Commit Graph

74 Commits (cc4dcb3597914bcf6730cdbabc7fbe3605c80c94)

Author SHA1 Message Date
Paul Mackerras 58b06eb5f3 decode: Remove const fields from decode_rom_t
The const* fields of decode_rom_t drove multiplexers in decode2 that
picked out various instruction fields and put them into the const*
fields of the Decode2ToExecute1Type record, from where they were
used in execute1.  However, the code in execute1 can just as easily
use the appropriate fields of the original instruction word, since
that is now available in execute1.  This therefore changes the
code to do that, resulting in smaller decode tables.

Suggested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
Paul Mackerras 143d0ae9e4 decode: Fix larx/stcx instructions to use RA_OR_ZERO not RA
The l?arx and st?cx. instructions are defined to use the normal indexed
mode address calculations, i.e. (RA|0) + RB.  Fix their entries in the
decode table to say RA_OR_ZERO rather than RA.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
Paul Mackerras bbae2d1eda decode: Index minor op table with insn bits for opcode 31
This changes decode_op_31_array from being indexed by a ppc_insn_t
(which is derived from the instruction word by a whole series of
if/elsif statements) to being indexed directly by bits 10...1 of
the instruction word.  With this we no longer need ppc_insn.

This then means that the decode1 stage doesn't distinguish between
mfcr and mfocrf, or between mtcrf and mtocrf, since those are
distinguished by the value in bit 20 of the instruction.  To
accommodate that, execute1 changes so that the one op value (OP_MFCR)
does either the mfcr or the mfocrf behaviour depending on bit 20
of the instruction word; and similarly for mtcrf/mtocrf.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
Paul Mackerras 21d3f8a5ed decode: Index minor op table with insn bits for opcode 30
This comprises the 64-bit rotate and mask instructions.  In order to
reduce the table index to 3 bits, we combine rldcl and rdlcr into a
single op (OP_RLDCX), and choose the right mask at execute time based
on bit 1 of the instruction word.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
Paul Mackerras 00e9f801f6 decode: Index minor op table with insn bits for opcode 19
This changes the decoding of major opcode 19 from using the ppc_insn_t
index to using bits of the instruction word directly.  Opcode 19 has
a 10-bit minor opcode field (bits 10..1) but the space is sparsely
filled.  Therefore we index a table of single-bit entries with the
10-bit minor opcode to filter out the illegal minor opcodes, and
index a table using just 3 bits -- 5, 3 and 2 -- of the instruction
to get the decode entry.  This groups together all the instructions
in 4 columns of the opcode map as a single entry.  That means that
mcrf and all the CR logical ops get grouped together, and bcctr, bclr
and bctar get grouped together.  At present the CR logical ops are not
implemented, so their grouping has no impact.

The code for bclr and bcctr in execute1 is now common, using a single
op, and it now determines the branch address by looking at bit 10 of
the instruction word at execute time.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
Paul Mackerras e30a87593a decode: Start moving towards decoding by major opcode first
With this, we have a table for most major opcodes and separate
tables for each major opcode that has further decoding required.
These tables are still mostly indexed by the ppc_insn_t values,
however.

A few things are still decoded completely at the top level: nop,
attn and sim_config.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
5 years ago
Paul Mackerras c9e92483b8 decode: Push mtspr/mfspr register decoding down into execute1
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>
5 years ago
Benjamin Herrenschmidt 3e6f656a90 Add MCRF instruction
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>
5 years ago
Benjamin Herrenschmidt 554ae88540 Implement absolute branches
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Anton Blanchard b57325ce29 Merge branch 'divider' of https://github.com/paulusmack/microwatt 5 years ago
Anton Blanchard 5a6f8d26d1 Rename OP_SUBFC -> OP_SUBFE, OP_ADDC -> OP_ADDE
These were somewhat badly named.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Paul Mackerras d5bc6c8824 Add a divider unit and a testbench for it
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>
5 years ago
Benjamin Herrenschmidt 98f0994698 Add core debug module
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
5 years ago
Anton Blanchard 7bb88d5321
Merge pull request #59 from antonblanchard/trap-decode
Fix make check
5 years ago
Anton Blanchard 427effdaa9 Fix make check
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>
5 years ago
Anton Blanchard 9867fb6149 Add a decode for the nop instruction
We want these to go out without any GPR dependencies, so add
a specific entry in decode for them.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Anton Blanchard acdb2ea157 No need to gate nia or insn in decode1
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Anton Blanchard b9e28598b4 Explicitly check against '1' in if statements
nvc doesn't like what I think is a VHDL 2008 construct. Lets just
check against '1' explicitly.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Anton Blanchard a2df2a10a2 Remove sim console
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>
5 years ago
Anton Blanchard 92a7152370 Rework pipeline, add stall and flush signals
This adds stall and flush signals to the pipeline.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Anton Blanchard 9687034d78 Add a decode bit to mark an instruction as single through the pipeline
This is used by the pipelining patches. Mark everyone as single through
the pipeline to start.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Benjamin Herrenschmidt b0ade2857f decode1 array fix header
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Anton Blanchard 9fbaea6f08 Rework CR file and add forwarding
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>
5 years ago
Anton Blanchard 5a29cb4699 Initial import of microwatt
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago