Bump Bazel version to 8.3.1, migrate to bzlmod and bump LLVM to latest

.bazelrc

@@ -1,3 +1,4 @@
+common --enable_bzlmod
 common --action_env=BAZEL_CXXOPTS=-std=c++17
 common --cxxopt='-std=c++17'
 common --deleted_packages=externals

.bazelversion

@@ -1 +1 @@
-6.4.0
+8.3.1

.github/workflows/build_and_test.yml

@@ -19,10 +19,10 @@ jobs:
         with:
           path: |
             ~/.cache/bazel
-          # add import_llvm.bzl so that a new build occurs after an LLVM commit hash update
-          key: ${{ runner.os }}-bazel-${{ hashFiles('bazel/import_llvm.bzl') }}-${{ hashFiles('.bazelversion', '.bazelrc', 'WORKSPACE') }}
+          # add extensions.bzl so that a new build occurs after an LLVM commit hash update
+          key: ${{ runner.os }}-bazel-${{ hashFiles('extensions.bzl') }}-${{ hashFiles('.bazelversion', '.bazelrc', 'MODULE.bazel') }}
           restore-keys: |
-            ${{ runner.os }}-bazel-${{ hashFiles('bazel/import_llvm.bzl') }}
+            ${{ runner.os }}-bazel-${{ hashFiles('extensions.bzl') }}
 
       - name: "Run `bazel build`"
         run: |

.github/workflows/build_and_test_cmake.yml

@@ -27,15 +27,15 @@ jobs:
         with:
           path: |
             ./externals/llvm-project
-          key: ${{ runner.os }}-cmake-${{ hashFiles('bazel/import_llvm.bzl') }}-${{ hashFiles('**/CMakeLists.txt') }}
+          key: ${{ runner.os }}-cmake-${{ hashFiles('extensions.bzl') }}-${{ hashFiles('**/CMakeLists.txt') }}
 
       - name: Cache mlir-tutorial build
         id: cache-mlir-tutorial
         uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # pin@v4.2.3
         with:
           path: |
             ./build
-          key: ${{ runner.os }}-cmake-${{ hashFiles('bazel/import_llvm.bzl') }}-${{ hashFiles('**/CMakeLists.txt') }}
+          key: ${{ runner.os }}-cmake-${{ hashFiles('extensions.bzl') }}-${{ hashFiles('**/CMakeLists.txt') }}
 
       - name: Git config
         run: |
@@ -44,7 +44,7 @@ jobs:
       - name: Build LLVM
         if: steps.cache-llvm.outputs.cache-hit != 'true'
         run: |
-          LLVM_COMMIT=$(grep LLVM_COMMIT ${GITHUB_WORKSPACE}/bazel/import_llvm.bzl | head -n 1 | cut -d'"' -f 2 )
+          LLVM_COMMIT=$(grep 'commit = ' ${GITHUB_WORKSPACE}/extensions.bzl | head -n 1 | cut -d'"' -f 2)
           git submodule update --init --recursive
           cd externals/llvm-project
           git checkout ${LLVM_COMMIT}

.gitignore

@@ -3,6 +3,7 @@ bazel-bin
 bazel-mlir-tutorial
 bazel-out
 bazel-testlogs
+MODULE.bazel.lock
 
 # cmake related files
 # ignore the user specified CMake presets in subproject directories.

MODULE.bazel

@@ -0,0 +1,85 @@
+###############################################################################
+# Bazel now uses Bzlmod by default to manage external dependencies.
+# Please consider migrating your external dependencies from WORKSPACE to MODULE.bazel.
+#
+# For more details, please check https://github.com/bazelbuild/bazel/issues/18958
+###############################################################################
+
+module(
+    name = "mlir_tutorial",
+    version = "1.0.0",
+    repo_name = "mlir_tutorial",
+)
+
+# Dependencies available in BCR
+bazel_dep(name = "bazel_skylib", version = "1.7.1")
+bazel_dep(name = "rules_python", version = "1.2.0")
+bazel_dep(name = "platforms", version = "0.0.11")
+bazel_dep(name = "rules_cc", version = "0.1.1")
+bazel_dep(name = "rules_java", version = "8.12.0")
+bazel_dep(name = "protobuf", version = "30.1")
+bazel_dep(name = "rules_proto", version = "7.1.0")
+bazel_dep(name = "rules_pkg", version = "1.1.0")
+bazel_dep(name = "re2", version = "2024-07-02.bcr.1")
+bazel_dep(name = "abseil-cpp", version = "20250512.1")
+bazel_dep(name = "or-tools", version = "9.12")
+bazel_dep(name = "eigen", version = "4.0.0-20241125.bcr.2")
+bazel_dep(name = "highs", version = "1.11.0")
+bazel_dep(name = "pcre2", version = "10.46-DEV")
+bazel_dep(name = "glpk", version = "5.0.bcr.4")
+bazel_dep(name = "bliss", version = "0.73")
+bazel_dep(name = "scip", version = "9.2.0.bcr.3")
+bazel_dep(name = "zlib-ng", version = "2.0.7")
+
+# Hedron's Compile Commands Extractor for Bazel
+# https://github.com/hedronvision/bazel-compile-commands-extractor
+bazel_dep(name = "hedron_compile_commands", dev_dependency = True)
+git_override(
+    module_name = "hedron_compile_commands",
+    remote = "https://github.com/hedronvision/bazel-compile-commands-extractor.git",
+    commit = "0e990032f3c5a866e72615cf67e5ce22186dcb97",
+    # Replace the commit hash (above) with the latest (https://github.com/hedronvision/bazel-compile-commands-extractor/commits/main).
+    # Even better, set up Renovate and let it do the work for you (see "Suggestion: Updates" in the README).
+)
+
+# Use module extensions for LLVM and other dependencies that aren't in BCR
+mlir_tutorial_deps = use_extension("//:extensions.bzl", "mlir_tutorial_deps")
+use_repo(mlir_tutorial_deps, 
+    "llvm-raw", 
+    "llvm_zstd", 
+    "llvm_zlib"
+)
+
+# The subset of LLVM backend targets that should be compiled
+_LLVM_TARGETS = [
+    "X86",
+    # The bazel dependency graph for mlir-opt fails to load (at the analysis
+    # step) without the NVPTX target in this list, because mlir/test:TestGPU
+    # depends on the //llvm:NVPTXCodeGen target, which is not defined unless this
+    # is included. @j2kun asked the LLVM maintiners for tips on how to fix this,
+    # see https://github.com/llvm/llvm-project/issues/63135
+    "NVPTX",
+    # Needed for Apple M1 targets, see
+    # https://github.com/j2kun/mlir-tutorial/issues/11
+    "AArch64",
+]
+
+# Configure LLVM project using use_repo_rule
+llvm_configure = use_repo_rule("@llvm-raw//utils/bazel:configure.bzl", "llvm_configure")
+llvm_configure(
+    name = "llvm-project",
+    targets = _LLVM_TARGETS,
+)
+
+# Configure Python dependencies
+python = use_extension("@rules_python//python/extensions:python.bzl", "python")
+python.toolchain(python_version = "3.13")
+use_repo(python, "python_3_13")
+
+pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
+pip.parse(
+    hub_name = "mlir_tutorial_pip_deps",
+    python_version = "3.13",
+    requirements_lock = "//:requirements.txt",
+)
+use_repo(pip, "mlir_tutorial_pip_deps") 

README.md

@@ -30,6 +30,11 @@ the tutorial series and explained in the first article,
 The CMake build is maintained, but was added at article 10 (Dialect Conversion)
 and will not be explained in the articles.
 
+**Note**: This project has been upgraded to Bazel 8.3.1 and migrated to use 
+Bzlmod for dependency management, replacing the traditional WORKSPACE file 
+approach. Dependencies are now managed through `MODULE.bazel` using the 
+Bazel Central Registry (BCR) where possible.
+
 ### Prerequisites
 
 Install Bazelisk via instructions at
@@ -39,6 +44,9 @@ This should create the `bazel` command on your system.
 You should also have a modern C++ compiler on your system, either `gcc` or
 `clang`, which Bazel will detect.
 
+**Bazel Version**: This project requires Bazel 8.3.1 or newer. The specific
+version is pinned in `.bazelversion`.
+
 ### Build and test
 
 Run
@@ -48,6 +56,19 @@ bazel build ...:all
 bazel test ...:all
 ```
 
+### Dependency Management
+
+The project uses Bzlmod (MODULE.bazel) for dependency management:
+
+- **Core dependencies**: Managed through Bazel Central Registry (BCR)
+  - rules_python, rules_java, protobuf, abseil-cpp, or-tools, etc.
+- **LLVM dependencies**: Managed through custom module extension
+  - LLVM/MLIR source code via git repository
+- **Development tools**: hedron_compile_commands via git_override
+
+This approach provides better dependency resolution, versioning, and 
+compatibility compared to the legacy WORKSPACE approach.
+
 ## CMake build
 
 CMake is one of two supported build systems for this tutorial. The other is