| commit | e0066c59e40643f1a556a1336fbb21bc13a30a52 | [log] [tgz] |
|---|---|---|
| author | Rupert Swarbrick <rswarbrick@lowrisc.org> | Wed Jan 06 17:19:36 2021 +0000 |
| committer | Rupert Swarbrick <rswarbrick@gmail.com> | Fri Jan 15 09:25:36 2021 +0000 |
| tree | 6f37b3bbe07ad1efd3887819a039ccdb249124ec | |
| parent | c90e0c58a98990c1fc667f558c05db6367d5cc37 [diff] |
[otbn] Teach RIG to generate BEQ and BNE instructions The branching program flow means that we have to teach the RIG some new tricks. Firstly, we need to add "recursive" generation (so that the generator for a branch can generate stuff in each side below it). We do this by passing a continuation of type GenCont to the generator. Secondly, we need to tighten up the snippet type a bit. Branches are represented as branches in the expression tree (as you'd expect), and we also needed to add a sequencing type, SeqSnippet (so that you can have a list of instructions followed by a branch, for example). We always generate branches that converge (so there will only ever be one ECALL in the generated program). To glue the branches back together, we generate a jump from the end of one to the end of the other. This needs slight changes in the Jump generator so that we can specify the target address that we want in this case. The final big change is that we need to add support for "φ nodes" to the model, to cope with when execution joins back together. This is the "merge" method added to Model, CallStack and KnownMem. Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
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