From 1347df898eeb7a0711b5466c5f5c299f463f45e9 Mon Sep 17 00:00:00 2001
From: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Fri, 22 Nov 2024 16:48:44 -0600
Subject: [PATCH] Add ascii fast path for `fish_wcswidth(&wstrw)`

chars.all(|c| c.is_ascii()) is autovectorizable but this outperforms even when
it's not vectorized.
---
 src/fallback.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/fallback.rs b/src/fallback.rs
index 95cdea0be..3e1334479 100644
--- a/src/fallback.rs
+++ b/src/fallback.rs
@@ -89,6 +89,11 @@ pub fn fish_wcwidth(c: char) -> isize {
 /// fish's internal versions of wcwidth and wcswidth, which can use an internal implementation if
 /// the system one is busted.
 pub fn fish_wcswidth(s: &wstr) -> isize {
+    // ascii fast path; empty iterator returns true for .all()
+    if s.chars().all(|c| c.is_ascii() && !c.is_ascii_control()) {
+        return s.len() as isize;
+    }
+
     let mut result = 0;
     for c in s.chars() {
         let w = fish_wcwidth(c);