Extend the chaining logic to slices too
This commit is contained in:
Scott McMurray
parent
19648ce5cd
commit
756670f40e
4 changed files with 256 additions and 38 deletions
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@ -2053,6 +2053,22 @@ mod impls {
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fn ge(&self, other: &&B) -> bool {
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PartialOrd::ge(*self, *other)
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}
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#[inline]
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fn __chaining_lt(&self, other: &&B) -> ControlFlow<bool> {
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PartialOrd::__chaining_lt(*self, *other)
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}
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#[inline]
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fn __chaining_le(&self, other: &&B) -> ControlFlow<bool> {
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PartialOrd::__chaining_le(*self, *other)
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}
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#[inline]
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fn __chaining_gt(&self, other: &&B) -> ControlFlow<bool> {
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PartialOrd::__chaining_gt(*self, *other)
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}
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#[inline]
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fn __chaining_ge(&self, other: &&B) -> ControlFlow<bool> {
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PartialOrd::__chaining_ge(*self, *other)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A: ?Sized> Ord for &A
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@ -2108,6 +2124,22 @@ mod impls {
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fn ge(&self, other: &&mut B) -> bool {
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PartialOrd::ge(*self, *other)
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}
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#[inline]
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fn __chaining_lt(&self, other: &&mut B) -> ControlFlow<bool> {
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PartialOrd::__chaining_lt(*self, *other)
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}
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#[inline]
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fn __chaining_le(&self, other: &&mut B) -> ControlFlow<bool> {
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PartialOrd::__chaining_le(*self, *other)
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}
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#[inline]
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fn __chaining_gt(&self, other: &&mut B) -> ControlFlow<bool> {
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PartialOrd::__chaining_gt(*self, *other)
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}
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#[inline]
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fn __chaining_ge(&self, other: &&mut B) -> ControlFlow<bool> {
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PartialOrd::__chaining_ge(*self, *other)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A: ?Sized> Ord for &mut A
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@ -5,6 +5,7 @@ use crate::ascii;
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use crate::cmp::{self, BytewiseEq, Ordering};
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use crate::intrinsics::compare_bytes;
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use crate::num::NonZero;
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use crate::ops::ControlFlow;
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, U> PartialEq<[U]> for [T]
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@ -31,12 +32,64 @@ impl<T: Ord> Ord for [T] {
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}
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}
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#[inline]
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fn as_underlying(x: ControlFlow<bool>) -> u8 {
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// SAFETY: This will only compile if `bool` and `ControlFlow<bool>` have the same
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// size (which isn't guaranteed but this is libcore). Because they have the same
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// size, it's a niched implementation, which in one byte means there can't be
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// any uninitialized memory. The callers then only check for `0` or `1` from this,
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// which must necessarily match the `Break` variant, and we're fine no matter
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// what ends up getting picked as the value representing `Continue(())`.
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unsafe { crate::mem::transmute(x) }
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}
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/// Implements comparison of slices [lexicographically](Ord#lexicographical-comparison).
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: PartialOrd> PartialOrd for [T] {
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#[inline]
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fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
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SlicePartialOrd::partial_compare(self, other)
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}
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#[inline]
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fn lt(&self, other: &Self) -> bool {
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// This is certainly not the obvious way to implement these methods.
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// Unfortunately, using anything that looks at the discriminant means that
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// LLVM sees a check for `2` (aka `ControlFlow<bool>::Continue(())`) and
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// gets very distracted by that, ending up generating extraneous code.
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// This should be changed to something simpler once either LLVM is smarter,
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// see <https://github.com/llvm/llvm-project/issues/132678>, or we generate
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// niche discriminant checks in a way that doesn't trigger it.
