Demonstrates a practical workflow for large designs in a git repository that is not a fork of OpenROAD-flow-scripts and that is using its own file layout: similar to a private repository or a large project.
MegaBoom(a RISC-V SoC from Chipyard) has been chosen as a test-case as it is large, familiar and interesting in itself.
The build of MegaBoom takes on the order of 24 hours, unless you configure an artifact server to download pre-built results.
Read OpenROAD-flow-scripts for more details on how to use Bazel to build BoomTile and examine results, but oneliner to build BoomTile and view the results after the CTS(clock tree synthesis stage) in the GUI is:
bazel run BoomTile_cts $(pwd)/tmp gui_cts
For running Bazel flow for the ORFS, MegaBoom uses bazel-orfs. It provides two different Bazel flows for running Physical Design Flow with OpenROAD-flow-scripts. For the installation and usage guide, please refer to bazel-orfs's README.
Bazel-orfs must be specified in MegaBoom as the external dependency. It can be pinned to a specific revision of the upstream repository or the dependency can point to a local bazel-orfs workspace available on disk. Setup can be modified in MODULE.bazel file.
Based on: https://chipyard.readthedocs.io/en/stable/VLSI/Sky130-OpenROAD-Tutorial.html#initial-setup
Note: Chipyard main does not work smoothly with MegaBoom as of writing as Chipyard is mixing SFC and MFC.
Follow ucb-bar/chipyard#1623 for latest updates.
That said, the rtl/ folder was generated using latest Chipyard + some hacked files locally:
make tutorial=sky130-openroad CONFIG=MegaBoomMacroConfig verilog
Build everything:
./build-setup.sh --skip-ctags --skip-conda --skip-toolchain --skip-firesim --skip-marshal --skip-clean
Create Verilog code:
make CONFIG=MegaBoomConfig tech_name=asap7 VLSI_TOP=ChipTop INPUT_CONFS=example-asap7.yml TOP_MACROCOMPILER_MODE='--mode synflops' verilog
Here is some operational information to help you use megaboom.
If you only have a single Google account that you use for Google Cloud locally, you can use
--google_default_credentials.
If you are use multiple google accounts, using the default credentials can be cumbersome when
switching between projects. To avoid this, you can use the --credential_helper option
instead, and pass a script that fetches credentials for the account you want to use. This
account needs to have logged in using gcloud auth login and have access to the bucket
specified.
.bazelrc is under git version control and it will try to read in .user-bazelrc, which is
not under git version control, which means that for git checkout or rebase operations will
ignore the user configuration in .user-bazelrc.
Copy the snippet below into .user-bazelrc and specify your username by modifying # user: [email protected]:
# user: [email protected]
build --credential_helper=%workspace%/cred_helper.py --remote_cache=https://storage.googleapis.com/megaboom-bazel-artifacts --remote_cache_compression=true
cred_helper.py will parse .user-bazelrc and look for the username in the comment.
To test, run:
$ ./cred_helper.py test
Running: gcloud auth print-access-token [email protected]
{
"kind": "storage#testIamPermissionsResponse",
"permissions": [
"storage.buckets.get",
"storage.objects.create"
]
}
Note: To test the credential helper, make sure to restart Bazel to avoid using a previous cached authorization:
bazel shutdown
bazel build BoomTile_final_scripts
To gain access to the https://storage.googleapis.com/megaboom-bazel-artifacts bucket, reach out to Tom Spyrou, Precision Innovations (https://www.linkedin.com/in/tomspyrou/).
To update the orfs version that megaboom uses, update the image and sha256 in the orfs.default section of the MODULE.bazel file with the appropriate orfs-version-tag and orfs-version-sha256 values.
orfs.default(
image = "openroad/orfs:<orfs-version-tag>",
sha256 = "<orfs-version-sha256>",
)
The list of available orfs docker images can be found at the orfs Docker Hub.
After MODULE.bazel has been modified, execute the following command to update the MODULE.bazel.lock file:
bazel mod tidy
