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| author | Alan Modra <amodra@gmail.com> | 2013-08-17 18:40:11 +0930 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2013-10-04 10:39:32 +0930 |
| commit | db9b4570c5dc550074140ac1d1677077fba29a26 (patch) | |
| tree | c6469b8ce6b7ec28cc9f7c27484e67d351ce3349 /sysdeps/powerpc/powerpc64/power7 | |
| parent | f7c399cff5bd04ee9dc117fb6b0f39597dc047c6 (diff) | |
| download | glibc-db9b4570c5dc550074140ac1d1677077fba29a26.zip glibc-db9b4570c5dc550074140ac1d1677077fba29a26.tar.gz glibc-db9b4570c5dc550074140ac1d1677077fba29a26.tar.bz2 | |
PowerPC LE strlen
http://sourceware.org/ml/libc-alpha/2013-08/msg00097.html
This is the first of nine patches adding little-endian support to the
existing optimised string and memory functions. I did spend some
time with a power7 simulator looking at cycle by cycle behaviour for
memchr, but most of these patches have not been run on cpu simulators
to check that we are going as fast as possible. I'm sure PowerPC can
do better. However, the little-endian support mostly leaves main
loops unchanged, so I'm banking on previous authors having done a
good job on big-endian.. As with most code you stare at long enough,
I found some improvements for big-endian too.
Little-endian support for strlen. Like most of the string functions,
I leave the main word or multiple-word loops substantially unchanged,
just needing to modify the tail.
Removing the branch in the power7 functions is just a tidy. .align
produces a branch anyway. Modifying regs in the non-power7 functions
is to suit the new little-endian tail.
* sysdeps/powerpc/powerpc64/power7/strlen.S (strlen): Add little-endian
support. Don't branch over align.
* sysdeps/powerpc/powerpc32/power7/strlen.S: Likewise.
* sysdeps/powerpc/powerpc64/strlen.S (strlen): Add little-endian support.
Rearrange tmp reg use to suit. Comment.
* sysdeps/powerpc/powerpc32/strlen.S: Likewise.
Diffstat (limited to 'sysdeps/powerpc/powerpc64/power7')
| -rw-r--r-- | sysdeps/powerpc/powerpc64/power7/strlen.S | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/sysdeps/powerpc/powerpc64/power7/strlen.S b/sysdeps/powerpc/powerpc64/power7/strlen.S index 3432169..807ef10 100644 --- a/sysdeps/powerpc/powerpc64/power7/strlen.S +++ b/sysdeps/powerpc/powerpc64/power7/strlen.S @@ -30,7 +30,11 @@ ENTRY (strlen) with cmpb. */ li r5,-1 /* MASK = 0xffffffffffffffff. */ ld r12,0(r4) /* Load doubleword from memory. */ +#ifdef __LITTLE_ENDIAN__ + sld r5,r5,r6 +#else srd r5,r5,r6 /* MASK = MASK >> padding. */ +#endif orc r9,r12,r5 /* Mask bits that are not part of the string. */ cmpb r10,r9,r0 /* Check for null bytes in DWORD1. */ cmpdi cr7,r10,0 /* If r10 == 0, no null's have been found. */ @@ -48,9 +52,6 @@ ENTRY (strlen) cmpb r10,r12,r0 cmpdi cr7,r10,0 bne cr7,L(done) - b L(loop) /* We branch here (rather than falling through) - to skip the nops due to heavy alignment - of the loop below. */ /* Main loop to look for the end of the string. Since it's a small loop (< 8 instructions), align it to 32-bytes. */ @@ -87,9 +88,15 @@ L(loop): 0xff in the same position as the null byte in the original doubleword from the string. Use that to calculate the length. */ L(done): - cntlzd r0,r10 /* Count leading zeroes before the match. */ +#ifdef __LITTLE_ENDIAN__ + addi r9, r10, -1 /* Form a mask from trailing zeros. */ + andc r9, r9, r10 + popcntd r0, r9 /* Count the bits in the mask. */ +#else + cntlzd r0,r10 /* Count leading zeros before the match. */ +#endif subf r5,r3,r4 - srdi r0,r0,3 /* Convert leading zeroes to bytes. */ + srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */ add r3,r5,r0 /* Compute final length. */ blr END (strlen) |