[Sparc] Optimize compare instruction (#167140)
If we need to compare the result of a computation with 0, we can
sometimes replace the last instruction in the computation with one that
sets the integer condition codes. We can then branch immediately based
on the zero-flag instead of having to use an extra compare instruction
(a SUBcc instruction).
This is only possible if the result of the compare is not used anywhere
else and that no other instruction modifies the integer condition codes
between the time the result of the computation is defined and the time
it is used.
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Co-authored-by: Daniel Cederman <cederman@gaisler.com>
