diff --git a/crates/std_detect/src/detect/cache.rs b/crates/std_detect/src/detect/cache.rs index fe2abf5cf5..d421037f69 100644 --- a/crates/std_detect/src/detect/cache.rs +++ b/crates/std_detect/src/detect/cache.rs @@ -5,11 +5,7 @@ use crate::sync::atomic::Ordering; -#[cfg(target_pointer_width = "64")] -use crate::sync::atomic::AtomicU64; - -#[cfg(target_pointer_width = "32")] -use crate::sync::atomic::AtomicU32; +use crate::sync::atomic::AtomicUsize; /// Sets the `bit` of `x`. #[inline] @@ -30,7 +26,7 @@ const fn unset_bit(x: u64, bit: u32) -> u64 { } /// Maximum number of features that can be cached. -const CACHE_CAPACITY: u32 = 63; +const CACHE_CAPACITY: u32 = 62; /// This type is used to initialize the cache #[derive(Copy, Clone)] @@ -81,83 +77,48 @@ impl Initializer { } /// This global variable is a cache of the features supported by the CPU. -static CACHE: Cache = Cache::uninitialized(); +// Note: on x64, we only use the first slot +static CACHE: [Cache; 2] = [Cache::uninitialized(), Cache::uninitialized()]; -/// Feature cache with capacity for `CACHE_CAPACITY` features. +/// Feature cache with capacity for `usize::max_value() - 1` features. /// /// Note: the last feature bit is used to represent an /// uninitialized cache. -#[cfg(target_pointer_width = "64")] -struct Cache(AtomicU64); +/// +/// Note: we can use `Relaxed` atomic operations, because we are only interested +/// in the effects of operations on a single memory location. That is, we only +/// need "modification order", and not the full-blown "happens before". However, +/// we use `SeqCst` just to be on the safe side. +struct Cache(AtomicUsize); -#[cfg(target_pointer_width = "64")] -#[allow(clippy::use_self)] impl Cache { + const CAPACITY: u32 = (core::mem::size_of::() * 8 - 1) as u32; + const MASK: usize = (1 << Cache::CAPACITY) - 1; + /// Creates an uninitialized cache. #[allow(clippy::declare_interior_mutable_const)] const fn uninitialized() -> Self { - Cache(AtomicU64::new(u64::max_value())) + Cache(AtomicUsize::new(usize::max_value())) } /// Is the cache uninitialized? #[inline] pub(crate) fn is_uninitialized(&self) -> bool { - self.0.load(Ordering::Relaxed) == u64::max_value() + self.0.load(Ordering::SeqCst) == usize::max_value() } /// Is the `bit` in the cache set? #[inline] pub(crate) fn test(&self, bit: u32) -> bool { - test_bit(CACHE.0.load(Ordering::Relaxed), bit) + test_bit(self.0.load(Ordering::SeqCst) as u64, bit) } /// Initializes the cache. #[inline] - pub(crate) fn initialize(&self, value: Initializer) { - self.0.store(value.0, Ordering::Relaxed); + fn initialize(&self, value: usize) { + self.0.store(value, Ordering::SeqCst); } } -/// Feature cache with capacity for `CACHE_CAPACITY` features. -/// -/// Note: the last feature bit is used to represent an -/// uninitialized cache. -#[cfg(target_pointer_width = "32")] -struct Cache(AtomicU32, AtomicU32); - -#[cfg(target_pointer_width = "32")] -impl Cache { - /// Creates an uninitialized cache. - const fn uninitialized() -> Self { - Cache( - AtomicU32::new(u32::max_value()), - AtomicU32::new(u32::max_value()), - ) - } - /// Is the cache uninitialized? - #[inline] - pub(crate) fn is_uninitialized(&self) -> bool { - self.1.load(Ordering::Relaxed) == u32::max_value() - } - - /// Is the `bit` in the cache set? - #[inline] - pub(crate) fn test(&self, bit: u32) -> bool { - if bit < 32 { - test_bit(CACHE.0.load(Ordering::Relaxed) as u64, bit) - } else { - test_bit(CACHE.1.load(Ordering::Relaxed) as u64, bit - 32) - } - } - - /// Initializes the cache. - #[inline] - pub(crate) fn initialize(&self, value: Initializer) { - let lo: u32 = value.0 as u32; - let hi: u32 = (value.0 >> 32) as u32; - self.0.store(lo, Ordering::Relaxed); - self.1.store(hi, Ordering::Relaxed); - } -} cfg_if::cfg_if! { if #[cfg(feature = "std_detect_env_override")] { #[inline(never)] @@ -167,16 +128,22 @@ cfg_if::cfg_if! { let _ = super::Feature::from_str(v).map(|v| value.unset(v as u32)); } } - CACHE.initialize(value); + do_initialize(value); } } else { #[inline] fn initialize(value: Initializer) { - CACHE.initialize(value); + do_initialize(value); } } } +#[inline] +fn do_initialize(value: Initializer) { + CACHE[0].initialize((value.0) as usize & Cache::MASK); + CACHE[1].initialize((value.0 >> Cache::CAPACITY) as usize & Cache::MASK); +} + /// Tests the `bit` of the storage. If the storage has not been initialized, /// initializes it with the result of `f()`. /// @@ -194,8 +161,14 @@ pub(crate) fn test(bit: u32, f: F) -> bool where F: FnOnce() -> Initializer, { - if CACHE.is_uninitialized() { - initialize(f()); + let (bit, idx) = if bit < Cache::CAPACITY { + (bit, 0) + } else { + (bit - Cache::CAPACITY, 1) + }; + + if CACHE[idx].is_uninitialized() { + initialize(f()) } - CACHE.test(bit) + CACHE[idx].test(bit) }