From a1c70a667c05438bb4855c02fe72bfe18391bed0 Mon Sep 17 00:00:00 2001
From: otto <>
Date: Thu, 18 Jan 2018 08:37:28 +0000
Subject: [PATCH] Move to ffs(3) for bitmask scanning. I played with this
 earlier, but at that time ffs function calls were generated instead of the
 compiler inlining the code.  Now that ffs is marked protected in libc this is
 handled better.  Thanks to kshe who prompted me to look at this again.

---
 src/lib/libc/stdlib/malloc.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/src/lib/libc/stdlib/malloc.c b/src/lib/libc/stdlib/malloc.c
index b0083cb9..40c602a1 100644
--- a/src/lib/libc/stdlib/malloc.c
+++ b/src/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.239 2018/01/08 12:20:23 otto Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.240 2018/01/18 08:37:28 otto Exp $	*/
 /*
  * Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -931,7 +931,7 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
 	u_int i, r;
 	int j, listnum;
 	size_t k;
-	u_short	u, b, *lp;
+	u_short	*lp;
 	struct chunk_info *bp;
 	void *p;
 
@@ -960,15 +960,12 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
 	/* start somewhere in a short */
 	lp = &bp->bits[i / MALLOC_BITS];
 	if (*lp) {
-		b = *lp;
-		k = i % MALLOC_BITS;
-		u = 1 << k;
-		while (k < MALLOC_BITS) {
-			if (b & u)
-				goto found;
-			k++;
-			u <<= 1;
-		} 
+		j = i % MALLOC_BITS;
+		k = ffs(*lp >> j);
+		if (k != 0) {
+			k += j - 1;
+			goto found;
+		}
 	}
 	/* no bit halfway, go to next full short */
 	i /= MALLOC_BITS;
@@ -977,15 +974,8 @@ malloc_bytes(struct dir_info *d, size_t size, void *f)
 			i = 0;
 		lp = &bp->bits[i];
 		if (*lp) {
-			b = *lp;
-			k = 0;
-			u = 1;
-			for (;;) {
-				if (b & u)
-					goto found;
-				k++;
-				u <<= 1;
-			}
+			k = ffs(*lp) - 1;
+			break;
 		}
 	}
 found:
@@ -996,7 +986,7 @@ found:
 	}
 #endif
 
-	*lp ^= u;
+	*lp ^= 1 << k;
 
 	/* If there are no more free, remove from free-list */
 	if (--bp->free == 0)