[Libre-soc-bugs] [Bug 324] create POWER9 DIV pipeline

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Fri Jun 19 21:22:14 BST 2020


--- Comment #29 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Luke Kenneth Casson Leighton from comment #27)
> if you want to make it "clearer", it should be called "POWER9_ne",
> and "POWER9_trunc_div" etc. however the reason we've not done this is
> because it makes the auto-generated code pretty much unreadable :)

That trunc_div function isn't intended to be Power ISA compatible (or POWER9,
which is not even what we're implementing -- we're implementing Libre-SOC's
first core -- not POWER9, they are different cpus -- please avoid calling the
Power ISA "POWER9", they are different things. That's like if AMD called their
hypothetical new processor core "Sandy Bridge" or "Pentium", which are widely
associated with Intel).

trunc_div is intended to be the equivalent of python's // operator, except that
it rounds differently -- the same way Rust, C, C++, Java, x86, and Power do.

Similarly with trunc_rem.

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