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as_underlying(self.__chaining_lt(other)) == 1
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}
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#[inline]
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fn le(&self, other: &Self) -> bool {
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as_underlying(self.__chaining_le(other)) != 0
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}
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#[inline]
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fn gt(&self, other: &Self) -> bool {
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as_underlying(self.__chaining_gt(other)) == 1
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}
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#[inline]
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fn ge(&self, other: &Self) -> bool {
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as_underlying(self.__chaining_ge(other)) != 0
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}
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#[inline]
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fn __chaining_lt(&self, other: &Self) -> ControlFlow<bool> {
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SliceChain::chaining_lt(self, other)
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}
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#[inline]
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fn __chaining_le(&self, other: &Self) -> ControlFlow<bool> {
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SliceChain::chaining_le(self, other)
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}
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#[inline]
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fn __chaining_gt(&self, other: &Self) -> ControlFlow<bool> {
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SliceChain::chaining_gt(self, other)
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}
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#[inline]
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fn __chaining_ge(&self, other: &Self) -> ControlFlow<bool> {
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SliceChain::chaining_ge(self, other)
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}
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}
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#[doc(hidden)]
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@ -99,8 +152,51 @@ trait SlicePartialOrd: Sized {
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fn partial_compare(left: &[Self], right: &[Self]) -> Option<Ordering>;
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}
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#[doc(hidden)]
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// intermediate trait for specialization of slice's PartialOrd chaining methods
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trait SliceChain: Sized {
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fn chaining_lt(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
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fn chaining_le(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
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fn chaining_gt(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
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fn chaining_ge(left: &[Self], right: &[Self]) -> ControlFlow<bool>;
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}
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type AlwaysBreak<B> = ControlFlow<B, crate::convert::Infallible>;
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impl<A: PartialOrd> SlicePartialOrd for A {
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default fn partial_compare(left: &[A], right: &[A]) -> Option<Ordering> {
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let elem_chain = |a, b| match PartialOrd::partial_cmp(a, b) {
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Some(Ordering::Equal) => ControlFlow::Continue(()),
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non_eq => ControlFlow::Break(non_eq),
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};
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let len_chain = |a: &_, b: &_| ControlFlow::Break(usize::partial_cmp(a, b));
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let AlwaysBreak::Break(b) = chaining_impl(left, right, elem_chain, len_chain);
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b
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}
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}
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impl<A: PartialOrd> SliceChain for A {
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default fn chaining_lt(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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chaining_impl(left, right, PartialOrd::__chaining_lt, usize::__chaining_lt)
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}
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default fn chaining_le(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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chaining_impl(left, right, PartialOrd::__chaining_le, usize::__chaining_le)
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}
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default fn chaining_gt(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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chaining_impl(left, right, PartialOrd::__chaining_gt, usize::__chaining_gt)
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}
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default fn chaining_ge(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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chaining_impl(left, right, PartialOrd::__chaining_ge, usize::__chaining_ge)
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}
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}
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#[inline]
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fn chaining_impl<'l, 'r, A: PartialOrd, B, C>(
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left: &'l [A],
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right: &'r [A],
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elem_chain: impl Fn(&'l A, &'r A) -> ControlFlow<B>,
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len_chain: impl for<'a> FnOnce(&'a usize, &'a usize) -> ControlFlow<B, C>,
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) -> ControlFlow<B, C> {
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let l = cmp::min(left.len(), right.len());
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// Slice to the loop iteration range to enable bound check
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@ -109,14 +205,10 @@ impl<A: PartialOrd> SlicePartialOrd for A {
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let rhs = &right[..l];
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for i in 0..l {
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match lhs[i].partial_cmp(&rhs[i]) {
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Some(Ordering::Equal) => (),
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non_eq => return non_eq,
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}
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elem_chain(&lhs[i], &rhs[i])?;
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}
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left.len().partial_cmp(&right.len())
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}
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len_chain(&left.len(), &right.len())
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}
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// This is the impl that we would like to have. Unfortunately it's not sound.
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@ -165,21 +257,13 @@ trait SliceOrd: Sized {
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impl<A: Ord> SliceOrd for A {
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default fn compare(left: &[Self], right: &[Self]) -> Ordering {
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let l = cmp::min(left.len(), right.len());
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// Slice to the loop iteration range to enable bound check
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// elimination in the compiler
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let lhs = &left[..l];
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let rhs = &right[..l];
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for i in 0..l {
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match lhs[i].cmp(&rhs[i]) {
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Ordering::Equal => (),
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non_eq => return non_eq,
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}
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}
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left.len().cmp(&right.len())
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let elem_chain = |a, b| match Ord::cmp(a, b) {
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Ordering::Equal => ControlFlow::Continue(()),
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non_eq => ControlFlow::Break(non_eq),
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};
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let len_chain = |a: &_, b: &_| ControlFlow::Break(usize::cmp(a, b));
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let AlwaysBreak::Break(b) = chaining_impl(left, right, elem_chain, len_chain);
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b
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}
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}
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@ -191,7 +275,7 @@ impl<A: Ord> SliceOrd for A {
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/// * For every `x` and `y` of this type, `Ord(x, y)` must return the same
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/// value as `Ord::cmp(transmute::<_, u8>(x), transmute::<_, u8>(y))`.
