Module Name: src
Committed By: matt
Date: Fri Dec 28 05:15:08 UTC 2012
Modified Files:
src/common/lib/libc/arch/arm/string: strlen_neon.S
Log Message:
Debug. This becomes faster than the normal strlen at about 80 characters.
To generate a diff of this commit:
cvs rdiff -u -r1.2 -r1.3 src/common/lib/libc/arch/arm/string/strlen_neon.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/common/lib/libc/arch/arm/string/strlen_neon.S
diff -u src/common/lib/libc/arch/arm/string/strlen_neon.S:1.2 src/common/lib/libc/arch/arm/string/strlen_neon.S:1.3
--- src/common/lib/libc/arch/arm/string/strlen_neon.S:1.2 Sat Dec 15 22:23:31 2012
+++ src/common/lib/libc/arch/arm/string/strlen_neon.S Fri Dec 28 05:15:08 2012
@@ -29,32 +29,31 @@
#include <machine/asm.h>
-RCSID("$NetBSD: strlen_neon.S,v 1.2 2012/12/15 22:23:31 matt Exp $")
+RCSID("$NetBSD: strlen_neon.S,v 1.3 2012/12/28 05:15:08 matt Exp $")
.text
ENTRY(strlen)
- mov ip, r0 /* we r0 for return value */
+ mov ip, r0 /* we use r0 for return value */
ands r1, r0, #15 /* verify qword alignment */
neg r0, r1 /* subtract misalignment from count */
veor q2, q2, q2 /* clear mask */
mov r3, #7 /* NBBY - 1 */
vdup.32 q3, r3 /* dup throughout q3 */
- mov r3, #0x04 /* magic since there are 4 bytes per U32 */
- orr r3, r3, lsl #8 /* copy to next 8 bits */
+ movw r3, #0x0404 /* magic since there are 4 bytes per U32 */
orr r3, r3, lsl #16 /* copy to upper 16 bits */
beq .Lmain_loop
veor q0, q0, q0 /* clear q0 */
vmvn q2, q2 /* set all 16 bytes of mask to all 1s */
bic ip, ip, #15 /* qword align string address */
- lsl r2, r1, #3 /* convert to bits */
- neg r2, r2 /* make negative since we are shifting right */
- tst r1, #8 /* do we need skip the first 8? */
- bne 1f /* yes, we need to skip */
- veor d4, d4, d4 /* clear lower 8 bytes (upper is set) */
- vmov s2, r2 /* set shift amount for upper half */
- b 2f
-1: vmov s0, r2 /* set shift amount for lower half */
-2: vshl.u64 q2, q2, q0 /* shift */
+ lsl r1, r1, #3 /* convert to bits */
+ cmp r1, #64
+ rsbgt r1, r1, #128 /* > 64? BE so we are shifting LSW right */
+ movgt r2, #0 /* > 64? leave MSW alone */
+ rsble r2, r1, #64 /* <=64? BE so we are shifting MSW right */
+ movle r1, #64 /* <=64? clear LSW */
+ vmov d0, r1, r2 /* set shifts for lower and upper halves */
+ vmovl.u32 q0, d0 /* 2 U32 -> 2 U64 */
+ vshl.u64 q2, q2, q0 /* shift */
/*
* Main loop. Load 16 bytes, do a clz,
*/
@@ -65,25 +64,23 @@ ENTRY(strlen)
#endif
vswp d0, d1 /* swap dwords to get BE qword */
vorr q0, q0, q2 /* or "in" leading byte mask */
- veor q2, q2, q2 /* clear byte mask */
+ veor q2, q2, q2 /* clear leading byte mask */
vceq.i8 q1, q0, #0 /* test each byte for 0 */
/* Why couldn't there be a 64-bit CLZ? */
- vclz.i32 q1, q1 /* count leading zeroes to find the 0 byte */
- vadd.i32 q1, q1, q3 /* round up to byte bounary */
+ vclz.u32 q1, q1 /* count leading zeroes to find the 0 byte */
+ vadd.u32 q1, q1, q3 /* round up to byte bounary */
vshr.u32 q1, q1, #3 /* convert to bytes */
- vmovn.i32 d0, q1 /* 4 I32 -> 4 I16 */
- vmovn.i16 d0, q0 /* 4 I16 -> 4 I8 */
+ vmovn.u32 d0, q1 /* 4 I32 -> 4 I16 */
+ vmovn.u16 d0, q0 /* 4 I16 -> 4 I8 */
vmov r2, s0 /* get counts */
- cmp r2, r3 /* count eq 4 in each byte? */
- addeq r0, #16 /* no NULs */
+ eors r2, r2, r3 /* xor with 0x04040404 */
+ addeq r0, #16 /* 0? no NULs */
beq .Lmain_loop /* get next qword */
- /* r2[31:24] already has 1st word byte count */
- tst r2, #(4 << 24) /* first word has 4 non-NUL? */
- addne r2, r2, r2, lsl #8 /* add second word byte-count */
- tstne r2, #(4 << 16) /* second word has 4 non-NUL? */
- addne r2, r2, r2, lsl #16 /* add thirs word byte-count */
- tstne r2, #(4 << 8) /* third has 4 non-NULL? */
- addne r2, r2, r2, lsl #24 /* add fourth word byte-count */
- add r0, r0, r2, lsr #24 /* add accumulated byte-count to length */
+ clz ip, r2 /* count leading zeros */
+ mov r2, r2, lsl ip /* discard them */
+ mov ip, ip, lsr #3 /* divide leading zeroes by 8 */
+ add r0, r0, ip, lsl #2 /* multiple by 4 and add to count */
+ and r2, r2, #(3 << 29)
+ add r0, r0, r2, lsr #29
RET /* and return. */
END(strlen)
