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2013-01-17 Marcus Shawcroft <marcus.shawcroft@linaro.org> 

* libc/machine/aarch64/strnlen.S: Correct arithmetic for
	argument N values close to the maximum representable
	value in an unsigned 64 bit value.
This commit is contained in:
Marcus Shawcroft 2013-01-17 14:52:37 +00:00
parent 211dd84b83
commit 78f66de6ce
2 changed files with 34 additions and 11 deletions
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6
newlib/ChangeLog
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@ -1,3 +1,9 @@
2013-01-17 Marcus Shawcroft <marcus.shawcroft@linaro.org>
* libc/machine/aarch64/strnlen.S: Correct arithmetic for
argument N values close to the maximum representable
value in an unsigned 64 bit value.
2013-01-15 Nick Clifton <nickc@redhat.com>
* libc/sys/sysnecv850/crt0.S (_start): Enable FPU for the

39
newlib/libc/machine/aarch64/strnlen.S
View File

@ -85,8 +85,10 @@ def_fn strnlen
bic src, srcin, #15
ands tmp1, srcin, #15
b.ne .Lmisaligned
add limit_wd, limit, #15
lsr limit_wd, limit_wd, #4
/* Calculate the number of full and partial words -1. */
sub limit_wd, limit, #1 /* Limit != 0, so no underflow. */
lsr limit_wd, limit_wd, #4 /* Convert to Qwords. */
/* NUL detection works on the principle that (X - 1) & (~X) & 0x80
(=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
can be done in parallel across the entire word. */
@ -107,7 +109,7 @@ def_fn strnlen
bic has_nul2, tmp3, tmp4
subs limit_wd, limit_wd, #1
orr tmp1, has_nul1, has_nul2
ccmp tmp1, #0, #0, ne /* NZCV = 0000 */
ccmp tmp1, #0, #0, pl /* NZCV = 0000 */
b.eq .Lloop
/* End of critical section -- keep to one 64Byte cache line. */
@ -145,23 +147,38 @@ def_fn strnlen
ret
.Lmisaligned:
add tmp3, limit, tmp1
/* Deal with a partial first word.
We're doing two things in parallel here;
1) Calculate the number of words (but avoiding overflow if
limit is near ULONG_MAX) - to do this we need to work out
limit + tmp1 - 1 as a 65-bit value before shifting it;
2) Load and mask the initial data words - we force the bytes
before the ones we are interested in to 0xff - this ensures
early bytes will not hit any zero detection. */
sub limit_wd, limit, #1
neg tmp4, tmp1
cmp tmp1, #8
neg tmp1, tmp1
ldp data1, data2, [src], #16
add limit_wd, tmp3, #15
lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
mov tmp2, #~0
and tmp3, limit_wd, #15
lsr limit_wd, limit_wd, #4
mov tmp2, #~0
ldp data1, data2, [src], #16
lsl tmp4, tmp4, #3 /* Bytes beyond alignment -> bits. */
add tmp3, tmp3, tmp1
#ifdef __AARCH64EB__
/* Big-endian. Early bytes are at MSB. */
lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
lsl tmp2, tmp2, tmp4 /* Shift (tmp1 & 63). */
#else
/* Little-endian. Early bytes are at LSB. */
lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
lsr tmp2, tmp2, tmp4 /* Shift (tmp1 & 63). */
#endif
add limit_wd, limit_wd, tmp3, lsr #4
orr data1, data1, tmp2
orr data2a, data2, tmp2
csinv data1, data1, xzr, le
csel data2, data2, data2a, le
b .Lrealigned