optimization: Eliminate Cased table

`Cased` is a derived property - it is the union of the `Lowercase`
property, the `Uppercase` property, and the `Titlecase_Letter` general
categories. We already have lookup tables for `Lowercase` and
`Uppercase`, and `Titlecase_Letter` is very small. So instead of
duplicating a lookup table for `Cased`, just test each of those
properties in turn.

This probably will be slower than the old approach, but it is not a
public API: it is only used in `string::to_lower` when deciding when a
Greek "sigma" should be mapped to `ς` or to `σ`. This is a very rare
case, so should not be performance sensitive.

Author: Kmeakin

library/core/src/char/methods.rs

@@ -985,7 +985,11 @@ impl char {
     #[doc(hidden)]
     #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
     pub fn is_cased(self) -> bool {
-        if self.is_ascii() { self.is_ascii_alphabetic() } else { unicode::Cased(self) }
+        if self.is_ascii() {
+            self.is_ascii_alphabetic()
+        } else {
+            unicode::Lowercase(self) || unicode::Uppercase(self) || unicode::Lt(self)
+        }
     }
 
     /// Returns `true` if this `char` has the `Case_Ignorable` property.

library/core/src/unicode/mod.rs

@@ -5,13 +5,13 @@
 // for use in alloc, not re-exported in std.
 #[rustfmt::skip]
 pub use unicode_data::case_ignorable::lookup as Case_Ignorable;
-pub use unicode_data::cased::lookup as Cased;
 pub use unicode_data::conversions;
 
 #[rustfmt::skip]
 pub(crate) use unicode_data::alphabetic::lookup as Alphabetic;
 pub(crate) use unicode_data::grapheme_extend::lookup as Grapheme_Extend;
 pub(crate) use unicode_data::lowercase::lookup as Lowercase;
+pub(crate) use unicode_data::lt::lookup as Lt;
 pub(crate) use unicode_data::n::lookup as N;
 pub(crate) use unicode_data::uppercase::lookup as Uppercase;
 pub(crate) use unicode_data::white_space::lookup as White_Space;

library/core/src/unicode/unicode_data.rs

@@ -1,15 +1,15 @@
 //! This file is generated by `./x run src/tools/unicode-table-generator`; do not edit manually!
 // Alphabetic      :  1723 bytes, 147369 codepoints in 759 ranges (U+0000AA - U+03347A) using skiplist
 // Case_Ignorable  :  1063 bytes,   2789 codepoints in 459 ranges (U+0000A8 - U+0E01F0) using skiplist
-// Cased           :   401 bytes,   4580 codepoints in 156 ranges (U+0000AA - U+01F18A) using skiplist
 // Grapheme_Extend :   899 bytes,   2232 codepoints in 383 ranges (U+000300 - U+0E01F0) using skiplist
 // Lowercase       :   943 bytes,   2569 codepoints in 676 ranges (U+0000AA - U+01E944) using bitset
+// Lt              :    33 bytes,     31 codepoints in  10 ranges (U+0001C5 - U+001FFD) using skiplist
 // N               :   463 bytes,   1914 codepoints in 145 ranges (U+0000B2 - U+01FBFA) using skiplist
 // Uppercase       :   799 bytes,   1980 codepoints in 659 ranges (U+0000C0 - U+01F18A) using bitset
 // White_Space     :   256 bytes,     19 codepoints in   8 ranges (U+000085 - U+003001) using cascading
 // to_lower        : 11708 bytes
 // to_upper        : 13656 bytes
-// Total           : 31911 bytes
+// Total           : 31543 bytes
 
 use super::rt::*;
 
