ni...@lysator.liu.se (Niels Möller) writes:
L(top):
mov (ap, n, 8), %rdx
mulx %r8, alo, hi
adox ahi, alo
mov hi, ahi C 2-way unroll.
adox zero, ahi C Clears O
mov (bp, n), %rdx
mulx %r9, blo, hi
adox bhi, blo
mov hi, bhi
adox zero, bhi C clears O
adc blo, alo C Or sbb, for addsubmul_1msb0
mov alo, (rp, n, 8)
inc n
jnz top
Problem: the adc will write a useless value to the O flag. That is then
read by the first adox, yielding incorrect results. Clearing O without
creating any (too bad false) dependencies could perhaps be done with an
additional dummy adox zero, zero.
Another remedy would be to use adcx instead of adc, but then we cannot
easily make a addsubmul_1msb0 variant.
--
Torbjörn
Please encrypt, key id 0xC8601622
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