JIT: Use jitstd::utility::scoped_code to unmark trees during lowering

[amanasifkhalid]

Fixes #105971. Lowering::TryMakeIndirsAdjacent and Lowering::TryMakeIndirAndStoreAdjacent require that no GenTree nodes are marked upon entry, and that marked nodes are cleared upon exit, but in the case of the first method, not every exit path was unmarking the tree. jitstd::utility::scoped_code makes this invariant clear.

[amanasifkhalid]

/azp run runtime-coreclr superpmi-asmdiffs-checked-release

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[amanasifkhalid]

/azp run runtime-coreclr superpmi-asmdiffs-checked-release

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[amanasifkhalid]

cc @dotnet/jit-contrib, @jakobbotsch PTAL. Thanks!

[jakobbotsch]

Thanks for fixing this!

[teo-tsirpanis]

There's a chance (I'm not 100% sure, I haven't tried it) that C++ can deduce the template argument, which can enable inlining the auto code = variable.

[teo-tsirpanis]

Suggested change

	auto code = [this, indir] {
	UnmarkTree(indir);
	};
	jitstd::utility::scoped_code<decltype(code)> finally(code);
	jitstd::utility::scoped_code finally([this, indir] {
	UnmarkTree(indir);
	});

[teo-tsirpanis]

Suggested change

	auto code = [this, store] {
	UnmarkTree(store);
	};
	jitstd::utility::scoped_code<decltype(code)> finally(code);
	jitstd::utility::scoped_code finally([this, store] {
	UnmarkTree(store);
	});

[amanasifkhalid]

There's a chance (I'm not 100% sure, I haven't tried it) that C++ can deduce the template argument, which can enable inlining the auto code = variable.

Thank you for the suggestion! I tried this, and it didn't compile... I don't think this type deduction works when it's used on a templated class, at least in C++11.

[teo-tsirpanis]

Oh you are on C++11, this feature was added in C++17. 😔

[amanasifkhalid]

Oh you are on C++11, this feature was added in C++17. 😔

Yeah, I'm not sure if we have any plans to upgrade in the near future, though it's helpful to know this is another pattern we could clean up if we did upgrade.