@@ -253,70 +253,6 @@ pub mod case_ignorable {
     }
 }
 
-pub mod cased {
-    use super::ShortOffsetRunHeader;
-
-    static SHORT_OFFSET_RUNS: [ShortOffsetRunHeader; 22] = [
-        ShortOffsetRunHeader::new(0, 4256),
-        ShortOffsetRunHeader::new(51, 5024),
-        ShortOffsetRunHeader::new(61, 7296),
-        ShortOffsetRunHeader::new(65, 7958),
-        ShortOffsetRunHeader::new(74, 9398),
-        ShortOffsetRunHeader::new(149, 11264),
-        ShortOffsetRunHeader::new(151, 42560),
-        ShortOffsetRunHeader::new(163, 43824),
-        ShortOffsetRunHeader::new(177, 64256),
-        ShortOffsetRunHeader::new(183, 65313),
-        ShortOffsetRunHeader::new(187, 66560),
-        ShortOffsetRunHeader::new(191, 67456),
-        ShortOffsetRunHeader::new(213, 68736),
-        ShortOffsetRunHeader::new(221, 71840),
-        ShortOffsetRunHeader::new(229, 93760),
-        ShortOffsetRunHeader::new(231, 119808),
-        ShortOffsetRunHeader::new(237, 120486),
-        ShortOffsetRunHeader::new(274, 122624),
-        ShortOffsetRunHeader::new(297, 122928),
-        ShortOffsetRunHeader::new(303, 125184),
-        ShortOffsetRunHeader::new(305, 127280),
-        ShortOffsetRunHeader::new(307, 1241482),
-    ];
-    static OFFSETS: [u8; 313] = [
-        170, 1, 10, 1, 4, 1, 5, 23, 1, 31, 1, 195, 1, 4, 4, 208, 2, 35, 7, 2, 30, 5, 96, 1, 42, 4,
-        2, 2, 2, 4, 1, 1, 6, 1, 1, 3, 1, 1, 1, 20, 1, 83, 1, 139, 8, 166, 1, 38, 9, 41, 0, 38, 1,
-        1, 5, 1, 2, 43, 1, 4, 0, 86, 2, 6, 0, 11, 5, 43, 2, 3, 64, 192, 64, 0, 2, 6, 2, 38, 2, 6,
-        2, 8, 1, 1, 1, 1, 1, 1, 1, 31, 2, 53, 1, 7, 1, 1, 3, 3, 1, 7, 3, 4, 2, 6, 4, 13, 5, 3, 1,
-        7, 116, 1, 13, 1, 16, 13, 101, 1, 4, 1, 2, 10, 1, 1, 3, 5, 6, 1, 1, 1, 1, 1, 1, 4, 1, 6, 4,
-        1, 2, 4, 5, 5, 4, 1, 17, 32, 3, 2, 0, 52, 0, 229, 6, 4, 3, 2, 12, 38, 1, 1, 5, 1, 0, 46,
-        18, 30, 132, 102, 3, 4, 1, 77, 20, 6, 1, 3, 0, 43, 1, 14, 6, 80, 0, 7, 12, 5, 0, 26, 6, 26,
-        0, 80, 96, 36, 4, 36, 116, 11, 1, 15, 1, 7, 1, 2, 1, 11, 1, 15, 1, 7, 1, 2, 0, 1, 2, 3, 1,
-        42, 1, 9, 0, 51, 13, 51, 93, 22, 10, 22, 0, 64, 0, 64, 32, 25, 2, 25, 0, 85, 1, 71, 1, 2,
-        2, 1, 2, 2, 2, 4, 1, 12, 1, 1, 1, 7, 1, 65, 1, 4, 2, 8, 1, 7, 1, 28, 1, 4, 1, 5, 1, 1, 3,
-        7, 1, 0, 2, 25, 1, 25, 1, 31, 1, 25, 1, 31, 1, 25, 1, 31, 1, 25, 1, 31, 1, 25, 1, 8, 0, 10,
-        1, 20, 6, 6, 0, 62, 0, 68, 0, 26, 6, 26, 6, 26, 0,
-    ];
-
-    #[inline]
-    pub fn lookup(c: char) -> bool {
-        debug_assert!(!c.is_ascii());
-        (c as u32) >= 0xaa && lookup_slow(c)
-    }
-
-    #[inline(never)]
-    fn lookup_slow(c: char) -> bool {
-        const {
-            assert!(SHORT_OFFSET_RUNS.last().unwrap().0 > char::MAX as u32);
-            let mut i = 0;
-            while i < SHORT_OFFSET_RUNS.len() {
-                assert!(SHORT_OFFSET_RUNS[i].start_index() < OFFSETS.len());
-                i += 1;
-            }
-        }
-        // SAFETY: We just ensured the last element of `SHORT_OFFSET_RUNS` is greater than `std::char::MAX`
-        // and the start indices of all elements in `SHORT_OFFSET_RUNS` are smaller than `OFFSETS.len()`.
-        unsafe { super::skip_search(c, &SHORT_OFFSET_RUNS, &OFFSETS) }
-    }
-}
-
 pub mod grapheme_extend {
     use super::ShortOffsetRunHeader;
 
