Align EMOJI_PRESENTATION_LEAVES to 128 bytes

Ensure rows don't cross cache lines, makes a small difference in the benchmarks
unicode-rs · Apr 22, 2024 · 9bb0575 · 9bb0575
1 parent 2509257
commit 9bb0575
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Showing 3 changed files with 13 additions and 7 deletions.
diff --git a/scripts/unicode.py b/scripts/unicode.py
@@ -561,7 +561,7 @@ def emit_module(
         // Extract the 3-9th (0-indexed) least significant bits of `cp`,
         // and use them to index into `leaf_row`.
         let idx_within_leaf = usize::try_from((cp >> 3) & 0x7F).unwrap();
-        let leaf_byte = EMOJI_PRESENTATION_LEAVES[idx_of_leaf][idx_within_leaf];
+        let leaf_byte = EMOJI_PRESENTATION_LEAVES.0[idx_of_leaf][idx_within_leaf];
 
         // Use the 3 LSB of `cp` to index into `leaf_byte`.
         ((leaf_byte >> (cp & 7)) & 1) == 1
@@ -622,9 +622,12 @@ def emit_module(
 
         module.write(
             f"""
+    #[repr(align(128))]
+    struct Align128<T>(T);
+
     /// Array of 1024-bit bitmaps. Index into the correct (obtained from `EMOJI_PRESENTATION_INDEX`)
     /// bitmap with the 10 LSB of your codepoint to get whether it can start an emoji presentation seq.
-    static EMOJI_PRESENTATION_LEAVES: [[u8; 128]; {len(variation_leaves)}] = [
+    static EMOJI_PRESENTATION_LEAVES: Align128<[[u8; 128]; {len(variation_leaves)}]> = Align128([
 """
         )
         for leaf in variation_leaves:
@@ -636,7 +639,7 @@ def emit_module(
                 module.write("\n")
             module.write("        ],\n")
 
-        module.write("    ];\n")
+        module.write("    ]);\n")
         module.write("}\n")
 
 

diff --git a/src/tables.rs b/src/tables.rs
@@ -81,7 +81,7 @@ pub mod charwidth {
         // Extract the 3-9th (0-indexed) least significant bits of `cp`,
         // and use them to index into `leaf_row`.
         let idx_within_leaf = usize::try_from((cp >> 3) & 0x7F).unwrap();
-        let leaf_byte = EMOJI_PRESENTATION_LEAVES[idx_of_leaf][idx_within_leaf];
+        let leaf_byte = EMOJI_PRESENTATION_LEAVES.0[idx_of_leaf][idx_within_leaf];
 
         // Use the 3 LSB of `cp` to index into `leaf_byte`.
         ((leaf_byte >> (cp & 7)) & 1) == 1
@@ -566,9 +566,12 @@ pub mod charwidth {
         0xFF, 0xFF, 0x5F,
     ];
 
+    #[repr(align(128))]
+    struct Align128<T>(T);
+
     /// Array of 1024-bit bitmaps. Index into the correct (obtained from `EMOJI_PRESENTATION_INDEX`)
     /// bitmap with the 10 LSB of your codepoint to get whether it can start an emoji presentation seq.
-    static EMOJI_PRESENTATION_LEAVES: [[u8; 128]; 6] = [
+    static EMOJI_PRESENTATION_LEAVES: Align128<[[u8; 128]; 6]> = Align128([
         [
             0x00, 0x00, 0x00, 0x00, 0x08, 0x04, 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x42, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -641,5 +644,5 @@ pub mod charwidth {
             0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0x0F,
             0x01, 0x00,
         ],
-    ];
+    ]);
 }
diff --git a/src/tests.rs b/src/tests.rs
@@ -12,7 +12,7 @@
 use std::{iter, string::String};
 
 #[cfg(feature = "bench")]
-use test::{self, Bencher};
+use test::Bencher;
 
 use super::{UnicodeWidthChar, UnicodeWidthStr};