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authorRichard Henderson <rth@twiddle.net>2014-02-12 06:54:57 -0800
committerRichard Henderson <rth@twiddle.net>2014-02-12 07:00:06 -0800
commit68b7efaadb1b6045a56277ea62d324c20ac0b633 (patch)
tree07b51c9866373430373fb90b252d46c23cc1707e /sysdeps/alpha/strlen.S
parent8fd7b0d5591e59ed5cb3078b351bd49314a66cef (diff)
Relocate alpha from ports to libc
Also fixed the following whitespace nits to satisfy the push: sysdeps/alpha/alphaev6/memset.S:142: space before tab in indent. sysdeps/alpha/configure:1: new blank line at EOF. sysdeps/alpha/fpu/e_sqrt.c:126: space before tab in indent. sysdeps/alpha/preconfigure:1: new blank line at EOF. sysdeps/unix/sysv/linux/alpha/syscalls.list:1: new blank line at EOF.
Diffstat (limited to 'sysdeps/alpha/strlen.S')
-rw-r--r--sysdeps/alpha/strlen.S76
1 files changed, 76 insertions, 0 deletions
diff --git a/sysdeps/alpha/strlen.S b/sysdeps/alpha/strlen.S
new file mode 100644
index 0000000000..3e55220fad
--- /dev/null
+++ b/sysdeps/alpha/strlen.S
@@ -0,0 +1,76 @@
+/* Copyright (C) 1996-2014 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)