Add an initial set of arm optimized string functions. These

do seem to make noticable speed improvement...
 -Erik

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;
+