As well as clarifying the logic in the main decode function (no
functionality change), this also fixes some cases that should be
illegal but weren't caught in the memory instructions.
The decode had a TODO to handle illegal instructions more precisely.
Some instructions in the new CHERI spec were not causing traps, and
seemed to wedge the core.
Switch to a new style where instructions are assumed illegal unless
explicitly declared legal.
This definitely at least covers many funct3 etc fields where only
some of the encodings are currently used.
This fixes a wedge in the frontend: the fetch stage could get stuck
in a loop, with the next address predictor deciding that the redirect
PC is a compressed instruction doing a close jump. On mispredict,
this would get retrained, but "mispedict" was denoted as an
untaken branch to PC+2. If unlucky, PC+2 could cross an alignment
boundary, causing the untaken branch to be interpreted as a long
branch, leaving an old competing entry in the compressed branch BTB,
which would then take priority.
Fix by always marking entries in both close and long BTBs when not
taken: to avoid hurting performance, this kind of update will not
insert into either BTB unless already present.
This means that two returns decoded in the same cycle are likely to result in a misprediction.
The trouble here was that the Decode loop wouldn't build with slight changes due to a scheduling conflict through the RAS due to the dependence of the next ras.first method on the earlier ras.pop method. This was indeed an unpleasant combinational path between concurrently decoding instructions. This change allows all RAS predictions to be independent (by assuming no pushes or pops occur earlier in the bundle than a return).
dmactive should only go low when the debug module has successfully
reset. Approximate this by waiting for 1024 cycles, allowing any
register access requests and system bus requests to come back.
This was probably removed for performance, but now that we have
a faster workaround for loading kernels on the DE10, we should
probably prioritise accurate error information instead.
Konata: change M to F3
Added konata support to ALU pipeline
Added KONATA support to Fpu pipeline
Added KONATA support to Mem pipeline
Finished v1 of KONATA support
Added improvements to catch fragments in Konata
Kill fragments that have been merged
Fixed order of konata logs
Added commit stage output
Ensured that only the Commit stage can retire instructions in konata
Fixed printing commit stage log for Cap instructions
Changed Kanata to include the cycle counter for each line in the log file; please note that this requires post processing
Added reservation station support for Konata
Added parsing script for Toooba output
Removed double updated to D stage
Adressed Peter's comments
The referenced commit did not merge well with our code base. Therefore, I copied over the changes manually. These changes do
not constitute a working Konata support for Toooba. In this commit, I commented out some things that did not compile, which will be fixed in future
use it only in the L1 caches so that the L2 cache can have lower
resource utilisation and better timing. (Resource utilisation is up
about 5% with the new design, and it's not necessary for the L2 cache.)
