JIT: Set PGO data inconsistent when flow disappears in cast expansion (#112147)

Cast expansion can expand into a `BBJ_THROW` block. If that happens and
that block has flow into it, the PGO data becomes inconsistent.

Author: jakobbotsch

src/coreclr/jit/helperexpansion.cpp

@@ -2729,6 +2729,14 @@ bool Compiler::fgLateCastExpansionForCall(BasicBlock** pBlock, Statement* stmt,
         }
     }
 
+    if (fallbackBb->KindIs(BBJ_THROW) && (fallbackBb->bbWeight != BB_ZERO_WEIGHT))
+    {
+        // This flow is disappearing.
+        JITDUMP("fgLateCastExpansionForCall: fallback " FMT_BB " throws and has flow into it. Data %s inconsistent.\n",
+                fallbackBb->bbNum, fgPgoConsistent ? "is now" : "was already");
+        fgPgoConsistent = false;
+    }
+
     // Bonus step: merge prevBb with nullcheckBb as they are likely to be mergeable
     if (fgCanCompactBlock(firstBb))
     {