1 files changed, 76 insertions, 0 deletions
diff --git a/ports/sysdeps/alpha/strlen.S b/ports/sysdeps/alpha/strlen.S
new file mode 100644
index 0000000000..98308efcd7
--- /dev/null
+++ b/ports/sysdeps/alpha/strlen.S
@@ -0,0 +1,76 @@
+/* Copyright (C) 1996, 1997, 2003 Free Software Foundation, Inc.
+   Contributed by David Mosberger (davidm@cs.arizona.edu).
+   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/>.  */
+
+/* Finds length of a 0-terminated string.  Optimized for the Alpha
+   architecture:
+
+      - memory accessed as aligned quadwords only
+      - uses cmpbge to compare 8 bytes in parallel
+      - does binary search to find 0 byte in last quadword (HAKMEM
+	needed 12 instructions to do this instead of the 8 instructions
+	that the binary search needs).
+*/
+
+#include <sysdep.h>
+
+	.set noreorder
+	.set noat
+
+ENTRY(strlen)
+#ifdef PROF
+	ldgp	gp, 0(pv)
+	lda	AT, _mcount
+	jsr	AT, (AT), _mcount
+	.prologue 1
+#else
+	.prologue 0
+#endif
+
+	ldq_u   t0, 0(a0)	# load first quadword (a0 may be misaligned)
+	lda     t1, -1(zero)
+	insqh   t1, a0, t1
+	andnot  a0, 7, v0
+	or      t1, t0, t0
+	nop			# dual issue the next two on ev5
+	cmpbge  zero, t0, t1	# t1 <- bitmask: bit i == 1 <==> i-th byte == 0
+	bne     t1, $found
+
+$loop:	ldq     t0, 8(v0)
+	addq    v0, 8, v0	# addr += 8
+	cmpbge  zero, t0, t1
+	beq     t1, $loop
+
+$found:	negq    t1, t2		# clear all but least set bit
+	and     t1, t2, t1
+
+	and     t1, 0xf0, t2	# binary search for that set bit
+	and	t1, 0xcc, t3
+	and	t1, 0xaa, t4
+	cmovne	t2, 4, t2
+	cmovne	t3, 2, t3
+	cmovne	t4, 1, t4
+	addq	t2, t3, t2
+	addq	v0, t4, v0
+	addq	v0, t2, v0
+	nop			# dual issue next two on ev4 and ev5
+
+	subq    v0, a0, v0
+	ret
+
+	END(strlen)
+libc_hidden_builtin_def (strlen)