[Libre-soc-dev] daily kan-ban update 18jun2021

[Luke Kenneth Casson Leighton]

On 6/18/21, Tobias Platen <libre-soc at platen-software.de> wrote:
 which I
> recently uncommented is throwing an exception, so my next step might be
> getting exceptions work in those unit tests.

it needs TestIssuer to pay attention to the exception.happened flag
and to set the address as appropriate.

this is slightly different from TRAP because where TRAP is an
immediate (combinatorial) illegal occurrence, LDST exceptions the LDST
has to run BEFORE the exception can even be thrown.

illegal instructions:

* decode
* detect
* TRAP

dead simple.

LD/ST:

* decode
* detect LDST
* RUN LDST
* LDST finishes execution and its result says "exception" (not, "LDST
was actioned")
* TestIssuer notes that
* drops exception flags into PowerDecoder2
* RE-RUNS THE DECODER
* decoder notes exception
* TRAP occurs *AT SAME PC AS LDST*

this "detection" part has *not* been implemented in the TestIssuer FSM, yet.

Cesar is going to be working on it, after we are confident that
LDSTCompUnit is working.

presently there is a bug in the LDSTCompUnit where it does not reset
properly after raising an exception.

l.