Remove use of reverse iterators in repairIntervalsInRange(). While they were

arguably better than forward iterators for this use case, they are confusing and
there are some implementation problems with reverse iterators and MI bundles.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175393 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 13 insertions, 16 deletions

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index e09ac4bfbd..0978d7342e 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1035,19 +1035,24 @@ void LiveIntervals::handleMoveIntoBundle(MachineInstr* MI,
 
 void
 LiveIntervals::repairIntervalsInRange(MachineBasicBlock *MBB,
-                                     MachineBasicBlock::reverse_iterator RBegin,
-                                     MachineBasicBlock::reverse_iterator REnd,
+                                      MachineBasicBlock::iterator Begin,
+                                      MachineBasicBlock::iterator End,
                                       ArrayRef<unsigned> OrigRegs) {
+  SlotIndex startIdx;
+  if (Begin == MBB->begin())
+    startIdx = getMBBStartIdx(MBB);
+  else
+    startIdx = getInstructionIndex(prior(Begin)).getRegSlot();
+
   for (unsigned i = 0, e = OrigRegs.size(); i != e; ++i) {
     unsigned Reg = OrigRegs[i];
     if (!TargetRegisterInfo::isVirtualRegister(Reg))
       continue;
 
     LiveInterval &LI = getInterval(Reg);
-    SlotIndex startIdx = (REnd == MBB->rend()) ? getMBBStartIdx(MBB)
-                                               : getInstructionIndex(&*REnd);
-    for (MachineBasicBlock::reverse_iterator I = RBegin; I != REnd; ++I) {
-      MachineInstr *MI = &*I;
+    for (MachineBasicBlock::iterator I = End; I != Begin;) {
+      --I;
+      MachineInstr *MI = I;
       SlotIndex instrIdx = getInstructionIndex(MI);
 
       for (MachineInstr::mop_iterator OI = MI->operands_begin(),
@@ -1059,7 +1064,7 @@ LiveIntervals::repairIntervalsInRange(MachineBasicBlock *MBB,
         assert(MO.isUse() && "Register defs are not yet supported.");
 
         if (!LI.liveAt(instrIdx)) {
-          LiveRange *LR = LI.getLiveRangeContaining(startIdx.getRegSlot());
+          LiveRange *LR = LI.getLiveRangeContaining(startIdx);
           assert(LR && "Used registers must be live-in.");
           LR->end = instrIdx.getRegSlot();
           break;
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index f22a70716e..898e165fee 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -851,15 +851,7 @@ MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
 
     // Update all intervals for registers whose uses may have been modified by
     // updateTerminator().
-    iterator FirstTerminator = getFirstTerminator();
-    reverse_iterator PreTerminators;
-    if (FirstTerminator == begin())
-      PreTerminators = rend();
-    else if (FirstTerminator == end())
-      PreTerminators = rbegin();
-    else
-      PreTerminators = reverse_iterator(FirstTerminator);
-    LIS->repairIntervalsInRange(this, rbegin(), PreTerminators, UsedRegs);
+    LIS->repairIntervalsInRange(this, getFirstTerminator(), end(), UsedRegs);
   }
 
   if (MachineDominatorTree *MDT =