[llvm] [RegisterCoalescer] Avoid retrying high-cost joins for live intervals (PR #207976)

[Mingjie Xu via llvm-commits]

================
@@ -2222,7 +2228,10 @@ bool RegisterCoalescer::joinCopy(
 
     // Otherwise, we are unable to join the intervals.
     LLVM_DEBUG(dbgs() << "\tInterference!\n");
----------------
Enna1 wrote:

Should we update this debug output?

https://github.com/llvm/llvm-project/pull/207976