Move getBundleStart() into MachineInstrBundle.h.

This allows the function to be inlined, and makes it suitable for use in
getInstructionIndex().

Also provide a const version. C++ is great for touch typing practice.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151782 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 03ca72e..3e16efa 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1522,7 +1522,7 @@
   SlotIndex OldIndex = indexes_->getInstructionIndex(MI);
   indexes_->removeMachineInstrFromMaps(MI);
   SlotIndex NewIndex = MI->isInsideBundle() ?
-                        indexes_->getInstructionIndex(MI->getBundleStart()) :
+                        indexes_->getInstructionIndex(MI) :
                         indexes_->insertMachineInstrInMaps(MI);
   assert(getMBBStartIdx(MI->getParent()) <= OldIndex &&
          OldIndex < getMBBEndIdx(MI->getParent()) &&