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authorEric Andersen <andersen@codepoet.org>2003-11-20 15:23:03 +0000
committerEric Andersen <andersen@codepoet.org>2003-11-20 15:23:03 +0000
commitee4435bcd6f94b7463cbd7e960e84ddf03965272 (patch)
tree4d8ab5b8d85897e3b0844ad26b804300e90a2d81 /libc/string/arm/strlen.S
parent72a8f4125ba443d28f9398a45ec5c4c9504c3e8f (diff)
Add an initial set of arm optimized string functions. These
do seem to make noticable speed improvement... -Erik
Diffstat (limited to 'libc/string/arm/strlen.S')
-rw-r--r--libc/string/arm/strlen.S71
1 files changed, 71 insertions, 0 deletions
diff --git a/libc/string/arm/strlen.S b/libc/string/arm/strlen.S
new file mode 100644
index 000000000..a84114c31
--- /dev/null
+++ b/libc/string/arm/strlen.S
@@ -0,0 +1,71 @@
+/* Copyright (C) 1998 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Code contributed by Matthew Wilcox <willy@odie.barnet.ac.uk>
+
+ 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <endian.h>
+#include <sys/syscall.h>
+
+/* size_t strlen(const char *S)
+ * entry: r0 -> string
+ * exit: r0 = len
+ */
+
+ .text
+ .global strlen;
+ .type strlen,%function
+ .align 4; \
+
+strlen:
+ bic r1, r0, $3 @ addr of word containing first byte
+ ldr r2, [r1], $4 @ get the first word
+ ands r3, r0, $3 @ how many bytes are duff?
+ rsb r0, r3, $0 @ get - that number into counter.
+ beq Laligned @ skip into main check routine if no
+ @ more
+#if __BYTE_ORDER == __BIG_ENDIAN
+ orr r2, r2, $0xff000000 @ set this byte to non-zero
+ subs r3, r3, $1 @ any more to do?
+ orrgt r2, r2, $0x00ff0000 @ if so, set this byte
+ subs r3, r3, $1 @ more?
+ orrgt r2, r2, $0x0000ff00 @ then set.
+#else
+ orr r2, r2, $0x000000ff @ set this byte to non-zero
+ subs r3, r3, $1 @ any more to do?
+ orrgt r2, r2, $0x0000ff00 @ if so, set this byte
+ subs r3, r3, $1 @ more?
+ orrgt r2, r2, $0x00ff0000 @ then set.
+#endif
+Laligned: @ here, we have a word in r2. Does it
+ tst r2, $0x000000ff @ contain any zeroes?
+ tstne r2, $0x0000ff00 @
+ tstne r2, $0x00ff0000 @
+ tstne r2, $0xff000000 @
+ addne r0, r0, $4 @ if not, the string is 4 bytes longer
+ ldrne r2, [r1], $4 @ and we continue to the next word
+ bne Laligned @
+Llastword: @ drop through to here once we find a
+ tst r2, $0x000000ff @ word that has a zero byte in it
+ addne r0, r0, $1 @
+ tstne r2, $0x0000ff00 @ and add up to 3 bytes on to it
+ addne r0, r0, $1 @
+ tstne r2, $0x00ff0000 @ (if first three all non-zero, 4th
+ addne r0, r0, $1 @ must be zero)
+ mov pc,lr
+
+.size strlen,.-strlen;
+