-/* Copyright (c) 2010-2011, Linaro Limited
+/* Copyright (c) 2010-2011,2013 Linaro Limited
All rights reserved.
Redistribution and use in source and binary forms, with or without
(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
+ Assumes:
+ ARMv6T2, AArch32
+ */
#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
+/* 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 architectures. */
#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
+ .macro def_fn f p2align=0
+ .text
+ .p2align \p2align
+ .global \f
+ .type \f, %function
+\f:
+ .endm
+
#ifdef __ARMEB__
-#define CHARTSTMASK(c) 1<<(31-(c*8))
+#define S2LO lsl
+#define S2HI lsr
#else
-#define CHARTSTMASK(c) 1<<(c*8)
+#define S2LO lsr
+#define S2HI lsl
#endif
-@------------------------------------------------------------------------------
+ /* This code requires Thumb. */
+ .thumb
.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 }
+
+/* Parameters and result. */
+#define srcin r0
+#define result r0
+
+/* Internal variables. */
+#define src r1
+#define data1a r2
+#define data1b r3
+#define const_m1 r12
+#define const_0 r4
+#define tmp1 r4 /* Overlaps const_0 */
+#define tmp2 r5
+
+def_fn strlen p2align=6
+ pld [srcin, #0]
+ strd r4, r5, [sp, #-8]!
+ bic src, srcin, #7
+ mvn const_m1, #0
+ ands tmp1, srcin, #7 /* (8 - bytes) to alignment. */
+ pld [src, #32]
+ bne.w .Lmisaligned8
+ mov const_0, #0
+ mov result, #-8
+.Lloop_aligned:
+ /* Bytes 0-7. */
+ ldrd data1a, data1b, [src]
+ pld [src, #64]
+ add result, result, #8
+.Lstart_realigned:
+ uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
+ sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
+ uadd8 data1b, data1b, const_m1
+ sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
+ cbnz data1b, .Lnull_found
+
+ /* Bytes 8-15. */
+ ldrd data1a, data1b, [src, #8]
+ uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
+ add result, result, #8
+ sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
+ uadd8 data1b, data1b, const_m1
+ sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
+ cbnz data1b, .Lnull_found
+
+ /* Bytes 16-23. */
+ ldrd data1a, data1b, [src, #16]
+ uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
+ add result, result, #8
+ sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
+ uadd8 data1b, data1b, const_m1
+ sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
+ cbnz data1b, .Lnull_found
+
+ /* Bytes 24-31. */
+ ldrd data1a, data1b, [src, #24]
+ add src, src, #32
+ uadd8 data1a, data1a, const_m1 /* Saturating GE<0:3> set. */
+ add result, result, #8
+ sel data1a, const_0, const_m1 /* Select based on GE<0:3>. */
+ uadd8 data1b, data1b, const_m1
+ sel data1b, data1a, const_m1 /* Only used if d1a == 0. */
+ cmp data1b, #0
+ beq .Lloop_aligned
+
+.Lnull_found:
+ cmp data1a, #0
+ itt eq
+ addeq result, result, #4
+ moveq data1a, data1b
+#ifndef __ARMEB__
+ rev data1a, data1a
+#endif
+ clz data1a, data1a
+ ldrd r4, r5, [sp], #8
+ add result, result, data1a, lsr #3 /* Bits -> Bytes. */
bx lr
+.Lmisaligned8:
+ ldrd data1a, data1b, [src]
+ and tmp2, tmp1, #3
+ rsb result, tmp1, #0
+ lsl tmp2, tmp2, #3 /* Bytes -> bits. */
+ tst tmp1, #4
+ pld [src, #64]
+ S2HI tmp2, const_m1, tmp2
+ orn data1a, data1a, tmp2
+ itt ne
+ ornne data1b, data1b, tmp2
+ movne data1a, const_m1
+ mov const_0, #0
+ b .Lstart_realigned
+ .size strlen, . - strlen
+
#endif
git://sourceware.org / newlib-cygwin.git / commitdiff