From e427ba9cd59dc876d27e4a71104b5156460ca618 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrewrk@noreply.codeberg.org>
Date: Thu, 27 Nov 2025 20:48:54 +0100
Subject: [PATCH] std.sort.partitionPoint: faster implementation (#30005)

Migrated from https://github.com/ziglang/zig/pull/21419

Co-authored-by: Jonathan Hallstrom <lmj.hallstrom@gmail.com>
Reviewed-on: https://codeberg.org/ziglang/zig/pulls/30005
---
 lib/std/sort.zig | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/lib/std/sort.zig b/lib/std/sort.zig
index 8705d24017..9bee64ebe5 100644
--- a/lib/std/sort.zig
+++ b/lib/std/sort.zig
@@ -678,18 +678,23 @@ pub fn partitionPoint(
     context: anytype,
     comptime predicate: fn (@TypeOf(context), T) bool,
 ) usize {
-    var low: usize = 0;
-    var high: usize = items.len;
+    var it: usize = 0;
+    var len: usize = items.len;
 
-    while (low < high) {
-        const mid = low + (high - low) / 2;
-        if (predicate(context, items[mid])) {
-            low = mid + 1;
-        } else {
-            high = mid;
+    while (len > 1) {
+        const half: usize = len / 2;
+        len -= half;
+        if (predicate(context, items[it + half - 1])) {
+            @branchHint(.unpredictable);
+            it += half;
         }
     }
-    return low;
+
+    if (it < items.len) {
+        it += @intFromBool(predicate(context, items[it]));
+    }
+
+    return it;
 }
 
 test partitionPoint {