[mlir][utils] Add script to verify canonicalizations against Alive2 (#91867)

This script takes IR before and after canonicalization, translates it
into llvm IR and converts it to format suitable for Alive2
https://alive2.llvm.org/ce/

This is primarily for arith canonicalizations verification, but
technically it can be adapted for any dialect translatable to llvm.

Usage `python verify_canon.py canonicalize.mlir -f func1 func2 ...`

Example output: https://alive2.llvm.org/ce/z/KhQs4J

Initial discussion:
#91646 (review)

Author: Hardcode84

mlir/utils/verify-canon/verify_canon.py

@@ -0,0 +1,77 @@
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+# This script is a helper to verify canonicalization patterns using Alive2
+# https://alive2.llvm.org/ce/.
+# It performs the following steps:
+# - Filters out the provided test functions.
+# - Runs the canonicalization pass on the remaining functions.
+# - Lowers both the original and the canonicalized functions to LLVM IR.
+# - Prints the canonicalized and the original functions side-by-side in a format
+#   that can be copied into Alive2 for verification.
+# Example: `python verify_canon.py canonicalize.mlir -f func1 func2 func3`
+
+import subprocess
+import tempfile
+import sys
+from pathlib import Path
+from argparse import ArgumentParser
+
+
+def filter_funcs(ir, funcs):
+    if not funcs:
+        return ir
+
+    funcs_str = ",".join(funcs)
+    return subprocess.check_output(
+        ["mlir-opt", f"--symbol-privatize=exclude={funcs_str}", "--symbol-dce"],
+        input=ir,
+    )
+
+
+def add_func_prefix(src, prefix):
+    return src.replace("@", "@" + prefix)
+
+
+def merge_ir(chunks):
+    files = []
+    for chunk in chunks:
+        tmp = tempfile.NamedTemporaryFile(suffix=".ll")
+        tmp.write(chunk)
+        tmp.flush()
+        files.append(tmp)
+
+    return subprocess.check_output(["llvm-link", "-S"] + [f.name for f in files])
+
+
+if __name__ == "__main__":
+    parser = ArgumentParser()
+    parser.add_argument("file")
+    parser.add_argument("-f", "--func-names", nargs="+", default=[])
+    args = parser.parse_args()
+
+    file = args.file
+    funcs = args.func_names
+
+    orig_ir = Path(file).read_bytes()
+    orig_ir = filter_funcs(orig_ir, funcs)
+
+    to_llvm_args = ["--convert-to-llvm"]
+    orig_args = ["mlir-opt"] + to_llvm_args
+    canon_args = ["mlir-opt", "-canonicalize"] + to_llvm_args
+    translate_args = ["mlir-translate", "-mlir-to-llvmir"]
+
+    orig = subprocess.check_output(orig_args, input=orig_ir)
+    canonicalized = subprocess.check_output(canon_args, input=orig_ir)
+
+    orig = subprocess.check_output(translate_args, input=orig)
+    canonicalized = subprocess.check_output(translate_args, input=canonicalized)
+
+    enc = "utf-8"
+    orig = bytes(add_func_prefix(orig.decode(enc), "src_"), enc)
+    canonicalized = bytes(add_func_prefix(canonicalized.decode(enc), "tgt_"), enc)
+
+    res = merge_ir([orig, canonicalized])
+
+    print(res.decode(enc))