Re: Branch prediction hints in an ISA

  zs@ender.cs.mu.oz.au (Zoltan Somogyi) writes:
>Absolutely; with most modern machines, one wants to minimize the
>number of taken branches, whether the branch is predicted or not.
>
>However, there are occasions where you cannot follow this piece of
>advice. One such sitation is where a basic block ends with a
>conditional branch to its own start; putting a basic block *after*
>itself is pretty tough :-)


That's simple: just put a copy of the basic block there. Of course,
after applying this a few times, you might want to introduce a jump to
the original copy; but with n copies you have converted n-1
conditional branches to fall-through branches. Of course, if you look
at the I-Cache working set size (as Eric Corry mentioned), this code
replication is not helpful in this case.


- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html

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