MachineInstrBundle: Pass iterators to getBundle(Start|End); NFC

This is a function to go backwards in a block to find the first
instruction in a bundle, so iterator is a more natural choice for
parameter/return rather than a reference to a MachineInstruction.

llvm-svn: 285051
diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index ba9bf90..b968260 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -1222,7 +1222,7 @@
   // might set it on too many operands.  We will clear as many flags as we
   // can though.
   MachineBasicBlock::instr_iterator Begin = MI->getIterator();
-  MachineBasicBlock::instr_iterator End = getBundleEnd(*MI);
+  MachineBasicBlock::instr_iterator End = getBundleEnd(Begin);
   while (Begin != End) {
     if (NewKillState) {
       if ((--End)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
@@ -1344,7 +1344,7 @@
         DEBUG({
           if (MI.getOpcode() == TargetOpcode::BUNDLE) {
             MachineBasicBlock::instr_iterator Begin = MI.getIterator();
-            MachineBasicBlock::instr_iterator End = getBundleEnd(MI);
+            MachineBasicBlock::instr_iterator End = getBundleEnd(Begin);
             while (++Begin != End)
               DEBUG(Begin->dump());
           }