From 4a5d2b419698fcf7a5e3f68b51e9cdff8f872a26 Mon Sep 17 00:00:00 2001
From: Federico Stra <stra.federico@gmail.com>
Date: Fri, 15 Sep 2023 17:36:54 +0200
Subject: [PATCH] checked_ilog: improve performance

Addresses #115874
---
 library/core/src/num/int_macros.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 1f43520e1b30a..aed6a34788d86 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -2477,18 +2477,18 @@ macro_rules! int_impl {
                 None
             } else {
                 let mut n = 0;
-                let mut r = self;
+                let mut r = 1;
 
                 // Optimization for 128 bit wide integers.
                 if Self::BITS == 128 {
                     let b = Self::ilog2(self) / (Self::ilog2(base) + 1);
                     n += b;
-                    r /= base.pow(b as u32);
+                    r *= base.pow(b);
                 }
 
-                while r >= base {
-                    r /= base;
+                while r <= self / base {
                     n += 1;
+                    r *= base;
                 }
                 Some(n)
             }