; use super::auxvec; use crate::detect::{Feature, bit, cache}; @@ -12,22 +13,16 @@ pub(crate) fn detect_features() -> cache::Initializer { } }; - // Use auxiliary vector to enable single-letter ISA extensions and Zicsr. + // Use auxiliary vector to enable single-letter ISA extensions. // The values are part of the platform-specific [asm/hwcap.h][hwcap] // // [hwcap]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/riscv/include/uapi/asm/hwcap.h?h=v6.14 let auxv = auxvec::auxv().expect("read auxvec"); // should not fail on RISC-V platform #[allow(clippy::eq_op)] - let has_a = bit::test(auxv.hwcap, (b'a' - b'a').into()); - enable_feature(Feature::a, has_a); - enable_feature(Feature::zalrsc, has_a); - enable_feature(Feature::zaamo, has_a); + enable_feature(Feature::a, bit::test(auxv.hwcap, (b'a' - b'a').into())); enable_feature(Feature::c, bit::test(auxv.hwcap, (b'c' - b'a').into())); - let has_d = bit::test(auxv.hwcap, (b'd' - b'a').into()); - let has_f = bit::test(auxv.hwcap, (b'f' - b'a').into()); - enable_feature(Feature::d, has_d); - enable_feature(Feature::f, has_d | has_f); - enable_feature(Feature::zicsr, has_d | has_f); + enable_feature(Feature::d, bit::test(auxv.hwcap, (b'd' - b'a').into())); + enable_feature(Feature::f, bit::test(auxv.hwcap, (b'f' - b'a').into())); enable_feature(Feature::h, bit::test(auxv.hwcap, (b'h' - b'a').into())); enable_feature(Feature::m, bit::test(auxv.hwcap, (b'm' - b'a').into())); @@ -48,5 +43,5 @@ pub(crate) fn detect_features() -> cache::Initializer { // to detect when Rust is used to write Linux kernel modules. // These should be more than Auxvec way to detect supervisor features. - value + imply_features(value) } diff --git a/library/stdarch/crates/std_detect/src/detect/os/riscv.rs b/library/stdarch/crates/std_detect/src/detect/os/riscv.rs new file mode 100644 index 00000000000..b268eff8a14 --- /dev/null +++ b/library/stdarch/crates/std_detect/src/detect/os/riscv.rs @@ -0,0 +1,148 @@ +//! Run-time feature detection utility for RISC-V. +//! +//! On RISC-V, full feature detection needs a help of one or more +//! feature detection mechanisms (usually provided by the operating system). +//! +//! RISC-V architecture defines many extensions and some have dependency to others. +//! More importantly, some of them cannot be enabled without resolving such +//! dependencies due to limited set of features that such mechanisms provide. +//! +//! This module provides an OS-independent utility to process such relations +//! between RISC-V extensions. + +use crate::detect::{Feature, cache}; + +/// Imply features by the given set of enabled features. +/// +/// Note that it does not perform any consistency checks including existence of +/// conflicting extensions and/or complicated requirements. Eliminating such +/// inconsistencies is the responsibility of the feature detection logic and +/// its provider(s). +pub(crate) fn imply_features(mut value: cache::Initializer) -> cache::Initializer { + loop { + // Check convergence of the feature flags later. + let prev = value; + + // Expect that the optimizer turns repeated operations into + // a fewer number of bit-manipulation operations. + macro_rules! imply { + // Regular implication: + // A1 => (B1[, B2...]), A2 => (B1[, B2...]) and so on. + ($($from: ident)|+ => $($to: ident)&+) => { + if [$(Feature::$from as u32),+].iter().any(|&x| value.test(x)) { + $( + value.set(Feature::$to as u32); + )+ + } + }; + // Implication with multiple requirements: + // A1 && A2 ... => (B1[, B2...]). + ($($from: ident)&+ => $($to: ident)&+) => { + if [$(Feature::$from as u32),+].iter().all(|&x| value.test(x)) { + $( + value.set(Feature::$to as u32); + )+ + } + }; + } + macro_rules! group { + ($group: ident == $($member: ident)&+) => { + // Forward implication as defined in the specifications. + imply!($group => $($member)&+); + // Reverse implication to "group extension" from its members. + // This is not a part of specifications but convenient for + // feature detection and implemented in e.g. LLVM. + imply!($($member)&+ => $group); + }; + } + + /* + If a dependency/implication is not explicitly stated in the + specification, it is denoted as a comment as follows: + "defined as subset": + The latter extension is described as a subset of the former + (but the evidence is weak). + */ + + imply!(zbc => zbkc); // defined as subset + group!(zkn == zbkb & zbkc & zbkx & zkne & zknd & zknh); + group!(zks == zbkb & zbkc & zbkx & zksed & zksh); + group!(zk == zkn & zkr & zkt); + + group!(a == zalrsc & zaamo); + + group!(b == zba & zbb & zbs); + + imply!(zhinx => zhinxmin); + imply!(zdinx | zhinxmin => zfinx); + + imply!(zfh => zfhmin); + imply!(q => d); + imply!(d | zfhmin => f); + + imply!(zicntr | zihpm | f | zfinx => zicsr); + imply!(s | h => zicsr); + + // Loop until the feature flags converge. + if prev == value { + return value; + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn simple_direct() { + let mut value = cache::Initializer::default(); + value.set(Feature::f as u32); + // F (and other extensions with CSRs) -> Zicsr + assert!(imply_features(value).test(Feature::zicsr as u32)); + } + + #[test] + fn simple_indirect() { + let mut value = cache::Initializer::default(); + value.set(Feature::q as u32); + // Q -> D, D -> F, F -> Zicsr + assert!(imply_features(value).test(Feature::zicsr as u32)); + } + + #[test] + fn group_simple_forward() { + let mut value = cache::Initializer::default(); + // A -> Zalrsc & Zaamo (forward implication) + value.set(Feature::a as u32); + let value = imply_features(value); + assert!(value.test(Feature::zalrsc as u32)); + assert!(value.test(Feature::zaamo as u32)); + } + + #[test] + fn group_simple_backward() { + let mut value = cache::Initializer::default(); + // Zalrsc & Zaamo -> A (reverse implication) + value.set(Feature::zalrsc as u32); + value.set(Feature::zaamo as u32); + assert!(imply_features(value).test(Feature::a as u32)); + } + + #[test] + fn group_complex_convergence() { + let mut value = cache::Initializer::default(); + // Needs 2 iterations to converge + // (and 3rd iteration for convergence checking): + // 1. [Zk] -> Zkn & Zkr & Zkt + // 2. Zkn -> {Zbkb} & {Zbkc} & {Zbkx} & {Zkne} & {Zknd} & {Zknh} + value.set(Feature::zk as u32); + let value = imply_features(value); + assert!(value.test(Feature::zbkb as u32)); + assert!(value.test(Feature::zbkc as u32)); + assert!(value.test(Feature::zbkx as u32)); + assert!(value.test(Feature::zkne as u32)); + assert!(value.test(Feature::zknd as u32)); + assert!(value.test(Feature::zknh as u32)); + } +} |