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>
To match our one stage execute.
This might change back if we end up adding 2 stages to match the
LSU, but in that case we'll want forwards as well.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Anything that isn't a load or store and anything that doesn't read the
CR can go as soon as its inputs are ready.
While we could also allow SPR read/write and carry read/write, we plan
to change them to be read in decode2 and written in writeback soon and
they will need separate hazard detection to be added.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Check GPRs against any writers in the pipeline.
All instructions are still marked single in pipeline at
this stage.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Benjamin Herrenschmidt