Bazel rules for GHDL

This repository contains a bazel rule set for running ghdl, the VHDL simulator and synthesizer.

Prerequisites

• bazel installation via bazelisk. I recommend downloading bazelisk and placing it somewhere in your $PATH under the name bazel.

Everything else will be downloaded for use the first time you run the build.

Documentation

See rules.md for the generated rule documentation.

Architecture & Integration with rules_vhdl

This workspace is fully integrated with the foundational rules_vhdl graph module. VHDL dependency graphs are declared once using vhdl_library, and the GHDL backend translates this metadata into compilation, elaboration, and test execution steps.

• vhdl_library (from @rules_vhdl): Groups VHDL source files and describes dependencies. It generates a transitive VHDLLibraryProvider.
• ghdl_analyze: Consumes vhdl_library targets and compiles VHDL files using ghdl -a into an isolated, hermetic GHDL object directory.
• ghdl_elaborate: Takes compiled GHDL object targets and elaborates them using ghdl -e.
• ghdl_test: Groups compilation, elaboration, and execution into an executable test rule using ghdl -r inside a sandboxed test runner.

Hermeticity

This rule set is completely hermetic. All dependencies are set up automatically by bazel. In addition, ghdl_analyze automatically rewrites absolute sandbox execution paths inside generated .cf library indexes into relative paths, enabling robust compilation across different sandboxed actions.

Examples

In general, see integration/ for example use.

The module is available through my bazel registry at https://github.com/filmil/bazel-registry.

Declaring a VHDL Library and Compile Target

load("@rules_vhdl//vhdl:defs.bzl", "vhdl_library")
load("@rules_ghdl//:rules.bzl", "ghdl_analyze")

# 1. Group the sources
vhdl_library(
    name = "lib_src",
    srcs = ["hello.vhdl"],
    library = "lib",
)

# 2. Analyze the library
ghdl_analyze(
    name = "lib",
    library = ":lib_src",
    args = ["--ieee=synopsys"],
)

Running VHDL Tests

load("@rules_ghdl//:rules.bzl", "ghdl_test")

ghdl_test(
    name = "hello_world_test",
    srcs = ["test.vhdl"],
    entity = "hello_world",
)

To run tests in the integration/ directory:

cd integration && bazel test //...

Notes

• Only Linux host and target are supported for now, although it should be straightforward (but not necessarily trivial) to add support for other archs.

References

• https://github.com/solsjo/rules_ghdl: an alternative rule set, which is not hermetic.