[NinoFloris]

Centralize exception and write-barrier proofs in value numbering so CSE and later phases can use them without rediscovering the same facts.

VN drops exception items already ruled out by dominating checks or fully covered joins, including exceptional entries. It publishes non-faulting and arithmetic properties during the numbering walk, and classifies write barriers after all reaching values have been numbered. This removes the duplicate VN-based non-null walk and write-barrier classification from global assertion propagation, and makes the information available earlier to RBO and hoisting.

CI results (negative is better):

Platform	TP	Code size	PerfScore (geomean)
Linux x64	−0.233%	−2,639 B	−0.013%
Windows x64	−0.119%	−58,988 B	−0.015%
Linux arm64	−0.164%	−239,088 B	−0.018%
Windows arm64	−0.181%	−248,680 B	−0.019%
macOS arm64	−0.163%	−14,744 B	+0.031%
Linux arm	−0.241%	−623,900 B	−0.012%
Windows x86	−0.323%	−1,014,945 B	−0.012%
Wasm	−0.289%	−2,455,267 B	−0.098%

The awkward part is preserving contextual proofs when code moves. GTF_ORDER_DOMINATED marks the operation whose safety depends on an earlier check. It is local to that operation and is not propagated to parent nodes or folded into GTF_ORDER_SIDEEFF. Tree transformations inspect operands when they need a subtree summary, while LIR checks the operations directly. Hoisting receives scoped block anchors to check that the required facts still hold at the destination.

Focused regression tests cover exceptional entry into a finally, conditional hoisting, and write-barrier classification without losing stores, faults or live references.

[azure-pipelines]

Azure Pipelines:
Successfully started running 5 pipeline(s).
10 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.