[TVMC] Add configuration tir.add_lower_pass to option --pass-config

[leeexyz]

Hi All,

Sometimes, we should manipulate the Passes order or add new Passes not only for Relay Pass but for TIR Pass. the This PR add the configuration tir.add_lower_pass to --pass-config. It supports two types of TIR Pass, one is the built-in pass in TVM and another one is the external customized pass that is loaded by importlib.

Some use cases.

~/project/apache/tvm$ python -m tvm.driver.tvmc compile --target "llvm"  \
                                                   --output resnet50-v2-7-tvm.tar resnet50.onnx \
                                                   --pass-config "tir.add_lower_pass=1,tir.transform.UnrollLoop,2,tir.transform.UnrollLoop" 
{'tir.add_lower_pass': [(1, PrimFuncPass(tir.UnrollLoop, opt_level=0)), (2, PrimFuncPass(tir.UnrollLoop, opt_level=0))]}

~/project/apache/tvm$ python -m tvm.driver.tvmc compile --target "llvm" \
                                                   --output resnet50-v2-7-tvm.tar resnet50.onnx \
                                                   --pass-config "tir.add_lower_pass=1,tir.transform.UnrollLoop,2,tir.transform.UnrollLoop" \
                                                   --pass-config "tir.add_lower_pass=1,tir.transform.UnrollLoop"
{'tir.add_lower_pass': [(1, PrimFuncPass(tir.UnrollLoop, opt_level=0)), (2, PrimFuncPass(tir.UnrollLoop, opt_level=0)), (1, PrimFuncPass(tir.UnrollLoop, opt_level=0))]}

[leandron]

Just one remark, and I think we're good to go with this PR.

[leeexyz]

@leandron Would you mind helping me review again? :)

[leeexyz]

cc @leandron @junrushao1994 @comaniac 😊

[leandron]

LGTM

[leandron]

Thanks @leeexyz, this is merged now.