gitlab: add a new build_unit job to track build size

We want to reduce the total number of build units in the system to get
on our way to a single binary. It will help to have some numbers so
lets add a job to gitlab to track our progress.

Cc: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Cc: Philippe Mathieu-Daudé <philmd@linaro.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250304222439.2035603-19-alex.bennee@linaro.org>

.gitlab-ci.d/check-units.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+#
+# check-units.py: check the number of compilation units and identify
+#                 those that are rebuilt multiple times
+#
+# Copyright (C) 2025 Linaro Ltd.
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+from os import access, R_OK, path
+from sys import argv, exit
+import json
+from collections import Counter
+
+
+def extract_build_units(cc_path):
+    """
+    Extract the build units and their counds from compile_commands.json file.
+
+    Returns:
+        Hash table of ["unit"] = count
+    """
+
+    j = json.load(open(cc_path, 'r'))
+    files = [f['file'] for f in j]
+    build_units = Counter(files)
+
+    return build_units
+
+
+def analyse_units(build_units):
+    """
+    Analyse the build units and report stats and the top 10 rebuilds
+    """
+
+    print(f"Total source files: {len(build_units.keys())}")
+    print(f"Total build units: {sum(units.values())}")
+
+    # Create a sorted list by number of rebuilds
+    sorted_build_units = sorted(build_units.items(),
+                                key=lambda item: item[1],
+                                reverse=True)
+
+    print("Most rebuilt units:")
+    for unit, count in sorted_build_units[:20]:
+        print(f"  {unit} built {count} times")
+
+    print("Least rebuilt units:")
+    for unit, count in sorted_build_units[-10:]:
+        print(f"  {unit} built {count} times")
+
+
+if __name__ == "__main__":
+    if len(argv) != 2:
+        script_name = path.basename(argv[0])
+        print(f"Usage: {script_name} <path_to_compile_commands.json>")
+        exit(1)
+
+    cc_path = argv[1]
+    if path.isfile(cc_path) and access(cc_path, R_OK):
+        units = extract_build_units(cc_path)
+        analyse_units(units)
+        exit(0)
+    else:
+        print(f"{cc_path} doesn't exist or isn't readable")
+        exit(1)

.gitlab-ci.d/static_checks.yml

@@ -70,3 +70,25 @@ check-rust-tools-nightly:
     expire_in: 2 days
     paths:
       - rust/target/doc
+
+check-build-units:
+  extends: .base_job_template
+  stage: build
+  image: $CI_REGISTRY_IMAGE/qemu/debian:$QEMU_CI_CONTAINER_TAG
+  needs:
+    job: amd64-debian-container
+  before_script:
+    - source scripts/ci/gitlab-ci-section
+    - section_start setup "Install Tools"
+    - apt install --assume-yes --no-install-recommends jq
+    - section_end setup
+  script:
+    - mkdir build
+    - cd build
+    - section_start configure "Running configure"
+    - ../configure
+    - cd ..
+    - section_end configure
+    - section_start analyse "Analyse"
+    - .gitlab-ci.d/check-units.py build/compile_commands.json
+    - section_end analyse