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Diffstat (limited to 'newlib/libc/machine/arm/strlen-armv7.S')
| -rw-r--r-- | newlib/libc/machine/arm/strlen-armv7.S | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/newlib/libc/machine/arm/strlen-armv7.S b/newlib/libc/machine/arm/strlen-armv7.S new file mode 100644 index 000000000..d6e2831ff --- /dev/null +++ b/newlib/libc/machine/arm/strlen-armv7.S @@ -0,0 +1,127 @@ +/* Copyright (c) 2010-2011, Linaro Limited + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + + * Neither the name of Linaro Limited nor the names of its + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + + Written by Dave Gilbert <david.gilbert@linaro.org> + + This strlen routine is optimised on a Cortex-A9 and should work on + all ARMv7 processors. This routine is reasonably fast for short + strings, but is probably slower than a simple implementation if all + your strings are very short */ + +@ 2011-02-08 david.gilbert@linaro.org +@ Extracted from local git 6848613a +@ 2011-10-13 david.gilbert@linaro.org +@ Extracted from cortex-strings bzr rev 63 +@ Integrate to newlib, flip to ldrd +@ Pull in Endian macro from my memchr + +#include "arm_asm.h" + +@ NOTE: This ifdef MUST match the ones in arm/strlen.c +@ We fallback to the one in arm/strlen.c for size optimised or +@ for older arch's +#if defined(_ISA_ARM_7) || defined(__ARM_ARCH_6T2__) && \ + !(defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \ + (defined (__thumb__) && !defined (__thumb2__))) + +@ this lets us check a flag in a 00/ff byte easily in either endianness +#ifdef __ARMEB__ +#define CHARTSTMASK(c) 1<<(31-(c*8)) +#else +#define CHARTSTMASK(c) 1<<(c*8) +#endif + +@------------------------------------------------------------------------------ + .syntax unified + .arch armv7-a + + .thumb_func + .align 2 + .p2align 4,,15 + .global strlen + .type strlen,%function +strlen: + @ r0 = string + @ returns count of bytes in string not including terminator + mov r1, r0 + push { r4,r6 } + mvns r6, #0 @ all F + movs r4, #0 + tst r0, #7 + beq 2f + +1: + ldrb r2, [r1], #1 + tst r1, #7 @ Hit alignment yet? + cbz r2, 10f @ Exit if we found the 0 + bne 1b + + @ So we're now aligned +2: + ldrd r2,r3,[r1],#8 + uadd8 r2, r2, r6 @ Par add 0xff - sets the GE bits for bytes!=0 + sel r2, r4, r6 @ bytes are 00 for none-00 bytes, + @ or ff for 00 bytes - NOTE INVERSION + uadd8 r3, r3, r6 @ Par add 0xff - sets the GE bits for bytes!=0 + sel r3, r2, r6 @ chained...bytes are 00 for none-00 bytes, + @ or ff for 00 bytes - NOTE INVERSION + cmp r3, #0 + beq 2b + +strlenendtmp: + @ One (or more) of the bytes we loaded was 0 - but which one? + @ r2 has the mask corresponding to the first loaded word + @ r3 has a combined mask of the two words - but if r2 was all-non 0 + @ then it's just the 2nd words + cmp r2, #0 + itte eq + moveq r2, r3 @ the end is in the 2nd word + subeq r1,r1,#3 + subne r1,r1,#7 + + @ r1 currently points to the 2nd byte of the word containing the 0 + tst r2, # CHARTSTMASK(0) @ 1st character + bne 10f + adds r1,r1,#1 + tst r2, # CHARTSTMASK(1) @ 2nd character + ittt eq + addeq r1,r1,#1 + tsteq r2, # (3<<15) @ 2nd & 3rd character + @ If not the 3rd must be the last one + addeq r1,r1,#1 + +10: + @ r0 is still at the beginning, r1 is pointing 1 byte after the nul + sub r0, r1, r0 + subs r0, r0, #1 + pop { r4, r6 } + bx lr + +#endif |