Merge branch 'python-example' into 'main'

Add example checkscript in python

See merge request repositories/verilator-infrastructure-bugpoint!30

README.md

@@ -39,6 +39,7 @@ First, you need to prepare:
 - a script that takes the path to a SystemVerilog file as the first argument and asserts that the same bug (or another property you wish to preserve) is still occurring.
 It should exit with 0 if the assertion is successful.
 For reference, see [`examples/caliptra_verilation_err/sv-bugpoint-check.sh`](examples/caliptra_verilation_err/sv-bugpoint-check.sh) and [`examples/caliptra_vcd/sv-bugpoint-check.sh`](examples/caliptra_vcd/sv-bugpoint-check.sh).
+The script can be written in any language you are comfortable with, it just needs to be an executable. See the Python example: [`examples/caliptra_verilation_err/sv-bugpoint-check.py`](examples/caliptra_verilation_err/sv-bugpoint-check.py).
 - SystemVerilog code that `sv-bugpoint` will attempt to minimize. In order to get one from a multi-file design,
 you can use a preprocessor of your choice (e.g `verilator -E -P [other flags...] > sv-bugpoint-input.sv`).
 

examples/caliptra_verilation_err/sv-bugpoint-check.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+"""
+SPDX-License-Identifier: Apache-2.0
+
+test script that asserts that verilation fails with same error message as in golden file
+
+meant to debug case with caliptra-rtl@67fc658 and verilator@9a8e68928
+"""
+
+import subprocess
+import sys
+import shutil
+import shlex
+import os
+
+
+def verilate_and_save_errmsg(verilator_argv):
+    """run verilator, strip out volatile metadata from stderr and save it to file"""
+    subprocess.Popen(
+        ["sv-bugpoint-strip-verilator-errmsg"],
+        stdin=subprocess.Popen(verilator_argv, stderr=subprocess.PIPE).stderr,
+        stdout=open("actual_stderr", "w", encoding="utf-8"),
+    ).communicate()
+
+
+def check():
+    """check if actual equals golden, print diff if not"""
+    diff_proc = subprocess.run(
+        ["diff", "golden_stderr", "actual_stderr", "--color"], check=False
+    )
+    return diff_proc.returncode == 0
+
+
+CMD = """
+verilator --cc --autoflush --timescale 1ns/1ps --timing --top-module caliptra_top_tb \
+  -Wno-WIDTH -Wno-UNOPTFLAT -Wno-LITENDIAN -Wno-CMPCONST -Wno-MULTIDRIVEN -Wno-UNPACKED -Wno-ALWCOMBORDER
+"""
+
+verilate_and_save_errmsg(shlex.split(CMD) + [sys.argv[1]])
+print("\n\n\n", end="")
+if check():
+    print("SUCCESS\n\n\n", end="")
+    sys.exit(0)
+else:
+    if "GOLDEN" in os.environ:
+        shutil.copyfile("actual_stderr", "golden_stderr")
+    sys.exit(1)