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

* libc/machine/aarch64/strncmp.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 14:53:32 +00:00
parent 78f66de6ce
commit 450fe1bfa3
2 changed files with 25 additions and 12 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/strncmp.S: Correct arithmetic for
argument N values close to the maximum representable
value in an unsigned 64 bit value.
2013-01-17 Marcus Shawcroft <marcus.shawcroft@linaro.org>
* libc/machine/aarch64/strnlen.S: Correct arithmetic for

31
newlib/libc/machine/aarch64/strncmp.S
View File

@ -81,8 +81,10 @@ def_fn strncmp
b.ne .Lmisaligned8
ands tmp1, src1, #7
b.ne .Lmutual_align
add limit_wd, limit, #7
lsr limit_wd, limit_wd, #3
/* Calculate the number of full and partial words -1. */
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
/* 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. */
@ -95,14 +97,14 @@ def_fn strncmp
sub tmp1, data1, zeroones
orr tmp2, data1, #REP8_7f
eor diff, data1, data2 /* Non-zero if differences found. */
csinv endloop, diff, xzr, ne /* Last Dword or differences. */
csinv endloop, diff, xzr, pl /* Last Dword or differences. */
bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
ccmp endloop, #0, #0, eq
b.eq .Lloop_aligned
/* End of performance-critical section -- one 64B cache line. */
/* Not reached the limit, must have found the end or a diff. */
cbnz limit_wd, .Lnot_limit
tbz limit_wd, #63, .Lnot_limit
/* Limit % 8 == 0 => all bytes significant. */
ands limit, limit, #7
@ -177,26 +179,31 @@ def_fn strncmp
.Lmutual_align:
/* Sources are mutually aligned, but are not currently at an
alignment boundary. Round down the addresses and then mask off
the bytes that precede the start point. */
the bytes that precede the start point.
We also need to adjust the limit calculations, but without
overflowing if the limit is near ULONG_MAX. */
bic src1, src1, #7
bic src2, src2, #7
add limit, limit, tmp1 /* Adjust the limit for the extra. */
lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
ldr data1, [src1], #8
neg tmp1, tmp1 /* Bits to alignment -64. */
neg tmp3, tmp1, lsl #3 /* 64 - bits(bytes beyond align). */
ldr data2, [src2], #8
mov tmp2, #~0
sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
#ifdef __AARCH64EB__
/* Big-endian. Early bytes are at MSB. */
lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
lsl tmp2, tmp2, tmp3 /* Shift (tmp1 & 63). */
#else
/* Little-endian. Early bytes are at LSB. */
lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
lsr tmp2, tmp2, tmp3 /* Shift (tmp1 & 63). */
#endif
add limit_wd, limit, #7
and tmp3, limit_wd, #7
lsr limit_wd, limit_wd, #3
/* Adjust the limit. Only low 3 bits used, so overflow irrelevant. */
add limit, limit, tmp1
add tmp3, tmp3, tmp1
orr data1, data1, tmp2
orr data2, data2, tmp2
lsr limit_wd, limit_wd, #3
add limit_wd, limit_wd, tmp3, lsr #3
b .Lstart_realigned
.Lret0: