增加 mxcc 编译超时控制

[ghangz]

该 PR 为 mxcc 编译流程增加超时控制，避免异常工具链或错误参数导致测试任务长期卡住。

这个修改面向沐曦 GPU 适配场景中比较容易影响开发、构建或验证稳定性的环节，把原来需要人工排查的问题前移到工具链、运行前检查或基准脚本中处理。实现上保持对现有默认行为的兼容，只在检测到明确配置、输入或环境异常时给出更直接的诊断，避免引入额外运行依赖，也方便维护者独立审阅该分支。

已在沐曦算力环境中完成对应分支验证，验证记录包含真实运行日志、命令输出和失败路径检查，本地归档目录为：E:/Documents/muxi/测试报告/mcTVM_new_toolchain_validation_20260608。提交分支：mengz/mxcc-compile-timeout，目标仓库：MetaX-MACA/mcTVM。

[gemini-code-assist]

Code Review

This pull request introduces a timeout mechanism for MACA compilation in TVM by reading the TVM_MXCC_TIMEOUT environment variable and applying it to the subprocess communication. It also adds corresponding unit tests. The reviewer feedback suggests wrapping proc.kill() in a try-except block to handle potential OSError exceptions during timeout handling, and simplifying the unit tests by directly importing the helper function instead of dynamically parsing and executing it with AST.

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[gemini-code-assist]

在捕获 subprocess.TimeoutExpired 异常后调用 proc.kill() 时，如果子进程在超时瞬间或之后刚好自行结束，可能会抛出 ProcessLookupError（或在 Windows 上抛出其他 OSError）。为了提高代码的健壮性，建议使用 try...except OSError: 块包裹 proc.kill()，以防止因竞态条件导致编译流程异常崩溃。

Suggested change

	except subprocess.TimeoutExpired as err:
	proc.kill()
	out, _ = proc.communicate()
	except subprocess.TimeoutExpired as err:
	try:
	proc.kill()
	except OSError:
	pass
	out, _ = proc.communicate()

[gemini-code-assist]

使用 ast.parse 和 exec 动态加载并执行 _get_mxcc_timeout 函数过于复杂且非常脆弱（例如，如果未来该函数依赖了其他未被提取的导入或辅助函数，测试将会失败）。

既然这是 TVM 的测试套件，可以直接从 tvm.contrib.mxcc 导入该函数进行测试。此外，使用 pytest.raises 来断言异常比手动 try-except-else 更符合 Python 测试的最佳实践。

Suggested change

	import ast
	import os
	from pathlib import Path
	from unittest.mock import patch
	def _load_timeout_helper():
	source_path = (
	Path(__file__).resolve().parents[3] / "python" / "tvm" / "contrib" / "mxcc.py"
	)
	tree = ast.parse(source_path.read_text(encoding="utf-8"))
	nodes = [
	node
	for node in tree.body
	if (
	isinstance(node, ast.Import)
	and all(alias.name == "os" for alias in node.names)
	)
	or (isinstance(node, ast.FunctionDef) and node.name == "_get_mxcc_timeout")
	]
	module = ast.Module(body=nodes, type_ignores=[])
	ast.fix_missing_locations(module)
	namespace = {}
	exec(compile(module, str(source_path), "exec"), namespace)
	return namespace["_get_mxcc_timeout"]
	def test_mxcc_timeout_accepts_positive_float():
	get_timeout = _load_timeout_helper()
	with patch.dict(os.environ, {"TVM_MXCC_TIMEOUT": "12.5"}, clear=True):
	assert get_timeout() == 12.5
	def test_mxcc_timeout_rejects_invalid_value():
	get_timeout = _load_timeout_helper()
	with patch.dict(os.environ, {"TVM_MXCC_TIMEOUT": "0"}, clear=True):
	try:
	get_timeout()
	except ValueError as err:
	assert "positive number" in str(err)
	else:
	raise AssertionError("expected ValueError")
	if __name__ == "__main__":
	test_mxcc_timeout_accepts_positive_float()
	test_mxcc_timeout_rejects_invalid_value()
	import os
	from unittest.mock import patch
	import pytest
	from tvm.contrib.mxcc import _get_mxcc_timeout
	def test_mxcc_timeout_accepts_positive_float():
	with patch.dict(os.environ, {"TVM_MXCC_TIMEOUT": "12.5"}, clear=True):
	assert _get_mxcc_timeout() == 12.5
	def test_mxcc_timeout_rejects_invalid_value():
	with patch.dict(os.environ, {"TVM_MXCC_TIMEOUT": "0"}, clear=True):
	with pytest.raises(ValueError, match="positive number"):
	_get_mxcc_timeout()
	if __name__ == "__main__":
	test_mxcc_timeout_accepts_positive_float()
	test_mxcc_timeout_rejects_invalid_value()