[llvm] [MIRPrinter] Don't print line break when there is no instructions (PR #80147)

[Quentin Dian via llvm-commits]

================
@@ -728,7 +728,7 @@ void MIPrinter::print(const MachineBasicBlock &MBB) {
     HasLineAttributes = true;
   }
 
-  if (HasLineAttributes)
+  if (HasLineAttributes && !MBB.instrs().empty())
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DianQK wrote:

> Makes sense to me: you only need the blank line separator if there are some successors/liveins _and_ some instructions.

`HasLineAttributes` should already contain successors and liveins.

https://github.com/llvm/llvm-project/pull/80147