Fix hwacha to match new RoCC FPU interface

ucb-bar / hwacha

Microarchitecture implementation of the decoupled vector-fetch accelerator

http://hwacha.org/

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Fix hwacha to match new RoCC FPU interface #5

Closed zhemao closed 7 years ago

zhemao commented 8 years ago

This changes Hwacha to match the new FPU interface in the rocket PR. The scalar fpu interface is greatly simplified since we no longer need to fully decode the signals and recode the floats. The one complication is that we need to convert between half-precision and single-precision if necessary.

aswaterman commented 8 years ago

If Hwacha is to use RoCC, then Hwacha's CP should share Hwacha's FP units, not Rocket's. Sharing Rocket's units is gonna have to be a non-standard thing.

aswaterman commented 8 years ago

Yunsup, Krste, and I discussed this some more, and came to the following conclusions:

Sharing the functional units is to improve QoR, not to make it easier to write RoCC accelerators.
Sharing anything significantly constrains the scalar microarchitecture.
As a consequence of the first two, it makes sense to share only the expensive units (i.e., FMA, divide, sqrt).
Even so, the interface is not considered a public API and may change over time.

We can talk about it more Monday.

colinschmidt commented 7 years ago

This was fixed sometime ago