[Keras][Bugfix] fix a bug about alpha attribute in LeakyReLU which lead to passes conflict

[jikechao]

The alpha attribute in LeakyReLU lacks exception checking. If the alpha=nan , the keras frontend can convert it to relay ir successful, but in the optimization stage, it will trigger an unexpected crash and throws TVMError: Observed 100 rewrite passes, possible conflicting passes?

The relay IR is the following:

This patch fixes the bug!

The StackTrace:

    model = relay.build_module.create_executor("graph", mod, tvm.cpu(0), 'llvm', params).evaluate()  # crash
  File "/workplace/software/tvm/tvm/python/tvm/relay/backend/interpreter.py", line 171, in evaluate
    return self._make_executor()
  File "/workplace/software/tvm/tvm/python/tvm/relay/build_module.py", line 519, in _make_executor
    mod = build(self.mod, target=self.target)
  File "/workplace/software/tvm/tvm/python/tvm/relay/build_module.py", line 372, in build
    mod_name=mod_name,
  File "/workplace/software/tvm/tvm/python/tvm/relay/build_module.py", line 169, in build
    mod_name,
  File "/workplace/software/tvm/tvm/python/tvm/_ffi/_ctypes/packed_func.py", line 237, in __call__
    raise get_last_ffi_error()
tvm._ffi.base.TVMError: Traceback (most recent call last):
  14: TVMFuncCall
  13: tvm::relay::backend::RelayBuildModule::GetFunction(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, tvm::runtime::ObjectPtr<tvm::runtime::Object> const&)::{lambda(tvm::runtime::TVMArgs, tvm::runtime::TVMRetValue*)#3}::operator()(tvm::runtime::TVMArgs, tvm::runtime::TVMRetValue*) const
  12: tvm::relay::backend::RelayBuildModule::Build(tvm::IRModule, tvm::runtime::Array<tvm::Target, void> const&, tvm::Target const&, tvm::relay::Executor const&, tvm::relay::Runtime const&, tvm::WorkspaceMemoryPools const&, tvm::ConstantMemoryPools const&, tvm::runtime::String)
  11: tvm::relay::backend::RelayBuildModule::BuildRelay(tvm::IRModule, tvm::runtime::String const&)
  10: tvm::relay::backend::RelayBuildModule::OptimizeImpl(tvm::IRModule)
  9: tvm::transform::Pass::operator()(tvm::IRModule) const
  8: tvm::transform::Pass::operator()(tvm::IRModule, tvm::transform::PassContext const&) const
  7: tvm::transform::SequentialNode::operator()(tvm::IRModule, tvm::transform::PassContext const&) const
  6: tvm::transform::Pass::operator()(tvm::IRModule, tvm::transform::PassContext const&) const
  5: tvm::relay::transform::FunctionPassNode::operator()(tvm::IRModule, tvm::transform::PassContext const&) const
  4: tvm::runtime::PackedFuncObj::Extractor<tvm::runtime::PackedFuncSubObj<tvm::runtime::TypedPackedFunc<tvm::relay::Function (tvm::relay::Function, tvm::IRModule, tvm::transform::PassContext)>::AssignTypedLambda<tvm::relay::transform::SimplifyExpr()::$_0>(tvm::relay::transform::SimplifyExpr()::$_0)::{lambda(tvm::runtime::TVMArgs const&, tvm::runtime::TVMRetValue*)#1}> >::Call(tvm::runtime::PackedFuncObj const*, tvm::runtime::TVMArgs, tvm::runtime::TVMRetValue*)
  3: tvm::relay::SimplifyExpr(tvm::RelayExpr const&, tvm::IRModule const&)
  2: tvm::relay::RewritePatterns(tvm::runtime::Array<tvm::relay::DFPatternCallback, void>, tvm::RelayExpr, tvm::IRModule)
  1: tvm::relay::PatternRewriter::Rewrite(tvm::runtime::Array<tvm::relay::DFPatternCallback, void> const&, tvm::RelayExpr const&)
  0: _ZN3tvm7runtime6detail
  File "/workplace/software/tvm/tvm/src/relay/ir/dataflow_matcher.cc", line 829
TVMError: Observed 100 rewrite passes, possible conflicting passes?

[tvm-bot]

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[jikechao]

@yongwww Could your willing to review this PR? Many thanks!

[Hzfengsy]

Please add a regression test for it.

[AndrewZhaoLuo]

I think it looks fine. Thanks for fixing this.

Please add a comment to indicate to people why things are gated on version revision.

[echuraev]

LGTM. Thank you for this PR and fixing this issue.

[echuraev]

@tvm-bot rerun

[echuraev]

@tvm-bot rerun

[echuraev]

@tvm-bot rerun

[echuraev]

@tvm-bot rerun