CodeGen: Avoid dereferencing end() when unconstifying iterators

Rather than doing a funny dance that relies on dereferencing end() not
crashing, add some API to MachineInstrBundleIterator to get a non-const
version of the iterator.

llvm-svn: 278870

1 files changed, 4 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/MachineScheduler.cpp b/llvm/lib/CodeGen/MachineScheduler.cpp
index 01ef9d834b6..e91fa051f36 100644
--- a/llvm/lib/CodeGen/MachineScheduler.cpp
+++ b/llvm/lib/CodeGen/MachineScheduler.cpp
@@ -251,8 +251,8 @@ priorNonDebug(MachineBasicBlock::const_iterator I,
 static MachineBasicBlock::iterator
 priorNonDebug(MachineBasicBlock::iterator I,
               MachineBasicBlock::const_iterator Beg) {
-  return const_cast<MachineInstr*>(
-    &*priorNonDebug(MachineBasicBlock::const_iterator(I), Beg));
+  return priorNonDebug(MachineBasicBlock::const_iterator(I), Beg)
+      .getNonConstIterator();
 }
 
 /// If this iterator is a debug value, increment until reaching the End or a
@@ -271,12 +271,8 @@ nextIfDebug(MachineBasicBlock::const_iterator I,
 static MachineBasicBlock::iterator
 nextIfDebug(MachineBasicBlock::iterator I,
             MachineBasicBlock::const_iterator End) {
-  // Cast the return value to nonconst MachineInstr, then cast to an
-  // instr_iterator, which does not check for null, finally return a
-  // bundle_iterator.
-  return MachineBasicBlock::instr_iterator(
-    const_cast<MachineInstr*>(
-      &*nextIfDebug(MachineBasicBlock::const_iterator(I), End)));
+  return nextIfDebug(MachineBasicBlock::const_iterator(I), End)
+      .getNonConstIterator();
 }
 
 /// Instantiate a ScheduleDAGInstrs that will be owned by the caller.