Instead of doing mfctr, mflr, mftb, mtctr, mtlr as separate ops,
just pass down mfspr and mtspr ops with the spr number and let
execute1 decode which SPR we're addressing. This will help reduce
the number of instruction bits decode1 needs to look at.
In fact we now pass down the whole instruction from decode2 to
execute1. We will need more bits of the instruction in future,
and the tools should just optimize away any that we don't end
up using. Since the 'aa' bit was just a copy of an instruction
bit, we can now remove it from the record.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Hopefully it's not too timing catastrophic. The variable newcrf will
be handy for the other CR ops when we implement them I suspect.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This adds a divider unit, connected to the core in much the same way
that the multiplier unit is connected. The division algorithm is
very simple-minded, taking 64 clock cycles for any division (even
32-bit division instructions).
The decoding is simplified by making use of regularities in the
instruction encoding for div* and mod* instructions. Instead of
having PPC_* encodings from the first-stage decoder for each of the
different div* and mod* instructions, we now just have PPC_DIV and
PPC_MOD, and the inputs to the divider that indicate what sort of
division operation to do are derived from instruction word bits.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This module adds some simple core controls:
reset, stop, start, step
along with icache clear and reading the NIA and core
status bits
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org
We need to finish support for all the trap instructions, but for now
we at least need a decode entry for tw, so we know to stall until the
previous instruction completes. Some of our test cases were failing
because the trap executed before the previous instruction completed.
All these trap instructions need to be resolved at completion, not
in execute.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
We can force all existing code to use the UART console
by passing 0 in bit zero of the sim config register.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Handle the CR as a single field with per nibble enables. Forward any
writes in the same cycle.
If this proves to be an issue for timing, we may want to revisit
this in the future. For now, it keeps things simple.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Paul Mackerras
Benjamin Herrenschmidt