[release/8.0] Fix fgOptimizeAddition opt for AOT #94418
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Backport of #94350 to release/8.0
/cc @EgorBo
Customer Impact
RyuJIT had an optimization that wasn't NativeAOT/R2R friendly:
(X + Const1) + (Y + Const2)
was transformed into(X + Y) + Const3
(whereConst3
isConst1 + Const2
)while in some cases it's not allowed to fold constants which require "relocs" (AOT). It seems that this transformation had this bug for several releases but only in .NET 8.0 we start to hit it because unrelated optimizations (like early expansion of fields) introduced more opportunities for it. A small repro is demonstrated in #94332
Testing
outerloop/NativeAOT testing, local tests
Risk
Low