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#[rustc_specialization_trait]
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unsafe trait UnsignedBytewiseOrd {}
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unsafe trait UnsignedBytewiseOrd: Ord {}
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unsafe impl UnsignedBytewiseOrd for bool {}
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unsafe impl UnsignedBytewiseOrd for u8 {}
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@ -225,6 +309,38 @@ impl<A: Ord + UnsignedBytewiseOrd> SliceOrd for A {
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}
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}
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// Don't generate our own chaining loops for `memcmp`-able things either.
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impl<A: PartialOrd + UnsignedBytewiseOrd> SliceChain for A {
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#[inline]
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fn chaining_lt(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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match SliceOrd::compare(left, right) {
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Ordering::Equal => ControlFlow::Continue(()),
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ne => ControlFlow::Break(ne.is_lt()),
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}
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}
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#[inline]
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fn chaining_le(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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match SliceOrd::compare(left, right) {
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Ordering::Equal => ControlFlow::Continue(()),
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ne => ControlFlow::Break(ne.is_le()),
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}
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}
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#[inline]
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fn chaining_gt(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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match SliceOrd::compare(left, right) {
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Ordering::Equal => ControlFlow::Continue(()),
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ne => ControlFlow::Break(ne.is_gt()),
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}
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}
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#[inline]
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fn chaining_ge(left: &[Self], right: &[Self]) -> ControlFlow<bool> {
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match SliceOrd::compare(left, right) {
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Ordering::Equal => ControlFlow::Continue(()),
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ne => ControlFlow::Break(ne.is_ge()),
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}
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}
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}
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pub(super) trait SliceContains: Sized {
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fn slice_contains(&self, x: &[Self]) -> bool;
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}
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@ -2,7 +2,7 @@
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use crate::cmp::Ordering::{self, *};
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use crate::marker::{ConstParamTy_, StructuralPartialEq, UnsizedConstParamTy};
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use crate::ops::ControlFlow::{Break, Continue};
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use crate::ops::ControlFlow::{self, Break, Continue};
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// Recursive macro for implementing n-ary tuple functions and operations
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//
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@ -95,6 +95,22 @@ macro_rules! tuple_impls {
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fn gt(&self, other: &($($T,)+)) -> bool {
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lexical_ord!(gt, __chaining_gt, $( ${ignore($T)} self.${index()}, other.${index()} ),+)
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}
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#[inline]
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fn __chaining_lt(&self, other: &($($T,)+)) -> ControlFlow<bool> {
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lexical_chain!(__chaining_lt, $( ${ignore($T)} self.${index()}, other.${index()} ),+)
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}
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#[inline]
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fn __chaining_le(&self, other: &($($T,)+)) -> ControlFlow<bool> {
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lexical_chain!(__chaining_le, $( ${ignore($T)} self.${index()}, other.${index()} ),+)
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}
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#[inline]
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fn __chaining_gt(&self, other: &($($T,)+)) -> ControlFlow<bool> {
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lexical_chain!(__chaining_gt, $( ${ignore($T)} self.${index()}, other.${index()} ),+)
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}
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#[inline]
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fn __chaining_ge(&self, other: &($($T,)+)) -> ControlFlow<bool> {
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lexical_chain!(__chaining_ge, $( ${ignore($T)} self.${index()}, other.${index()} ),+)
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}
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}
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}
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@ -187,6 +203,17 @@ macro_rules! lexical_ord {
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};
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}
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// Same parameter interleaving as `lexical_ord` above
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macro_rules! lexical_chain {
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($chain_rel: ident, $a:expr, $b:expr $(,$rest_a:expr, $rest_b:expr)*) => {{
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PartialOrd::$chain_rel(&$a, &$b)?;
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lexical_chain!($chain_rel $(,$rest_a, $rest_b)*)
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}};
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($chain_rel: ident) => {
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Continue(())
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};
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}
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macro_rules! lexical_partial_cmp {
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($a:expr, $b:expr, $($rest_a:expr, $rest_b:expr),+) => {
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match ($a).partial_cmp(&$b) {
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@ -1,6 +1,7 @@
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// Ensure the asm for array comparisons is properly optimized.
