Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 317 insertions, 0 deletions

diff --git a/vendor/memchr/src/arch/generic/packedpair.rs b/vendor/memchr/src/arch/generic/packedpair.rs
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+++ b/vendor/memchr/src/arch/generic/packedpair.rs
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+/*!
+Generic crate-internal routines for the "packed pair" SIMD algorithm.
+
+The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
+difference is that it (by default) uses a background distribution of byte
+frequencies to heuristically select the pair of bytes to search for.
+
+[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
+*/
+
+use crate::{
+    arch::all::{is_equal_raw, packedpair::Pair},
+    ext::Pointer,
+    vector::{MoveMask, Vector},
+};
+
+/// A generic architecture dependent "packed pair" finder.
+///
+/// This finder picks two bytes that it believes have high predictive power
+/// for indicating an overall match of a needle. Depending on whether
+/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
+/// where the needle matches or could match. In the prefilter case, candidates
+/// are reported whenever the [`Pair`] of bytes given matches.
+///
+/// This is architecture dependent because it uses specific vector operations
+/// to look for occurrences of the pair of bytes.
+///
+/// This type is not meant to be exported and is instead meant to be used as
+/// the implementation for architecture specific facades. Why? Because it's a
+/// bit of a quirky API that requires `inline(always)` annotations. And pretty
+/// much everything has safety obligations due (at least) to the caller needing
+/// to inline calls into routines marked with
+/// `#[target_feature(enable = "...")]`.
+#[derive(Clone, Copy, Debug)]
+pub(crate) struct Finder<V> {
+    pair: Pair,
+    v1: V,
+    v2: V,
+    min_haystack_len: usize,
+}
+
+impl<V: Vector> Finder<V> {
+    /// Create a new pair searcher. The searcher returned can either report
+    /// exact matches of `needle` or act as a prefilter and report candidate
+    /// positions of `needle`.
+    ///
+    /// # Safety
+    ///
+    /// Callers must ensure that whatever vector type this routine is called
+    /// with is supported by the current environment.
+    ///
+    /// Callers must also ensure that `needle.len() >= 2`.
+    #[inline(always)]
+    pub(crate) unsafe fn new(needle: &[u8], pair: Pair) -> Finder<V> {
+        let max_index = pair.index1().max(pair.index2());
+        let min_haystack_len =
+            core::cmp::max(needle.len(), usize::from(max_index) + V::BYTES);
+        let v1 = V::splat(needle[usize::from(pair.index1())]);
+        let v2 = V::splat(needle[usize::from(pair.index2())]);
+        Finder { pair, v1, v2, min_haystack_len }
+    }
+
+    /// Searches the given haystack for the given needle. The needle given
+    /// should be the same as the needle that this finder was initialized
+    /// with.
+    ///
+    /// # Panics
+    ///
+    /// When `haystack.len()` is less than [`Finder::min_haystack_len`].
+    ///
+    /// # Safety
+    ///
+    /// Since this is meant to be used with vector functions, callers need to
+    /// specialize this inside of a function with a `target_feature` attribute.
+    /// Therefore, callers must ensure that whatever target feature is being
+    /// used supports the vector functions that this function is specialized
+    /// for. (For the specific vector functions used, see the Vector trait
+    /// implementations.)
+    #[inline(always)]
+    pub(crate) unsafe fn find(
+        &self,
+        haystack: &[u8],
+        needle: &[u8],
+    ) -> Option<usize> {
+        assert!(
+            haystack.len() >= self.min_haystack_len,
+            "haystack too small, should be at least {} but got {}",
+            self.min_haystack_len,
+            haystack.len(),
+        );
+
+        let all = V::Mask::all_zeros_except_least_significant(0);
+        let start = haystack.as_ptr();
+        let end = start.add(haystack.len());
+        let max = end.sub(self.min_haystack_len);
+        let mut cur = start;
+
+        // N.B. I did experiment with unrolling the loop to deal with size(V)
+        // bytes at a time and 2*size(V) bytes at a time. The double unroll
+        // was marginally faster while the quadruple unroll was unambiguously
+        // slower. In the end, I decided the complexity from unrolling wasn't
+        // worth it. I used the memmem/krate/prebuilt/huge-en/ benchmarks to
+        // compare.
