From 05ff71f187aa06e51f1eceb1c85cf439d09c790a Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@mit.edu>
Date: Fri, 2 Mar 2018 20:29:37 -0500
Subject: [PATCH] performance tweak in reverse(::String) (#26300)

No reason not to pass a `sizehint` in this function since we know the exact number of bytes required.
---
 base/strings/substring.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/base/strings/substring.jl b/base/strings/substring.jl
index 879955daeba48..631d191dd678b 100644
--- a/base/strings/substring.jl
+++ b/base/strings/substring.jl
@@ -130,7 +130,7 @@ julia> join(reverse(collect(graphemes("ax̂e")))) # reverses graphemes
 ```
 """
 function reverse(s::Union{String,SubString{String}})::String
-    sprint() do io
+    sprint(sizehint=sizeof(s)) do io
         i, j = firstindex(s), lastindex(s)
         while i ≤ j
             c, j = s[j], prevind(s, j)