add test with deep execution tree without stores.

[sandreenko]

It will not fail if the compiler spills trees from eeStack from time to time or all recursive walkers are replaced by non-recursive algorithms.

[JosephTremoulet]

LGTM, thanks for adding this.

[pgavlin]

Is there a reason the existing https://github.com/dotnet/coreclr/blob/master/tests/src/JIT/jit64/opt/cse/hugeexpr1.cs is insufficient for this scenario?

[sandreenko]

I didn't see any failures in ci when I disabled stack spilling and send PR.
I think hugeexpt1.cs doesn't have very deep tree, the biggest one has deep near 600 as I see.

[pgavlin]

Hm. I am pretty sure that we're already covering this somewhere... LGTM if we aren't, in any case.

[sandreenko]

I want to double check.

[sandreenko]

It is pretty interesting that we see this failure only in Windows_NT x64 Debug Build and Test. It is what I tested locally.

And as you see there are no failures on existing tests.
I think I should try to make it fails in Release and Checked. Maybe just to increase the depth of the tree.

[sandreenko]

Ok, now it looks fine. It breaks in all modes (x64/x86 Debug/Release/Checked).
So I want to merge it as soon as testing will be finished.