@@ -535,6 +471,38 @@ pub mod lowercase {
     }
 }
 
+pub mod lt {
+    use super::ShortOffsetRunHeader;
+
+    static SHORT_OFFSET_RUNS: [ShortOffsetRunHeader; 3] = [
+        ShortOffsetRunHeader::new(0, 453),
+        ShortOffsetRunHeader::new(1, 8072),
+        ShortOffsetRunHeader::new(9, 1122301),
+    ];
+    static OFFSETS: [u8; 21] = [0, 1, 2, 1, 2, 1, 38, 1, 0, 8, 8, 8, 8, 8, 12, 1, 15, 1, 47, 1, 0];
+
+    #[inline]
+    pub fn lookup(c: char) -> bool {
+        debug_assert!(!c.is_ascii());
+        (c as u32) >= 0x1c5 && lookup_slow(c)
+    }
+
+    #[inline(never)]
+    fn lookup_slow(c: char) -> bool {
+        const {
+            assert!(SHORT_OFFSET_RUNS.last().unwrap().0 > char::MAX as u32);
+            let mut i = 0;
+            while i < SHORT_OFFSET_RUNS.len() {
+                assert!(SHORT_OFFSET_RUNS[i].start_index() < OFFSETS.len());
+                i += 1;
+            }
+        }
+        // SAFETY: We just ensured the last element of `SHORT_OFFSET_RUNS` is greater than `std::char::MAX`
+        // and the start indices of all elements in `SHORT_OFFSET_RUNS` are smaller than `OFFSETS.len()`.
+        unsafe { super::skip_search(c, &SHORT_OFFSET_RUNS, &OFFSETS) }
+    }
+}
+
 pub mod n {
     use super::ShortOffsetRunHeader;
 

library/coretests/tests/unicode/test_data.rs

@@ -392,60 +392,6 @@ pub(super) static CASE_IGNORABLE: &[RangeInclusive<char>; 459] = &[
     '\u{e0100}'..='\u{e01ef}',
 ];
 
