Clarify what mysterious check means.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108005 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 5eb1a00..43ef9a1 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -300,6 +300,9 @@
       for (MachineBasicBlock::const_iterator
              II = MBB->begin(), IE = MBB->end(); II != IE; ++II) {
         const TargetInstrDesc &TID = TM.getInstrInfo()->get(II->getOpcode());
+
+        // Operand 1 of an inline asm instruction indicates whether the asm
+        // needs stack or not.
         if ((II->isInlineAsm() && II->getOperand(1).getImm()) ||
             (TID.isCall() && !TID.isReturn())) {
           MFI->setHasCalls(true);