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//@ compile-flags: -C opt-level=2
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//@ needs-deterministic-layouts (checks depend on tuple layout)
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#![crate_type = "lib"]
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@ -19,13 +20,55 @@ pub fn compare() -> bool {
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}
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// CHECK-LABEL: @array_of_tuple_le
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// CHECK: call{{.+}}i8 @llvm.scmp.i8.i16
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// CHECK: call{{.+}}i8 @llvm.ucmp.i8.i16
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// CHECK: call{{.+}}i8 @llvm.scmp.i8.i16
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// CHECK: call{{.+}}i8 @llvm.ucmp.i8.i16
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// CHECK: %[[RET:.+]] = icmp slt i8 {{.+}}, 1
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// CHECK: ret i8 %[[RET]]
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#[no_mangle]
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pub fn array_of_tuple_le(a: &[(i16, u16); 2], b: &[(i16, u16); 2]) -> bool {
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// Ensure that, after all the optimizations have run, the happy path just checks
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// `eq` on each corresponding pair and moves onto the next one if it is.
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// Then there's a dedup'd comparison for the place that's different.
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// (As opposed to, say, running a full `[su]cmp` as part of checking equality.)
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// This is written quite specifically because different library code was triggering
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// <https://github.com/llvm/llvm-project/issues/132678> along the way, so this
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// has enough checks to make sure that's not happening. It doesn't need to be
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// *exactly* this IR, but be careful if you ever need to update these checks.
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// CHECK: start:
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// CHECK: %[[A00:.+]] = load i16, ptr %a
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// CHECK: %[[B00:.+]] = load i16, ptr %b
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// CHECK-NOT: cmp
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// CHECK: %[[EQ00:.+]] = icmp eq i16 %[[A00]], %[[B00]]
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// CHECK-NEXT: br i1 %[[EQ00]], label %[[L01:.+]], label %[[EXIT_S:.+]]
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// CHECK: [[L01]]:
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// CHECK: %[[PA01:.+]] = getelementptr{{.+}}i8, ptr %a, {{i32|i64}} 2
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// CHECK: %[[PB01:.+]] = getelementptr{{.+}}i8, ptr %b, {{i32|i64}} 2
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// CHECK: %[[A01:.+]] = load i16, ptr %[[PA01]]
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// CHECK: %[[B01:.+]] = load i16, ptr %[[PB01]]
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// CHECK-NOT: cmp
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// CHECK: %[[EQ01:.+]] = icmp eq i16 %[[A01]], %[[B01]]
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// CHECK-NEXT: br i1 %[[EQ01]], label %[[L10:.+]], label %[[EXIT_U:.+]]
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// CHECK: [[L10]]:
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// CHECK: %[[PA10:.+]] = getelementptr{{.+}}i8, ptr %a, {{i32|i64}} 4
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// CHECK: %[[PB10:.+]] = getelementptr{{.+}}i8, ptr %b, {{i32|i64}} 4
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// CHECK: %[[A10:.+]] = load i16, ptr %[[PA10]]
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// CHECK: %[[B10:.+]] = load i16, ptr %[[PB10]]
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// CHECK-NOT: cmp
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// CHECK: %[[EQ10:.+]] = icmp eq i16 %[[A10]], %[[B10]]
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// CHECK-NEXT: br i1 %[[EQ10]], label %[[L11:.+]], label %[[EXIT_S]]
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// CHECK: [[L11]]:
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// CHECK: %[[PA11:.+]] = getelementptr{{.+}}i8, ptr %a, {{i32|i64}} 6
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// CHECK: %[[PB11:.+]] = getelementptr{{.+}}i8, ptr %b, {{i32|i64}} 6
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// CHECK: %[[A11:.+]] = load i16, ptr %[[PA11]]
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// CHECK: %[[B11:.+]] = load i16, ptr %[[PB11]]
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// CHECK-NOT: cmp
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// CHECK: %[[EQ11:.+]] = icmp eq i16 %[[A11]], %[[B11]]
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// CHECK-NEXT: br i1 %[[EQ11]], label %[[DONE:.+]], label %[[EXIT_U]]
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// CHECK: [[DONE]]:
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// CHECK: %[[RET:.+]] = phi i1 [ %{{.+}}, %[[EXIT_S]] ], [ %{{.+}}, %[[EXIT_U]] ], [ true, %[[L11]] ]
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// CHECK: ret i1 %[[RET]]
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a <= b
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}
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