On 7/3/23 1:23 PM, Robert Clausecker wrote:
The branch main has been updated by fuz:
URL:
https://cgit.FreeBSD.org/src/commit/?id=ee8b0c436d7221c25e8be3c3fe1f9da78b9d5b16
commit ee8b0c436d7221c25e8be3c3fe1f9da78b9d5b16
Author: Robert Clausecker <[email protected]>
AuthorDate: 2023-06-23 16:22:54 +0000
Commit: Robert Clausecker <[email protected]>
CommitDate: 2023-07-03 20:18:27 +0000
lib/libc/string: replace ffs/fls implementations with clang builtins
Most architectures we support (except for riscv64) have instructions
to compute these functions very quickly. Replace old code with the
ffs and clz builtin functions, allowing clang to generate good code
for all architectures.
As a consequence, toss out arm and i386 ffs() implementations.
Sponsored by: FreeBSD Foundation
Approved by: mhorne
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D40730
---
lib/libc/arm/string/Makefile.inc | 1 -
lib/libc/arm/string/ffs.S | 57 ---------------------------------------
lib/libc/i386/string/Makefile.inc | 1 -
lib/libc/i386/string/ffs.S | 56 --------------------------------------
lib/libc/string/ffs.c | 12 ++++-----
lib/libc/string/ffsl.c | 12 ++++-----
lib/libc/string/ffsll.c | 12 ++++-----
lib/libc/string/fls.c | 13 +++++----
lib/libc/string/flsl.c | 14 +++++-----
lib/libc/string/flsll.c | 13 +++++----
10 files changed, 34 insertions(+), 157 deletions(-)
diff --git a/lib/libc/string/ffs.c b/lib/libc/string/ffs.c
index 738ef90ce091..c011b3390612 100644
--- a/lib/libc/string/ffs.c
+++ b/lib/libc/string/ffs.c
@@ -3,6 +3,10 @@
*
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
+ * Copyright (c) 2023 The FreeBSD Foundation
+ *
+ * Portions of this software were developed by Robert Clausecker
+ * <[email protected]> under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@@ -43,11 +47,5 @@ __FBSDID("$FreeBSD$");
int
ffs(int mask)
{
- int bit;
-
- if (mask == 0)
- return(0);
- for (bit = 1; !(mask & 1); bit++)
- mask = (unsigned int)mask >> 1;
- return (bit);
+ return (__builtin_ffs(mask));
This breaks the build on GCC:
/usr/home/john/work/freebsd/main/lib/libc/string/ffs.c: In function 'ffs':
/usr/home/john/work/freebsd/main/lib/libc/string/ffs.c:48:1: error: infinite
recursion detected [-Werror=infinite-recursion]
48 | ffs(int mask)
| ^~~
/usr/home/john/work/freebsd/main/lib/libc/string/ffs.c:50:17: note: recursive
call
50 | return (__builtin_ffs(mask));
| ~^~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
*** Error code 1
--
John Baldwin
