Commit Graph

8 Commits (a750365ffa5f07046256d2824520817a6f704214)

Author SHA1 Message Date
Anton Blanchard 7994b98404 Fix some whitespace issues
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
3 years ago
Paul Mackerras 8edfbf638b core: Implement the cmpeqb and cmprb instructions
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
Paul Mackerras 6687aae4d6 core: Implement a simple branch predictor
This implements a simple branch predictor in the decode1 stage.  If it
sees that the instruction is b or bc and the branch is predicted to be
taken, it sends a flush and redirect upstream (to icache and fetch1)
to redirect fetching to the branch target.  The prediction is sent
downstream with the branch instruction, and execute1 now only sends
a flush/redirect upstream if the prediction was wrong.  Unconditional
branches are always predicted to be taken, and conditional branches
are predicted to be taken if and only if the offset is negative.
Branches that take the branch address from a register (bclr, bcctr)
are predicted not taken, as we don't have any way to predict the
branch address.

Since we can now have a mflr being executed immediately after a bl
or bcl, we now track the update to LR in the hazard tracker, using
the second write register field that is used to track RA updates for
update-form loads and stores.

For those branches that update LR but don't write any other result
(i.e. that don't decrementer CTR), we now write back LR in the same
cycle as the instruction rather than taking a second cycle for the
LR writeback.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
Benjamin Herrenschmidt e4f475e17f sprs: Store common SPRs in register file
This stores the most common SPRs in the register file.

This includes CTR and LR and a not yet final list of others.

The register file is set to 64 entries for now. Specific types
are defined that can represent a GPR index (gpr_index_t) or
a GPR/SPR index (gspr_index_t) along with conversion functions
between the two.

On order to deal with some forms of branch updating both LR and
CTR, we introduced a delayed update of LR after a branch link.

Note: We currently stall the pipeline on such a delayed branch,
but we could avoid stalling fetch in that specific case as we
know we have a branch delay. We could also limit that to the
specific case where we need to update both CTR and LR.

This allows us to make bcreg, mtspr and mfspr pipelined. decode1
will automatically force the single issue flag on mfspr/mtspr to
a "slow" SPR.

[paulus@ozlabs.org - fix direction of decode2.stall_in]

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
Paul Mackerras ec9b27660f execute: Copy XER[SO] to CR for cmp[i] and cmpl[i] instructions
We were copying in XER[SO] for the dot-form instructions but not the
explicit compare instructions.  Fix this.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
4 years ago
Benjamin Herrenschmidt 554ae88540 Implement absolute branches
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
4 years ago
Michael Neuling 4d5abfb430 Remove dynamic ranges from code
Some VHDL compilers like verific [1] don't like these, so let's remove
them. Lots of random code changes, but passes make check.

Also add basic script to run verific and generate verilog.

1. https://www.verific.com/

Signed-off-by: Michael Neuling <mikey@neuling.org>
5 years ago
Anton Blanchard 5a29cb4699 Initial import of microwatt
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago