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| author | Richard Henderson <rth@twiddle.net> | 2011-05-06 15:50:07 -0700 |
|---|---|---|
| committer | Richard Henderson <rth@twiddle.net> | 2011-05-06 15:50:07 -0700 |
| commit | 45a30cd864c313b353f47c8186b2b932069af4a1 (patch) | |
| tree | 8eb31dfd2bf4c7fbc4f613dcf604eb636c167ff8 /strlen.S | |
| parent | 87fb8be28570645cd42f940ebdaed4ee1d7724cf (diff) | |
| download | qemu-palcode-45a30cd864c313b353f47c8186b2b932069af4a1.zip qemu-palcode-45a30cd864c313b353f47c8186b2b932069af4a1.tar.gz qemu-palcode-45a30cd864c313b353f47c8186b2b932069af4a1.tar.bz2 | |
Handle padding in printf numerical output.
Diffstat (limited to 'strlen.S')
| -rw-r--r-- | strlen.S | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/strlen.S b/strlen.S new file mode 100644 index 0000000..5a77d72 --- /dev/null +++ b/strlen.S @@ -0,0 +1,59 @@ +/* + * strlen.S (c) 1995 David Mosberger (davidm@cs.arizona.edu) + * + * Finds length of a 0-terminated string. Optimized for the + * Alpha architecture: + * + * - memory accessed as aligned quadwords only + * - uses bcmpge to compare 8 bytes in parallel + * - does binary search to find 0 byte in last + * quadword (HAKMEM needed 12 instructions to + * do this instead of the 9 instructions that + * binary search needs). + */ + + .set noreorder + .set noat + + .align 3 + + .globl strlen + .ent strlen +strlen: + .frame $sp, 0, $26, 0 + .prologue 0 + + ldq_u $1, 0($16) # load first quadword ($16 may be misaligned) + lda $2, -1($31) + insqh $2, $16, $2 + andnot $16, 7, $0 + or $2, $1, $1 + cmpbge $31, $1, $2 # $2 <- bitmask: bit i == 1 <==> i-th byte == 0 + bne $2, found + +loop: ldq $1, 8($0) + addq $0, 8, $0 # addr += 8 + nop # helps dual issue last two insns + cmpbge $31, $1, $2 + beq $2, loop + +found: blbs $2, done # make aligned case fast + negq $2, $3 + and $2, $3, $2 + + and $2, 0x0f, $1 + addq $0, 4, $3 + cmoveq $1, $3, $0 + + and $2, 0x33, $1 + addq $0, 2, $3 + cmoveq $1, $3, $0 + + and $2, 0x55, $1 + addq $0, 1, $3 + cmoveq $1, $3, $0 + +done: subq $0, $16, $0 + ret $31, ($26) + + .end strlen |