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/azp run runtime-coreclr pgo, runtime-coreclr libraries-pgo, runtime-coreclr pgostress

@jakobbotsch @dotnet/jit-contrib PTAL.Diffs. There are few things in the diffs:

1. Improvements where we were able to hoist/CSE casts.

2. Improvements where we realized block is cold and it doesn't need cast expansion, E.g.
   
   (it was previously expanded)

3. Regressions due to extra nullcheck this phase emits and no other phase can clean it up. But I already have a follow up patch to fix it via assertionprop

4. Possible regressions because of CSE'd class handle argument - I wasn't able to find them but it may happen. This phase works as is if I move it after assertionprop so I can rely on VN to get it. Probably will do that separately.

Will move more casts to this phase from importer (all of them hopefully). For now only recently introduced profiled casts are handled.

/azp run runtime-coreclr pgo, runtime-coreclr libraries-pgo

LGTM, but looks like CI is a bit unhappy.

Ah, I broke the control flow a bit - nullcheckBb used to jump straight to the use block without assigningtmp's value (but in most cases it was zeroed anyway so CImostly passed.

Instead, I now do:

Case 1:

tmp=obj;if (tmp!=null){if (tmp.pMT!=likelyClass)tmp=helperCallelseno-op;// this block will be collected}use(tmp);

Case 2 (likelyClass is known to never pass the type check):

tmp=obj;if (tmp!=null){if (tmp.pMT!=likelyClass)tmp=helperCallelsetmp=null;}use(tmp);

I can avoid the initialtmp = obj; by introducing an extra BB but I think this shape is simpler.

Failure is#97103