Fix DSim support

[akashlevy]

Continued from #2286:

This PR fixes up Ibex UVM support for DSim simulator. Several things had to be fixed:

• Simulator compatibility: DSim requires that enum values must use enum constants
  • Use ZERO enum constant instead of '0 and 0 for instr enums: dv/uvm/core_ibex/riscv_dv_extension/ibex_directed_instr_lib.sv
  • Add Ibex-specific CSRs (CPUCTRLSTS, SECURESEED) to privileged_reg_t and replace enum constants into implemented_csr[]: vendor/google_riscv-dv/src/riscv_instr_pkg.sv, vendor/google_riscv-dv/euvm/riscv/gen/riscv_instr_pkg.d, dv/uvm/core_ibex/riscv_dv_extension/riscv_core_setting.tpl.sv
• Simulator compatibility: DSim does not appear to respect "re-exports"
  • Replace all re-exported ibex_mem_intf_agent_pkg::ADDR_WIDTH and ibex_mem_intf_agent_pkg::DATA_WIDTH with ibex_mem_intf_pkg::ADDR_WIDTH and ibex_mem_intf_pkg::DATA_WIDTH: dv/uvm/core_ibex/tests/core_ibex_base_test.sv, dv/uvm/core_ibex/tests/core_ibex_test_lib.sv, dv/uvm/core_ibex/tests/core_ibex_vseq.sv
• Simulator compatibility: Unroll loops for 2D arrays to support DSim in rtl/ibex_core.sv
• Simulator compatibility: Add #0 to allow clock to properly start in dv/uvm/core_ibex/tb/core_ibex_tb_top.sv
• Script fix: Add co-simulation support for DSim in dv/uvm/core_ibex/yaml/rtl_simulation.yaml
• Script fix: Add DSim case for reloc_word in dv/uvm/core_ibex/scripts/run_instr_gen.py
• Script fix: Replace dsim_compile_opts with dsim_opts and apply correct defparams and +defines in util/ibex_config.py
• Misc. fix: PC mismatch should remove 64-bit sign extension when printing ISS PC dv/cosim/spike_cosim.cc

With these fixes, I was able to get most of the UVM tests running with SIMULATOR=dsim ITERATIONS=1:

82.14% PASS 46 PASSED, 10 FAILED

Future enhancements:

• Fix remaining DSim failures
• Coverage support for DSim
• Fix METADATA-DIR make variable issue
• Support testbench elaboration with Verific #2299

[akashlevy]

Also, I'll share my DSim setup in case you want to try it out. I'm not using DSim Desktop, I'm using the CLI binaries. You need both AltairDSim2025.0.1_linux64.bin and dsim-license.json, which can be obtained via the Altair downloads page.

Here's my DSim base Dockerfile:

# Use Ubuntu as base image (needs --platform=linux/amd64)
FROM ubuntu:22.04

# Set environment variables to avoid interactive prompts during installation
ENV DEBIAN_FRONTEND=noninteractive

# Create a directory for dsim
WORKDIR /root

# Install required dependencies
RUN apt-get update -y
RUN apt-get install -y build-essential ca-certificates libsqlite3-dev

# Copy the dsim binary
COPY AltairDSim2025.0.1_linux64.bin /root/
COPY dsim-license.json /root/

# Make the binary executable
RUN chmod +x /root/AltairDSim2025.0.1_linux64.bin

# Install dsim
RUN /root/AltairDSim2025.0.1_linux64.bin -i silent -DACCEPT_EULA=YES

# Remove dsim installer
RUN rm /root/AltairDSim2025.0.1_linux64.bin

# Setup dsim environment
ENV DSIM=dsim
ENV DSIM_HOME=/root/AltairDSim/2025
ENV DSIM_LICENSE=/root/dsim-license.json
ENV DSIM_LIB_PATH=${DSIM_HOME}/lib
ENV UVM_HOME=${DSIM_HOME}/uvm/1.2/
ENV STD_LIBS=${DSIM_HOME}/std_pkgs/lib
ENV RADFLEX_PATH=${DSIM_HOME}/radflex
ENV LLVM_HOME=${DSIM_HOME}/llvm_small
ENV PATH=${LLVM_HOME}/bin:${DSIM_HOME}/bin:$PATH
ENV LD_LIBRARY_PATH=${DSIM_HOME}/lib:${LLVM_HOME}/lib

# Symlink libuvm_dpi.so to dsim lib path
RUN ln -s ${UVM_HOME}/src/dpi/libuvm_dpi.so ${DSIM_LIB_PATH}/libuvm_dpi.so

# Command to run when container starts
CMD ["dsim"]

And here's my ibex Dockerfile, which builds on this:

# Use dsim as base image (needs --platform=linux/amd64)
FROM dsim

# Install required dependencies
RUN apt-get update -y
RUN apt-get install -y device-tree-compiler git pkg-config python3-pip vim wget

# Install required python dependencies
RUN pip3 install --upgrade pip
RUN pip3 install bitstring junit_xml mako pathlib3x portalocker pydantic typeguard typing_utils pyyaml

# Install ibex spike
RUN git clone -b ibex_cosim https://github.com/lowRISC/riscv-isa-sim.git riscv-isa-sim-cosim && \
    cd riscv-isa-sim-cosim && \
    mkdir build && cd build && \
    ../configure --enable-commitlog --enable-misaligned --prefix=/opt/spike-cosim && \
    make -j`nproc` install && \
    cd ../.. && \
    rm -rf riscv-isa-sim-cosim

# Install riscv toolchain
RUN wget https://github.com/lowRISC/lowrisc-toolchains/releases/download/20250611-1/lowrisc-toolchain-gcc-rv32imcb-x86_64-20250611-1.tar.xz && \
    tar xvf lowrisc-toolchain-gcc-rv32imcb-x86_64-20250611-1.tar.xz && \
    mv lowrisc-toolchain-gcc-rv32imcb-x86_64-20250611-1 /opt/riscv && \
    rm lowrisc-toolchain-gcc-rv32imcb-x86_64-20250611-1.tar.xz

# Environment setup
ENV RISCV_TOOLCHAIN=/opt/riscv
ENV RISCV_GCC=$RISCV_TOOLCHAIN/bin/riscv32-unknown-elf-gcc
ENV RISCV_OBJCOPY=$RISCV_TOOLCHAIN/bin/riscv32-unknown-elf-objcopy
ENV SPIKE_PATH=/opt/spike-cosim
ENV PKG_CONFIG_PATH=/opt/spike-cosim/lib/pkgconfig
ENV IBEX_ROOT=/root/ibex
ENV PRJ_DIR=/root/ibex
ENV LOWRISC_IP_DIR=/root/ibex/vendor/lowrisc_ip

[akashlevy]

Tagging @hcallahan-lowrisc for review

[hcallahan-lowrisc]

This is great, thanks!
Just one minor tweak, and I think this is ready to be merged.
If you could split the changes to rtl/ibex_core.sv out into a seperate commit that should be it, we try to keep RTL changes standalone in the history.

[akashlevy]

Done! 0314b58 has rtl/ibex_core.sv changes separated out now.

[hcallahan-lowrisc]

Thanks for your contribution @akashlevy! It's great to see DSim functional again, and very much appreciated.

[akashlevy]

Woo-hoo!