-#[rustfmt::skip]
-pub(super) static CASED: &[RangeInclusive<char>; 156] = &[
-    '\u{aa}'..='\u{aa}', '\u{b5}'..='\u{b5}', '\u{ba}'..='\u{ba}', '\u{c0}'..='\u{d6}',
-    '\u{d8}'..='\u{f6}', '\u{f8}'..='\u{1ba}', '\u{1bc}'..='\u{1bf}', '\u{1c4}'..='\u{293}',
-    '\u{296}'..='\u{2b8}', '\u{2c0}'..='\u{2c1}', '\u{2e0}'..='\u{2e4}', '\u{345}'..='\u{345}',
-    '\u{370}'..='\u{373}', '\u{376}'..='\u{377}', '\u{37a}'..='\u{37d}', '\u{37f}'..='\u{37f}',
-    '\u{386}'..='\u{386}', '\u{388}'..='\u{38a}', '\u{38c}'..='\u{38c}', '\u{38e}'..='\u{3a1}',
-    '\u{3a3}'..='\u{3f5}', '\u{3f7}'..='\u{481}', '\u{48a}'..='\u{52f}', '\u{531}'..='\u{556}',
-    '\u{560}'..='\u{588}', '\u{10a0}'..='\u{10c5}', '\u{10c7}'..='\u{10c7}',
-    '\u{10cd}'..='\u{10cd}', '\u{10d0}'..='\u{10fa}', '\u{10fc}'..='\u{10ff}',
-    '\u{13a0}'..='\u{13f5}', '\u{13f8}'..='\u{13fd}', '\u{1c80}'..='\u{1c8a}',
-    '\u{1c90}'..='\u{1cba}', '\u{1cbd}'..='\u{1cbf}', '\u{1d00}'..='\u{1dbf}',
-    '\u{1e00}'..='\u{1f15}', '\u{1f18}'..='\u{1f1d}', '\u{1f20}'..='\u{1f45}',
-    '\u{1f48}'..='\u{1f4d}', '\u{1f50}'..='\u{1f57}', '\u{1f59}'..='\u{1f59}',
-    '\u{1f5b}'..='\u{1f5b}', '\u{1f5d}'..='\u{1f5d}', '\u{1f5f}'..='\u{1f7d}',
-    '\u{1f80}'..='\u{1fb4}', '\u{1fb6}'..='\u{1fbc}', '\u{1fbe}'..='\u{1fbe}',
-    '\u{1fc2}'..='\u{1fc4}', '\u{1fc6}'..='\u{1fcc}', '\u{1fd0}'..='\u{1fd3}',
-    '\u{1fd6}'..='\u{1fdb}', '\u{1fe0}'..='\u{1fec}', '\u{1ff2}'..='\u{1ff4}',
-    '\u{1ff6}'..='\u{1ffc}', '\u{2071}'..='\u{2071}', '\u{207f}'..='\u{207f}',
-    '\u{2090}'..='\u{209c}', '\u{2102}'..='\u{2102}', '\u{2107}'..='\u{2107}',
-    '\u{210a}'..='\u{2113}', '\u{2115}'..='\u{2115}', '\u{2119}'..='\u{211d}',
-    '\u{2124}'..='\u{2124}', '\u{2126}'..='\u{2126}', '\u{2128}'..='\u{2128}',
-    '\u{212a}'..='\u{212d}', '\u{212f}'..='\u{2134}', '\u{2139}'..='\u{2139}',
-    '\u{213c}'..='\u{213f}', '\u{2145}'..='\u{2149}', '\u{214e}'..='\u{214e}',
-    '\u{2160}'..='\u{217f}', '\u{2183}'..='\u{2184}', '\u{24b6}'..='\u{24e9}',
-    '\u{2c00}'..='\u{2ce4}', '\u{2ceb}'..='\u{2cee}', '\u{2cf2}'..='\u{2cf3}',
-    '\u{2d00}'..='\u{2d25}', '\u{2d27}'..='\u{2d27}', '\u{2d2d}'..='\u{2d2d}',
-    '\u{a640}'..='\u{a66d}', '\u{a680}'..='\u{a69d}', '\u{a722}'..='\u{a787}',
-    '\u{a78b}'..='\u{a78e}', '\u{a790}'..='\u{a7dc}', '\u{a7f1}'..='\u{a7f6}',
-    '\u{a7f8}'..='\u{a7fa}', '\u{ab30}'..='\u{ab5a}', '\u{ab5c}'..='\u{ab69}',
-    '\u{ab70}'..='\u{abbf}', '\u{fb00}'..='\u{fb06}', '\u{fb13}'..='\u{fb17}',
-    '\u{ff21}'..='\u{ff3a}', '\u{ff41}'..='\u{ff5a}', '\u{10400}'..='\u{1044f}',
-    '\u{104b0}'..='\u{104d3}', '\u{104d8}'..='\u{104fb}', '\u{10570}'..='\u{1057a}',
