arm: Add optimized ffs for armv6t2

3 files changed, 88 insertions, 0 deletions

diff --git a/ports/ChangeLog.arm b/ports/ChangeLog.arm
index 288dfb4c09..55e63fa368 100644
--- a/ports/ChangeLog.arm
+++ b/ports/ChangeLog.arm
@@ -1,5 +1,8 @@
 2013-03-06  Richard Henderson <rth@redhat.com>
 
+	* sysdeps/arm/armv6t2/ffs.S: New file.
+	* sysdeps/arm/armv6t2/ffsll.S: New file.
+
 	* sysdeps/arm/sysdep.h (ARCH_HAS_HARD_TP): New macro.
 	(GET_TLS): Use hard-tp if ARCH_HAS_HARD_TP.
 	* sysdeps/unix/sysv/linux/arm/aeabi_read_tp.S: Likewise.
diff --git a/ports/sysdeps/arm/armv6t2/ffs.S b/ports/sysdeps/arm/armv6t2/ffs.S
new file mode 100644
index 0000000000..b2c88b9460
--- /dev/null
+++ b/ports/sysdeps/arm/armv6t2/ffs.S
@@ -0,0 +1,35 @@
+/* ffs -- find first set bit in an int, from least significant end.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+	.syntax unified
+	.text
+
+ENTRY (__ffs)
+	cmp	r0, #0
+	rbit	r0, r0
+	itt	ne
+	clzne	r0, r0
+	addne	r0, r0, #1
+	bx	lr
+END (__ffs)
+
+weak_alias (__ffs, ffs)
+weak_alias (__ffs, ffsl)
+libc_hidden_builtin_def (ffs)
diff --git a/ports/sysdeps/arm/armv6t2/ffsll.S b/ports/sysdeps/arm/armv6t2/ffsll.S
new file mode 100644
index 0000000000..e49c70fdf1
--- /dev/null
+++ b/ports/sysdeps/arm/armv6t2/ffsll.S
@@ -0,0 +1,50 @@
+/* ffsll -- find first set bit in a long long, from least significant end.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+	.syntax unified
+	.text
+
+ENTRY (ffsll)
+	@ If low part is 0, operate on the high part.  Ensure that the
+	@ word on which we operate is in r0.  Set r2 to the bit offset
+	@ of the word being considered.  Set the flags for the word
+	@ being operated on.
+#ifdef __ARMEL__
+	cmp	r0, #0
+	itee	ne
+	movne	r2, #0
+	moveq	r2, #32
+	movseq	r0, r1
+#else
+	cmp	r1, #0
+	ittee	ne
+	movne	r2, #0
+	movne	r0, r1
+	moveq	r2, #32
+	cmpeq	r0, #0
+#endif
+	@ Perform the ffs on r0.
+	rbit	r0, r0
+	ittt	ne
+	clzne	r0, r0
+	addne	r2, r2, #1
+	addne	r0, r0, r2
+	bx	lr
+END (ffsll)