+        while cur <= max {
+            if let Some(chunki) = self.find_in_chunk(needle, cur, end, all) {
+                return Some(matched(start, cur, chunki));
+            }
+            cur = cur.add(V::BYTES);
+        }
+        if cur < end {
+            let remaining = end.distance(cur);
+            debug_assert!(
+                remaining < self.min_haystack_len,
+                "remaining bytes should be smaller than the minimum haystack \
+                 length of {}, but there are {} bytes remaining",
+                self.min_haystack_len,
+                remaining,
+            );
+            if remaining < needle.len() {
+                return None;
+            }
+            debug_assert!(
+                max < cur,
+                "after main loop, cur should have exceeded max",
+            );
+            let overlap = cur.distance(max);
+            debug_assert!(
+                overlap > 0,
+                "overlap ({}) must always be non-zero",
+                overlap,
+            );
+            debug_assert!(
+                overlap < V::BYTES,
+                "overlap ({}) cannot possibly be >= than a vector ({})",
+                overlap,
+                V::BYTES,
+            );
+            // The mask has all of its bits set except for the first N least
+            // significant bits, where N=overlap. This way, any matches that
+            // occur in find_in_chunk within the overlap are automatically
+            // ignored.
+            let mask = V::Mask::all_zeros_except_least_significant(overlap);
+            cur = max;
+            let m = self.find_in_chunk(needle, cur, end, mask);
+            if let Some(chunki) = m {
+                return Some(matched(start, cur, chunki));
+            }
+        }
+        None
+    }
+
+    /// Searches the given haystack for offsets that represent candidate
+    /// matches of the `needle` given to this finder's constructor. The offsets
+    /// returned, if they are a match, correspond to the starting offset of
+    /// `needle` in the given `haystack`.
+    ///
+    /// # Panics
+    ///
+    /// When `haystack.len()` is less than [`Finder::min_haystack_len`].
+    ///
+    /// # Safety
+    ///
+    /// Since this is meant to be used with vector functions, callers need to
+    /// specialize this inside of a function with a `target_feature` attribute.
+    /// Therefore, callers must ensure that whatever target feature is being
+    /// used supports the vector functions that this function is specialized
+    /// for. (For the specific vector functions used, see the Vector trait
+    /// implementations.)
+    #[inline(always)]
+    pub(crate) unsafe fn find_prefilter(
+        &self,
+        haystack: &[u8],
+    ) -> Option<usize> {
+        assert!(
+            haystack.len() >= self.min_haystack_len,
+            "haystack too small, should be at least {} but got {}",
+            self.min_haystack_len,
+            haystack.len(),
+        );
+
+        let start = haystack.as_ptr();
+        let end = start.add(haystack.len());
+        let max = end.sub(self.min_haystack_len);
+        let mut cur = start;
+
+        // N.B. I did experiment with unrolling the loop to deal with size(V)
+        // bytes at a time and 2*size(V) bytes at a time. The double unroll
+        // was marginally faster while the quadruple unroll was unambiguously
+        // slower. In the end, I decided the complexity from unrolling wasn't
+        // worth it. I used the memmem/krate/prebuilt/huge-en/ benchmarks to
+        // compare.
+        while cur <= max {
+            if let Some(chunki) = self.find_prefilter_in_chunk(cur) {
+                return Some(matched(start, cur, chunki));
+            }
+            cur = cur.add(V::BYTES);
+        }
+        if cur < end {
+            // This routine immediately quits if a candidate match is found.
+            // That means that if we're here, no candidate matches have been
+            // found at or before 'ptr'. Thus, we don't need to mask anything
+            // out even though we might technically search part of the haystack
+            // that we've already searched (because we know it can't match).
+            cur = max;
+            if let Some(chunki) = self.find_prefilter_in_chunk(cur) {
+                return Some(matched(start, cur, chunki));
+            }
+        }
+        None
+    }
+
+    /// Search for an occurrence of our byte pair from the needle in the chunk
+    /// pointed to by cur, with the end of the haystack pointed to by end.
+    /// When an occurrence is found, memcmp is run to check if a match occurs
+    /// at the corresponding position.
+    ///
+    /// `mask` should have bits set corresponding the positions in the chunk
+    /// in which matches are considered. This is only used for the last vector
+    /// load where the beginning of the vector might have overlapped with the
+    /// last load in the main loop. The mask lets us avoid visiting positions
+    /// that have already been discarded as matches.
+    ///
+    /// # Safety
+    ///
+    /// It must be safe to do an unaligned read of size(V) bytes starting at
+    /// both (cur + self.index1) and (cur + self.index2). It must also be safe
+    /// to do unaligned loads on cur up to (end - needle.len()).
+    #[inline(always)]
+    unsafe fn find_in_chunk(
+        &self,
+        needle: &[u8],
+        cur: *const u8,
+        end: *const u8,
+        mask: V::Mask,
+    ) -> Option<usize> {
+        let index1 = usize::from(self.pair.index1());
+        let index2 = usize::from(self.pair.index2());
+        let chunk1 = V::load_unaligned(cur.add(index1));
+        let chunk2 = V::load_unaligned(cur.add(index2));
+        let eq1 = chunk1.cmpeq(self.v1);
+        let eq2 = chunk2.cmpeq(self.v2);
+
+        let mut offsets = eq1.and(eq2).movemask().and(mask);
+        while offsets.has_non_zero() {
+            let offset = offsets.first_offset();
+            let cur = cur.add(offset);
+            if end.sub(needle.len()) < cur {
+                return None;
+            }
+            if is_equal_raw(needle.as_ptr(), cur, needle.len()) {
+                return Some(offset);
+            }
+            offsets = offsets.clear_least_significant_bit();
+        }
+        None
+    }
+
+    /// Search for an occurrence of our byte pair from the needle in the chunk
+    /// pointed to by cur, with the end of the haystack pointed to by end.
+    /// When an occurrence is found, memcmp is run to check if a match occurs
+    /// at the corresponding position.
+    ///
+    /// # Safety
+    ///
+    /// It must be safe to do an unaligned read of size(V) bytes starting at
+    /// both (cur + self.index1) and (cur + self.index2). It must also be safe
+    /// to do unaligned reads on cur up to (end - needle.len()).
+    #[inline(always)]
+    unsafe fn find_prefilter_in_chunk(&self, cur: *const u8) -> Option<usize> {
+        let index1 = usize::from(self.pair.index1());
+        let index2 = usize::from(self.pair.index2());
+        let chunk1 = V::load_unaligned(cur.add(index1));
+        let chunk2 = V::load_unaligned(cur.add(index2));
+        let eq1 = chunk1.cmpeq(self.v1);
+        let eq2 = chunk2.cmpeq(self.v2);
+
+        let offsets = eq1.and(eq2).movemask();
+        if !offsets.has_non_zero() {
+            return None;
+        }
+        Some(offsets.first_offset())
+    }
+
+    /// Returns the pair of offsets (into the needle) used to check as a
+    /// predicate before confirming whether a needle exists at a particular
+    /// position.
+    #[inline]
+    pub(crate) fn pair(&self) -> &Pair {
+        &self.pair
+    }
+
+    /// Returns the minimum haystack length that this `Finder` can search.
+    ///
+    /// Providing a haystack to this `Finder` shorter than this length is
+    /// guaranteed to result in a panic.
+    #[inline(always)]
+    pub(crate) fn min_haystack_len(&self) -> usize {
+        self.min_haystack_len
+    }
+}
+
+/// Accepts a chunk-relative offset and returns a haystack relative offset.
+///
+/// This used to be marked `#[cold]` and `#[inline(never)]`, but I couldn't
+/// observe a consistent measureable difference between that and just inlining
+/// it. So we go with inlining it.
+///
+/// # Safety
+///
+/// Same at `ptr::offset_from` in addition to `cur >= start`.
+#[inline(always)]
+unsafe fn matched(start: *const u8, cur: *const u8, chunki: usize) -> usize {
+    cur.distance(start) + chunki
+}
+
+// If you're looking for tests, those are run for each instantiation of the
+// above code. So for example, see arch::x86_64::sse2::packedpair.