-    '\u{1057c}'..='\u{1058a}', '\u{1058c}'..='\u{10592}', '\u{10594}'..='\u{10595}',
-    '\u{10597}'..='\u{105a1}', '\u{105a3}'..='\u{105b1}', '\u{105b3}'..='\u{105b9}',
-    '\u{105bb}'..='\u{105bc}', '\u{10780}'..='\u{10780}', '\u{10783}'..='\u{10785}',
-    '\u{10787}'..='\u{107b0}', '\u{107b2}'..='\u{107ba}', '\u{10c80}'..='\u{10cb2}',
-    '\u{10cc0}'..='\u{10cf2}', '\u{10d50}'..='\u{10d65}', '\u{10d70}'..='\u{10d85}',
-    '\u{118a0}'..='\u{118df}', '\u{16e40}'..='\u{16e7f}', '\u{16ea0}'..='\u{16eb8}',
-    '\u{16ebb}'..='\u{16ed3}', '\u{1d400}'..='\u{1d454}', '\u{1d456}'..='\u{1d49c}',
-    '\u{1d49e}'..='\u{1d49f}', '\u{1d4a2}'..='\u{1d4a2}', '\u{1d4a5}'..='\u{1d4a6}',
-    '\u{1d4a9}'..='\u{1d4ac}', '\u{1d4ae}'..='\u{1d4b9}', '\u{1d4bb}'..='\u{1d4bb}',
-    '\u{1d4bd}'..='\u{1d4c3}', '\u{1d4c5}'..='\u{1d505}', '\u{1d507}'..='\u{1d50a}',
-    '\u{1d50d}'..='\u{1d514}', '\u{1d516}'..='\u{1d51c}', '\u{1d51e}'..='\u{1d539}',
-    '\u{1d53b}'..='\u{1d53e}', '\u{1d540}'..='\u{1d544}', '\u{1d546}'..='\u{1d546}',
-    '\u{1d54a}'..='\u{1d550}', '\u{1d552}'..='\u{1d6a5}', '\u{1d6a8}'..='\u{1d6c0}',
-    '\u{1d6c2}'..='\u{1d6da}', '\u{1d6dc}'..='\u{1d6fa}', '\u{1d6fc}'..='\u{1d714}',
-    '\u{1d716}'..='\u{1d734}', '\u{1d736}'..='\u{1d74e}', '\u{1d750}'..='\u{1d76e}',
-    '\u{1d770}'..='\u{1d788}', '\u{1d78a}'..='\u{1d7a8}', '\u{1d7aa}'..='\u{1d7c2}',
-    '\u{1d7c4}'..='\u{1d7cb}', '\u{1df00}'..='\u{1df09}', '\u{1df0b}'..='\u{1df1e}',
-    '\u{1df25}'..='\u{1df2a}', '\u{1e030}'..='\u{1e06d}', '\u{1e900}'..='\u{1e943}',
-    '\u{1f130}'..='\u{1f149}', '\u{1f150}'..='\u{1f169}', '\u{1f170}'..='\u{1f189}',
-];
-
 #[rustfmt::skip]
 pub(super) static GRAPHEME_EXTEND: &[RangeInclusive<char>; 383] = &[
     '\u{300}'..='\u{36f}', '\u{483}'..='\u{489}', '\u{591}'..='\u{5bd}', '\u{5bf}'..='\u{5bf}',
@@ -776,6 +722,13 @@ pub(super) static LOWERCASE: &[RangeInclusive<char>; 676] = &[
     '\u{1e030}'..='\u{1e06d}', '\u{1e922}'..='\u{1e943}',
 ];
 
+#[rustfmt::skip]
+pub(super) static LT: &[RangeInclusive<char>; 10] = &[
+    '\u{1c5}'..='\u{1c5}', '\u{1c8}'..='\u{1c8}', '\u{1cb}'..='\u{1cb}', '\u{1f2}'..='\u{1f2}',
+    '\u{1f88}'..='\u{1f8f}', '\u{1f98}'..='\u{1f9f}', '\u{1fa8}'..='\u{1faf}',
+    '\u{1fbc}'..='\u{1fbc}', '\u{1fcc}'..='\u{1fcc}', '\u{1ffc}'..='\u{1ffc}',
+];
+
 #[rustfmt::skip]
 pub(super) static N: &[RangeInclusive<char>; 145] = &[
     '\u{b2}'..='\u{b3}', '\u{b9}'..='\u{b9}', '\u{bc}'..='\u{be}', '\u{660}'..='\u{669}',

src/tools/unicode-table-generator/src/main.rs

@@ -90,7 +90,7 @@ static PROPERTIES: &[&str] = &[
     "Alphabetic",
     "Lowercase",
     "Uppercase",
-    "Cased",
+    "Lt",
     "Case_Ignorable",
     "Grapheme_Extend",
     "White_Space",