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Paul Mackerras
d2ca625b3b
This handles OP_CMP like a subtraction; the main adder computes ~RA + RB + 1, and the condition codes are computed from the results. A direct comparison of the two input operands is used to calculate the EQ bit of the condition result. The LT and GT bits are computed from the MSB of the subtraction result, the carry out from the subtraction, and the MSBs of the operands. For a 32-bit comparison, the 32-bit carry and bit 31 of the result and input operands are used; for a 64-bit comparison, the 64-bit carry and bit 63 of the operands and result are used. It turns out to be more convenient to use the 'signed' field of the decode table to distinguish signed from unsigned comparisons, rather than the insn_type. Therefore this uses OP_CMP for both cmp and cmpl, which also has the benefit of reducing the number of values in insn_type_t. Doing this saves over 200 slice LUTs on the Arty A7-100 and improves timing slightly as well. Signed-off-by: Paul Mackerras <paulus@ozlabs.org> |
4 years ago | |
|---|---|---|
| fpga | 4 years ago | |
| hello_world | 4 years ago | |
| media | 5 years ago | |
| scripts | 4 years ago | |
| sim-unisim | 5 years ago | |
| tests | 4 years ago | |
| .gitignore | 5 years ago | |
| .travis.yml | 5 years ago | |
| LICENSE | 5 years ago | |
| Makefile | 4 years ago | |
| README.md | 4 years ago | |
| cache_ram.vhdl | 5 years ago | |
| common.vhdl | 4 years ago | |
| control.vhdl | 4 years ago | |
| core.vhdl | 4 years ago | |
| core_debug.vhdl | 5 years ago | |
| core_tb.vhdl | 5 years ago | |
| countzero.vhdl | 5 years ago | |
| countzero_tb.vhdl | 5 years ago | |
| cr_file.vhdl | 4 years ago | |
| cr_hazard.vhdl | 4 years ago | |
| crhelpers.vhdl | 5 years ago | |
| dcache.vhdl | 4 years ago | |
| dcache_tb.vhdl | 5 years ago | |
| decode1.vhdl | 4 years ago | |
| decode2.vhdl | 4 years ago | |
| decode_types.vhdl | 4 years ago | |
| divider.vhdl | 4 years ago | |
| divider_tb.vhdl | 4 years ago | |
| dmi_dtm_dummy.vhdl | 5 years ago | |
| dmi_dtm_tb.vhdl | 5 years ago | |
| dmi_dtm_xilinx.vhdl | 5 years ago | |
| execute1.vhdl | 4 years ago | |
| fetch1.vhdl | 5 years ago | |
| fetch2.vhdl | 5 years ago | |
| glibc_random.vhdl | 5 years ago | |
| glibc_random_helpers.vhdl | 5 years ago | |
| gpr_hazard.vhdl | 4 years ago | |
| helpers.vhdl | 4 years ago | |
| icache.vhdl | 4 years ago | |
| icache_tb.vhdl | 5 years ago | |
| icache_test.bin | 5 years ago | |
| insn_helpers.vhdl | 4 years ago | |
| loadstore1.vhdl | 4 years ago | |
| logical.vhdl | 5 years ago | |
| microwatt.core | 5 years ago | |
| multiply.vhdl | 4 years ago | |
| multiply_tb.vhdl | 4 years ago | |
| plru.vhdl | 5 years ago | |
| plru_tb.vhdl | 5 years ago | |
| ppc_fx_insns.vhdl | 4 years ago | |
| register_file.vhdl | 4 years ago | |
| rotator.vhdl | 5 years ago | |
| rotator_tb.vhdl | 5 years ago | |
| sim_bram.vhdl | 5 years ago | |
| sim_bram_helpers.vhdl | 5 years ago | |
| sim_bram_helpers_c.c | 5 years ago | |
| sim_console.vhdl | 5 years ago | |
| sim_console_c.c | 5 years ago | |
| sim_jtag.vhdl | 5 years ago | |
| sim_jtag_socket.vhdl | 5 years ago | |
| sim_jtag_socket_c.c | 5 years ago | |
| sim_uart.vhdl | 5 years ago | |
| soc.vhdl | 4 years ago | |
| utils.vhdl | 5 years ago | |
| wishbone_arbiter.vhdl | 5 years ago | |
| wishbone_bram_tb.bin | 5 years ago | |
| wishbone_bram_tb.vhdl | 5 years ago | |
| wishbone_bram_wrapper.vhdl | 5 years ago | |
| wishbone_debug_master.vhdl | 5 years ago | |
| wishbone_types.vhdl | 5 years ago | |
| writeback.vhdl | 4 years ago | |
README.md
Microwatt
A tiny Open POWER ISA softcore written in VHDL 2008. It aims to be simple and easy to understand.
Simulation using ghdl
You can try out Microwatt/Micropython without hardware by using the ghdl simulator. If you want to build directly for a hardware target board, see below.
- Build micropython. If you aren't building on a ppc64le box you will need a cross compiler. If it isn't available on your distro grab the powerpc64le-power8 toolchain from https://toolchains.bootlin.com
git clone https://github.com/micropython/micropython.git
cd micropython
cd ports/powerpc
make -j$(nproc)
cd ../../../
- Microwatt uses ghdl for simulation. Either install this from your distro or build it. Next build microwatt:
git clone https://github.com/antonblanchard/microwatt
cd microwatt
make
- Link in the micropython image:
ln -s ../micropython/ports/powerpc/build/firmware.bin main_ram.bin
- Now run microwatt, sending debug output to /dev/null:
./core_tb > /dev/null
Synthesis on Xilinx FPGAs using Vivado
-
Install Vivado (I'm using the free 2019.1 webpack edition).
-
Setup Vivado paths:
source /opt/Xilinx/Vivado/2019.1/settings64.sh
- Install FuseSoC:
pip3 install --user -U fusesoc
Fedora users can get FuseSoC package via
sudo dnf copr enable sharkcz/danny
sudo dnf install fusesoc
- Create a working directory and point FuseSoC at microwatt:
mkdir microwatt-fusesoc
cd microwatt-fusesoc
fusesoc library add microwatt /path/to/microwatt/
- Build using FuseSoC. For hello world (Replace nexys_video with your FPGA board such as --target=arty_a7-100):
fusesoc run --target=nexys_video microwatt --memory_size=8192 --ram_init_file=/path/to/microwatt/fpga/hello_world.hex
You should then be able to see output via the serial port of the board (/dev/ttyUSB1, 115200 for example assuming standard clock speeds). There is a know bug where initial output may not be sent - try the reset (not programming button on your board if you don't see anything.
- To build micropython (currently requires 1MB of BRAM eg an Artix-7 A200):
fusesoc run --target=nexys_video microwatt
Testing
- A simple test suite containing random execution test cases and a couple of micropython test cases can be run with:
make -j$(nproc) check
Issues
This is functional, but very simple. We still have quite a lot to do:
- There are a few instructions still to be implemented
- Need to add caches and bypassing (in progress)
- Need to add supervisor state (in progress)