diff options
| author | Marcus Shawcroft <marcus.shawcroft@arm.com> | 2013-01-17 18:52:37 +0400 |
|---|---|---|
| committer | Marcus Shawcroft <marcus.shawcroft@arm.com> | 2013-01-17 18:52:37 +0400 |
| commit | 78f66de6ce7a7128ab716f2b94ba98c138cf3153 (patch) | |
| tree | ab94462a7aae03fcd6d5c7992f536cc71df15fb7 /newlib | |
| parent | 211dd84b838e17901221067742438a9f7e4c3669 (diff) | |
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.
Diffstat (limited to 'newlib')
| -rw-r--r-- | newlib/ChangeLog | 6 | ||||
| -rw-r--r-- | newlib/libc/machine/aarch64/strnlen.S | 39 |
2 files changed, 34 insertions, 11 deletions
diff --git a/newlib/ChangeLog b/newlib/ChangeLog index 941077974..15123c0fc 100644 --- a/newlib/ChangeLog +++ b/newlib/ChangeLog @@ -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 diff --git a/newlib/libc/machine/aarch64/strnlen.S b/newlib/libc/machine/aarch64/strnlen.S index 893163d90..c255c3f7c 100644 --- a/newlib/libc/machine/aarch64/strnlen.S +++ b/newlib/libc/machine/aarch64/strnlen.S @@ -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 |