Introduce Overflow & Displacement tracking.

Cargo.toml

@@ -52,20 +52,38 @@ default = ["ahash", "inline-more", "allocator-api2"]
 nightly = ["allocator-api2?/nightly", "bumpalo/allocator_api"]
 
 rustc-internal-api = []
+
 rustc-dep-of-std = [
     "nightly",
     "core",
     "compiler_builtins",
     "alloc",
     "rustc-internal-api",
 ]
+
 raw = []
 
 # Enables usage of `#[inline]` on far more functions than by default in this
 # crate. This may lead to a performance increase but often comes at a compile
 # time cost.
 inline-more = []
 
+# If no overflow-tracker is selected, then the default is none.
+#
+# A single tracker can be selected at any time, selecting two or more is an error.
+
+# Bloom filter overflow-tracker, ala boost::unordered_flat_map.
+overflow-tracker-bloom-1-u8 = []
+
+# Bloom filter overflow-tracker, with more accuracy.
+overflow-tracker-bloom-1-u16 = []
+
+# Counter overflow-tracker, ala F14.
+overflow-tracker-counter-u8 = []
+
+# Hybrid overflow-tracker, mixing a counter and a bloom filter.
+overflow-tracker-hybrid = []
+
 [package.metadata.docs.rs]
 features = ["nightly", "rayon", "serde", "raw"]
 rustdoc-args = ["--generate-link-to-definition"]

src/raw/bitmask.rs

@@ -54,21 +54,6 @@ impl BitMask {
         }
     }
 
-    /// Returns the number of trailing zeroes in the `BitMask`.
-    #[inline]
-    pub(crate) fn trailing_zeros(self) -> usize {
-        // ARM doesn't have a trailing_zeroes instruction, and instead uses
-        // reverse_bits (RBIT) + leading_zeroes (CLZ). However older ARM
-        // versions (pre-ARMv7) don't have RBIT and need to emulate it
-        // instead. Since we only have 1 bit set in each byte on ARM, we can
-        // use swap_bytes (REV) + leading_zeroes instead.
-        if cfg!(target_arch = "arm") && BITMASK_STRIDE % 8 == 0 {
-            self.0.swap_bytes().leading_zeros() as usize / BITMASK_STRIDE
-        } else {
-            self.0.trailing_zeros() as usize / BITMASK_STRIDE
-        }
-    }
-
     /// Same as above but takes a `NonZeroBitMaskWord`.
     #[inline]
     fn nonzero_trailing_zeros(nonzero: NonZeroBitMaskWord) -> usize {
@@ -80,12 +65,6 @@ impl BitMask {
             nonzero.trailing_zeros() as usize / BITMASK_STRIDE
         }
     }
-
-    /// Returns the number of leading zeroes in the `BitMask`.
-    #[inline]
-    pub(crate) fn leading_zeros(self) -> usize {
-        self.0.leading_zeros() as usize / BITMASK_STRIDE
-    }
 }
 
 impl IntoIterator for BitMask {

src/raw/generic.rs

@@ -69,13 +69,6 @@ impl Group {
         &ALIGNED_BYTES.bytes
     }
 
-    /// Loads a group of bytes starting at the given address.
-    #[inline]
-    #[allow(clippy::cast_ptr_alignment)] // unaligned load
-    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
-        Group(ptr::read_unaligned(ptr.cast()))
-    }
-
     /// Loads a group of bytes starting at the given address, which must be
     /// aligned to `mem::align_of::<Group>()`.
     #[inline]