[libre-riscv-dev] [Bug 313] Create Branch Pipeline for POWER9

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Fri May 15 21:39:27 BST 2020


--- Comment #12 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
likewise we need LR at the same time.  yeah, i know.  it's a hell of a lot of
incoming wires and registers.

* LR 64-bit
* CIA 64-bit (48 probably more like?)
* CTR 64-bit
* TAR 64-bit
* CR 32-bit
* CompBROpSubset a *lot*.  around 64 bits due to the expanded decoding.

we just have to tolerate that, and have a *five* input Branch Computation Unit.

which has me slightly concerned for adding TRAP to the same pipeline, because
that brings in *another* 128 bits (!!) - RA 64-bit, RB 64-bit, plus it modifies
the CR so that's another 32 bits on the output side as well.  blegh.  can't do
new bugreport, there.

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