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Diffstat (limited to 'ports/sysdeps/arm/armv6/strcpy.S')
| -rw-r--r-- | ports/sysdeps/arm/armv6/strcpy.S | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/ports/sysdeps/arm/armv6/strcpy.S b/ports/sysdeps/arm/armv6/strcpy.S new file mode 100644 index 0000000000..41f6443319 --- /dev/null +++ b/ports/sysdeps/arm/armv6/strcpy.S @@ -0,0 +1,218 @@ +/* strcpy -- copy a nul-terminated string. + Copyright (C) 2013 Free Software Foundation, Inc. + 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/>. */ + +#include <sysdep.h> + +/* Endian independent macros for shifting bytes within registers. */ +#ifdef __ARMEB__ +#define lsh_gt lsr +#define lsh_ls lsl +#else +#define lsh_gt lsl +#define lsh_ls lsr +#endif + + .syntax unified + .text + +ENTRY (__stpcpy) + @ Signal stpcpy with NULL in IP. + mov ip, #0 + b 0f +END (__stpcpy) + +weak_alias (__stpcpy, stpcpy) +libc_hidden_def (__stpcpy) +libc_hidden_builtin_def (stpcpy) + +ENTRY (strcpy) + @ Signal strcpy with DEST in IP. + mov ip, r0 +0: + pld [r0] + pld [r1] + + @ To cater to long strings, we want 8 byte alignment in the source. + @ To cater to small strings, we don't want to start that right away. + @ Loop up to 16 times, less whatever it takes to reach alignment. + and r3, r1, #7 + rsb r3, r3, #16 + + @ Loop until we find ... +1: ldrb r2, [r1], #1 + subs r3, r3, #1 @ ... the alignment point + strb r2, [r0], #1 + it ne + cmpne r2, #0 @ ... or EOS + bne 1b + + @ Disambiguate the exit possibilites above + cmp r2, #0 @ Found EOS + beq .Lreturn + + @ Load the next two words asap + ldrd r2, r3, [r1], #8 + pld [r0, #64] + pld [r1, #64] + + @ For longer strings, we actaully need a stack frame. + push { r4, r5, r6, r7 } + cfi_adjust_cfa_offset (16) + cfi_rel_offset (r4, 0) + cfi_rel_offset (r5, 4) + cfi_rel_offset (r6, 8) + cfi_rel_offset (r7, 12) + + @ Subtracting (unsigned saturating) from 1 for any byte means result + @ of 1 for any byte that was originally zero and 0 otherwise. + @ Therefore we consider the lsb of each byte the "found" bit. +#ifdef ARCH_HAS_T2 + movw r7, #0x0101 + tst r0, #3 @ Test alignment of DEST + movt r7, #0x0101 +#else + ldr ip, =0x01010101 + tst r0, #3 +#endif + bne .Lunaligned + + @ So now source (r1) is aligned to 8, and dest (r0) is aligned to 4. + @ Loop, reading 8 bytes at a time, searching for EOS. + .balign 16 +2: uqsub8 r4, r7, r2 @ Find EOS + uqsub8 r5, r7, r3 + pld [r1, #128] + cmp r4, #0 @ EOS in first word? + pld [r0, #128] + bne 3f + str r2, [r0], #4 + cmp r5, #0 @ EOS in second word? + bne 4f + str r3, [r0], #4 + ldrd r2, r3, [r1], #8 + b 2b + +3: sub r1, r1, #4 @ backup to first word +4: sub r1, r1, #4 @ backup to second word + + @ ... then finish up any tail a byte at a time. + @ Note that we generally back up and re-read source bytes, + @ but we'll not re-write dest bytes. +.Lbyte_loop: + ldrb r2, [r1], #1 + cmp r2, #0 + strb r2, [r0], #1 + bne .Lbyte_loop + + pop { r4, r5, r6, r7 } + cfi_remember_state + cfi_adjust_cfa_offset (-16) + cfi_restore (r4) + cfi_restore (r5) + cfi_restore (r6) + cfi_restore (r7) + +.Lreturn: + cmp ip, #0 @ Was this strcpy or stpcpy? + ite eq + subeq r0, r0, #1 @ stpcpy: undo post-inc from store + movne r0, ip @ strcpy: return original dest + bx lr + +.Lunaligned: + cfi_restore_state + @ Here, source is aligned to 8, but the destination is not word + @ aligned. Therefore we have to shift the data in order to be + @ able to perform aligned word stores. + + @ Find out which misalignment we're dealing with. + tst r0, #1 + beq .Lunaligned2 + tst r0, #2 + bne .Lunaligned3 + @ Fallthru to .Lunaligned1. + +.macro unaligned_copy unalign + @ Prologue to unaligned loop. Seed shifted non-zero bytes. + uqsub8 r4, r7, r2 @ Find EOS + uqsub8 r5, r7, r3 + mvns r4, r4 @ EOS in first word? + it ne + subne r1, r1, #8 + bne .Lbyte_loop +#ifdef __ARMEB__ + rev r2, r2 @ Byte stores below need LE data +#endif + @ Store a few bytes from the first word. + @ At the same time we align r0 and shift out bytes from r2. +.rept 4-\unalign + strb r2, [r0], #1 + lsr r2, r2, #8 +.endr +#ifdef __ARMEB__ + rev r2, r2 @ Undo previous rev +#endif + @ Rotated unaligned copy loop. The tail of the prologue is + @ shared with the loop itself. + .balign 8 +1: mvns r5, r5 @ EOS in second word? + bne 4f + @ Combine first and second words + orr r2, r2, r3, lsh_gt #(\unalign*8) + @ Save leftover bytes from the two words + lsh_ls r6, r3, #((4-\unalign)*8) + str r2, [r0], #4 + @ The "real" start of the unaligned copy loop. + ldrd r2, r3, [r1], #8 @ Load 8 more bytes + uqsub8 r4, r7, r2 @ Find EOS + pld [r1, #128] + uqsub8 r5, r7, r3 + pld [r0, #128] + mvns r4, r4 @ EOS in first word? + bne 3f + @ Combine the leftover and the first word + orr r6, r6, r2, lsh_gt #(\unalign*8) + @ Discard used bytes from the first word. + lsh_ls r2, r2, #((4-\unalign)*8) + str r6, [r0], #4 + b 1b + @ Found EOS in one of the words; adjust backward +3: sub r1, r1, #4 + mov r2, r6 +4: sub r1, r1, #4 + @ And store the remaining bytes from the leftover +#ifdef __ARMEB__ + rev r2, r2 +#endif +.rept \unalign + strb r2, [r0], #1 + lsr r2, r2, #8 +.endr + b .Lbyte_loop +.endm + +.Lunaligned1: + unaligned_copy 1 +.Lunaligned2: + unaligned_copy 2 +.Lunaligned3: + unaligned_copy 3 + +END (strcpy) + +libc_hidden_builtin_def (strcpy) |