Add a right shift mapping

This saves less bytes - by far - and is likely not the best operator to choose.
But for now, it works -- a better choice may arise later.

Alphabetic     : 2538 bytes   (- 84 bytes)
Case_Ignorable : 1773 bytes   (- 30 bytes)
Cased          : 790 bytes    (- 18 bytes)
Cc             : 26 bytes     (-  6 bytes)
Grapheme_Extend: 1490 bytes   (- 18 bytes)
Lowercase      : 865 bytes    (- 36 bytes)
N              : 1040 bytes   (- 24 bytes)
Uppercase      : 778 bytes    (- 60 bytes)
White_Space    : 85 bytes     (-  6 bytes)
Total table sizes: 9385 bytes (-282 bytes)

src/libcore/unicode/mod.rs

@@ -66,12 +66,12 @@ fn range_search<
     } else {
         let (real_idx, mapping) = bitset_canonicalized[idx - CANONICAL];
         let mut word = bitset_canonical[real_idx as usize];
-        let should_invert = mapping & (1 << 7) != 0;
+        let should_invert = mapping & (1 << 6) != 0;
         if should_invert {
             word = !word;
         }
         // Unset the inversion bit
-        let rotate_by = mapping & !(1 << 7);
+        let rotate_by = mapping & !(1 << 6);
         word = word.rotate_left(rotate_by as u32);
         word
     };

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

@@ -286,13 +286,18 @@ fn range_search<
     } else {
         let (real_idx, mapping) = bitset_canonicalized[idx - CANONICAL];
         let mut word = bitset_canonical[real_idx as usize];
-        let should_invert = mapping & (1 << 7) != 0;
+        let should_invert = mapping & (1 << 6) != 0;
         if should_invert {
             word = !word;
         }
-        // Unset the inversion bit
+        // Lower 6 bits
-        let rotate_by = mapping & !(1 << 7);
+        let quantity = mapping & ((1 << 6) - 1);
-        word = word.rotate_left(rotate_by as u32);
+        if mapping & (1 << 7) != 0 {
+            // shift
+            word >>= quantity as u64;
+        } else {
+            word = word.rotate_left(quantity as u32);
+        }
         word
     };
     (word & (1 << (needle % 64) as u64)) != 0

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

@@ -233,6 +233,7 @@ impl Canonicalized {
             Rotate(u32),
             Invert,
             RotateAndInvert(u32),
+            ShiftRight(u32),
         }
 
         // key is the word being mapped to
@@ -270,6 +271,18 @@ impl Canonicalized {
                         continue 'b;
                     }
                 }
+
+                // All possible shifts
+                for shift_by in 1..64 {
+                    if a == (b >> shift_by) {
+                        mappings
+                            .entry(b)
+                            .or_default()
+                            .push((a, Mapping::ShiftRight(shift_by as u32)));
+                        // We're not interested in further mappings between a and b
+                        continue 'b;
+                    }
+                }
             }
         }
         // These are the bitset words which will be represented "raw" (as a u64)
@@ -384,6 +397,8 @@ impl Canonicalized {
             assert!(distinct_indices.insert(idx));
         }
 
+        const LOWER_6: u32 = (1 << 6) - 1;
+
         let canonicalized_words = canonicalized_words
             .into_iter()
             .map(|v| {
@@ -391,14 +406,18 @@ impl Canonicalized {
                     u8::try_from(v.0).unwrap(),
                     match v.1 {
                         Mapping::RotateAndInvert(amount) => {
-                            assert!(amount < (1 << 7));
+                            assert_eq!(amount, amount & LOWER_6);
-                            1 << 7 | (amount as u8)
+                            1 << 6 | (amount as u8)
                         }
                         Mapping::Rotate(amount) => {
-                            assert!(amount < (1 << 7));
+                            assert_eq!(amount, amount & LOWER_6);
                             amount as u8
                         }
-                        Mapping::Invert => 1 << 7,
+                        Mapping::Invert => 1 << 6,
+                        Mapping::ShiftRight(shift_by) => {
+                            assert_eq!(shift_by, shift_by & LOWER_6);
+                            1 << 7 | (shift_by as u8)
+                        }
                     },
                 )
             })