JIT: Don't transform infinite loops in fgOptimizeBranchToEmptyUnconditional (#116822)

Fixes #116701.

Author: amanasifkhalid

src/coreclr/jit/fgopt.cpp

@@ -1298,6 +1298,17 @@ bool Compiler::fgOptimizeBranchToEmptyUnconditional(BasicBlock* block, BasicBloc
     assert(bDest->isEmpty());
     assert(bDest->KindIs(BBJ_ALWAYS));
 
+    BasicBlock* const bDestTarget = bDest->GetTarget();
+
+    // Don't redirect 'block' to 'bDestTarget' if the latter jumps to 'bDest'.
+    // This will lead the JIT to consider optimizing 'block' -> 'bDestTarget' -> 'bDest',
+    // entering an infinite loop.
+    //
+    if (bDestTarget->GetUniqueSucc() == bDest)
+    {
+        optimizeJump = false;
+    }
+
     // We do not optimize jumps between two different try regions.
     // However jumping to a block that is not in any try region is OK
     //
@@ -1307,7 +1318,7 @@ bool Compiler::fgOptimizeBranchToEmptyUnconditional(BasicBlock* block, BasicBloc
     }
 
     // Don't optimize a jump to a removed block
-    if (bDest->GetTarget()->HasFlag(BBF_REMOVED))
+    if (bDestTarget->HasFlag(BBF_REMOVED))
     {
         optimizeJump = false;
     }