Provide an optimized implementation of ffs(3) in libc on

aarch64/powerpc/powerpc64, making use of the count leading
zeros instruction.  Also add a brief regression test.
ok deraadt@ kettenis@

6 files changed, 55 insertions, 6 deletions

diff --git a/lib/libc/arch/aarch64/string/Makefile.inc b/lib/libc/arch/aarch64/string/Makefile.inc
index a44e1d0265e..2a65a8da0dd 100644
--- a/lib/libc/arch/aarch64/string/Makefile.inc
+++ b/lib/libc/arch/aarch64/string/Makefile.inc
@@ -1,8 +1,8 @@
-# $OpenBSD: Makefile.inc,v 1.1 2017/01/11 18:09:24 patrick Exp $
+# $OpenBSD: Makefile.inc,v 1.2 2020/06/26 20:16:21 naddy Exp $
 
 SRCS+=	bcopy.c memcpy.c memmove.c \
 	strchr.c strrchr.c \
-	bcmp.c bzero.c ffs.c memchr.c memcmp.c memset.c \
+	bcmp.c bzero.c ffs.S memchr.c memcmp.c memset.c \
 	strcmp.c strncmp.c \
 	strcat.c strcpy.c strcspn.c strlen.c strlcat.c strlcpy.c \
 	strncat.c  strncpy.c strpbrk.c strsep.c \
diff --git a/lib/libc/arch/aarch64/string/ffs.S b/lib/libc/arch/aarch64/string/ffs.S
new file mode 100644
index 00000000000..94995c70110
--- /dev/null
+++ b/lib/libc/arch/aarch64/string/ffs.S
@@ -0,0 +1,18 @@
+/*	$OpenBSD: ffs.S,v 1.1 2020/06/26 20:16:21 naddy Exp $ */
+/*
+ * Written by Christian Weisgerber <naddy@openbsd.org>.
+ * Public domain.
+ */
+ 
+#include "DEFS.h"
+
+ENTRY(ffs)
+	RETGUARD_SETUP(ffs, x15)
+	rbit	w1, w0
+	clz	w1, w1
+	cmp	w0, wzr
+	csinc	w0, wzr, w1, eq
+	RETGUARD_CHECK(ffs, x15)
+	ret
+END(ffs)
+.protected
diff --git a/lib/libc/arch/powerpc/string/Makefile.inc b/lib/libc/arch/powerpc/string/Makefile.inc
index 4a97429a2c3..065455f8679 100644
--- a/lib/libc/arch/powerpc/string/Makefile.inc
+++ b/lib/libc/arch/powerpc/string/Makefile.inc
@@ -1,8 +1,8 @@
-#	$OpenBSD: Makefile.inc,v 1.6 2015/05/15 22:29:37 millert Exp $
+#	$OpenBSD: Makefile.inc,v 1.7 2020/06/26 20:16:21 naddy Exp $
 
 SRCS+=	memcpy.c memmove.S \
 	strchr.c strrchr.c \
-	bcmp.c bzero.c ffs.c memchr.c memcmp.c memset.c strcat.c \
+	bcmp.c bzero.c ffs.S memchr.c memcmp.c memset.c strcat.c \
 	strcmp.c strcpy.c strcspn.c strlen.c strlcat.c strlcpy.c \
 	strncat.c strncmp.c strncpy.c strpbrk.c strsep.c \
 	strspn.c strstr.c swab.c
diff --git a/lib/libc/arch/powerpc/string/ffs.S b/lib/libc/arch/powerpc/string/ffs.S
new file mode 100644
index 00000000000..d7091526d41
--- /dev/null
+++ b/lib/libc/arch/powerpc/string/ffs.S
@@ -0,0 +1,16 @@
+/*	$OpenBSD: ffs.S,v 1.1 2020/06/26 20:16:21 naddy Exp $ */
+/*
+ * Written by Christian Weisgerber <naddy@openbsd.org>.
+ * Public domain.
+ */
+ 
+#include "SYS.h"
+
+ENTRY(ffs)
+	neg	%r4, %r3
+	and	%r3, %r3, %r4
+	cntlzw	%r3, %r3
+	subfic	%r3, %r3, 32
+	blr
+END(ffs)
+.protected
diff --git a/lib/libc/arch/powerpc64/string/Makefile.inc b/lib/libc/arch/powerpc64/string/Makefile.inc
index da0411aa36e..ba6e9dde0e5 100644
--- a/lib/libc/arch/powerpc64/string/Makefile.inc
+++ b/lib/libc/arch/powerpc64/string/Makefile.inc
@@ -1,8 +1,8 @@
-#	$OpenBSD: Makefile.inc,v 1.1 2020/06/25 02:34:22 drahn Exp $
+#	$OpenBSD: Makefile.inc,v 1.2 2020/06/26 20:16:21 naddy Exp $
 
 SRCS+=	memcpy.c memmove.S \
 	strchr.c strrchr.c \
-	bcmp.c bzero.c ffs.c memchr.c memcmp.c memset.c strcat.c \
+	bcmp.c bzero.c ffs.S memchr.c memcmp.c memset.c strcat.c \
 	strcmp.c strcpy.c strcspn.c strlen.c strlcat.c strlcpy.c \
 	strncat.c strncmp.c strncpy.c strpbrk.c strsep.c \
 	strspn.c strstr.c swab.c
diff --git a/lib/libc/arch/powerpc64/string/ffs.S b/lib/libc/arch/powerpc64/string/ffs.S
new file mode 100644
index 00000000000..8e656698ec9
--- /dev/null
+++ b/lib/libc/arch/powerpc64/string/ffs.S
@@ -0,0 +1,15 @@
+/*	$OpenBSD: ffs.S,v 1.1 2020/06/26 20:16:21 naddy Exp $ */
+/*
+ * Written by Christian Weisgerber <naddy@openbsd.org>.
+ * Public domain.
+ */
+ 
+#include "DEFS.h"
+
+ENTRY(ffs)
+	neg	%r4, %r3
+	and	%r3, %r3, %r4
+	cntlzw	%r3, %r3
+	subfic	%r3, %r3, 32
+	blr
+END_BUILTIN(ffs)