From: Wilco Dijkstra <wilco.dijkstra@arm.com>
Date: Tue, 18 Mar 2025 12:14:52 +0000 (+0000)
Subject: malloc: Improve csize2tidx
X-Git-Tag: glibc-2.42~383
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=575de3d6663273b9d4d8fd483a9b45a971aac3af;p=thirdparty%2Fglibc.git

malloc: Improve csize2tidx

Remove the alignment rounding up from csize2tidx - this makes no sense
since the input should be a chunk size.  Removing it enables further
optimizations, for example chunksize_nomask can be safely used and
invalid sizes < MINSIZE are not mapped to a valid tidx.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
---

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 931ca48112..55fb2ab0ec 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -298,7 +298,7 @@
 # define tidx2usize(idx)	(((size_t) idx) * MALLOC_ALIGNMENT + MINSIZE - SIZE_SZ)
 
 /* When "x" is from chunksize().  */
-# define csize2tidx(x) (((x) - MINSIZE + MALLOC_ALIGNMENT - 1) / MALLOC_ALIGNMENT)
+# define csize2tidx(x) (((x) - MINSIZE) / MALLOC_ALIGNMENT)
 /* When "x" is a user-provided size.  */
 # define usize2tidx(x) csize2tidx (request2size (x))