Enable the new LoopInfo algorithm by default.

The primary advantage is that loop optimizations will be applied in a
stable order. This helps debugging and unit test creation. It is also
a better overall implementation without pathologically bad performance
on deep functions.

On large functions (llvm-stress --size=200000 | opt -loops)
Before: 0.1263s
After:  0.0225s

On deep functions (after tweaking llvm-stress, thanks Nadav):
Before: 0.2281s
After:  0.0227s

See r158790 for more comments.

The loop tree is now consistently generated in forward order, but loop
passes are applied in reverse order over the program. If we have a
loop optimization that prefers forward order, that can easily be
achieved by adding a different type of LoopPassManager.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159183 91177308-0d34-0410-b5e6-96231b3b80d8

10 files changed, 52 insertions, 244 deletions

diff --git a/include/llvm/Analysis/LoopInfo.h b/include/llvm/Analysis/LoopInfo.h
index 14d87e0034..eeb482d82a 100644
--- a/include/llvm/Analysis/LoopInfo.h
+++ b/include/llvm/Analysis/LoopInfo.h
@@ -127,8 +127,12 @@ public:
   const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
   std::vector<LoopT *> &getSubLoopsVector() { return SubLoops; }
   typedef typename std::vector<LoopT *>::const_iterator iterator;
+  typedef typename std::vector<LoopT *>::const_reverse_iterator
+    reverse_iterator;
   iterator begin() const { return SubLoops.begin(); }
   iterator end() const { return SubLoops.end(); }
+  reverse_iterator rbegin() const { return SubLoops.rbegin(); }
+  reverse_iterator rend() const { return SubLoops.rend(); }
   bool empty() const { return SubLoops.empty(); }
 
   /// getBlocks - Get a list of the basic blocks which make up this loop.
@@ -431,8 +435,12 @@ public:
   /// function.
   ///
   typedef typename std::vector<LoopT *>::const_iterator iterator;
+  typedef typename std::vector<LoopT *>::const_reverse_iterator
+    reverse_iterator;
   iterator begin() const { return TopLevelLoops.begin(); }
   iterator end() const { return TopLevelLoops.end(); }
+  reverse_iterator rbegin() const { return TopLevelLoops.rbegin(); }
+  reverse_iterator rend() const { return TopLevelLoops.rend(); }
   bool empty() const { return TopLevelLoops.empty(); }
 
   /// getLoopFor - Return the inner most loop that BB lives in.  If a basic
@@ -525,19 +533,6 @@ public:
     return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
   }
 
-  void Calculate(DominatorTreeBase<BlockT> &DT);
-
-  LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT);
-
-  /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
-  /// of the NewParent Loop, instead of being a sibling of it.
-  void MoveSiblingLoopInto(LoopT *NewChild, LoopT *NewParent);
-
-  /// InsertLoopInto - This inserts loop L into the specified parent loop.  If
-  /// the parent loop contains a loop which should contain L, the loop gets
-  /// inserted into L instead.
-  void InsertLoopInto(LoopT *L, LoopT *Parent);
-
   /// Create the loop forest using a stable algorithm.
   void Analyze(DominatorTreeBase<BlockT> &DomTree);
 
@@ -570,8 +565,11 @@ public:
   /// function.
   ///
   typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
+  typedef LoopInfoBase<BasicBlock, Loop>::reverse_iterator reverse_iterator;
   inline iterator begin() const { return LI.begin(); }
   inline iterator end() const { return LI.end(); }
+  inline reverse_iterator rbegin() const { return LI.rbegin(); }
+  inline reverse_iterator rend() const { return LI.rend(); }
   bool empty() const { return LI.empty(); }
 
   /// getLoopFor - Return the inner most loop that BB lives in.  If a basic
diff --git a/include/llvm/Analysis/LoopInfoImpl.h b/include/llvm/Analysis/LoopInfoImpl.h
index 1be717cb71..c07fbf7aa8 100644
--- a/include/llvm/Analysis/LoopInfoImpl.h
+++ b/include/llvm/Analysis/LoopInfoImpl.h
@@ -354,185 +354,6 @@ void LoopBase<BlockT, LoopT>::print(raw_ostream &OS, unsigned Depth) const {
 }
 
 //===----------------------------------------------------------------------===//
-/// LoopInfo - This class builds and contains all of the top level loop
-/// structures in the specified function.
-///
-
-template<class BlockT, class LoopT>
-void LoopInfoBase<BlockT, LoopT>::Calculate(DominatorTreeBase<BlockT> &DT) {
-  BlockT *RootNode = DT.getRootNode()->getBlock();
-
-  for (df_iterator<BlockT*> NI = df_begin(RootNode),
-         NE = df_end(RootNode); NI != NE; ++NI)
-    if (LoopT *L = ConsiderForLoop(*NI, DT))
-      TopLevelLoops.push_back(L);
-}
-
-template<class BlockT, class LoopT>
-LoopT *LoopInfoBase<BlockT, LoopT>::
-ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
-  if (BBMap.count(BB)) return 0; // Haven't processed this node?
-
-  std::vector<BlockT *> TodoStack;
-
-  // Scan the predecessors of BB, checking to see if BB dominates any of
-  // them.  This identifies backedges which target this node...
-  typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
-  for (typename InvBlockTraits::ChildIteratorType I =
-         InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
-       I != E; ++I) {
-    typename InvBlockTraits::NodeType *N = *I;
-    // If BB dominates its predecessor...
-    if (DT.dominates(BB, N) && DT.isReachableFromEntry(N))
-      TodoStack.push_back(N);
-  }
-
-  if (TodoStack.empty()) return 0;  // No backedges to this block...
-
-  // Create a new loop to represent this basic block...
-  LoopT *L = new LoopT(BB);
-  BBMap[BB] = L;
-
-  while (!TodoStack.empty()) {  // Process all the nodes in the loop
-    BlockT *X = TodoStack.back();
-    TodoStack.pop_back();
-
-    if (!L->contains(X) &&         // As of yet unprocessed??
-        DT.isReachableFromEntry(X)) {
-      // Check to see if this block already belongs to a loop.  If this occurs
-      // then we have a case where a loop that is supposed to be a child of
-      // the current loop was processed before the current loop.  When this
-      // occurs, this child loop gets added to a part of the current loop,
-      // making it a sibling to the current loop.  We have to reparent this
-      // loop.
-      if (LoopT *SubLoop =
-          const_cast<LoopT *>(getLoopFor(X)))
-        if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
-          // Remove the subloop from its current parent...
-          assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
-          LoopT *SLP = SubLoop->ParentLoop;  // SubLoopParent
-          typename std::vector<LoopT *>::iterator I =
-            std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
-          assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?");
-          SLP->SubLoops.erase(I);   // Remove from parent...
-
-          // Add the subloop to THIS loop...
-          SubLoop->ParentLoop = L;
-          L->SubLoops.push_back(SubLoop);
-        }
-
-      // Normal case, add the block to our loop...
-      L->Blocks.push_back(X);
-
-      typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
-
-      // Add all of the predecessors of X to the end of the work stack...
-      TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
-                       InvBlockTraits::child_end(X));
-    }
-  }
-
-  // If there are any loops nested within this loop, create them now!
-  for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
-         E = L->Blocks.end(); I != E; ++I)
-    if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
-      L->SubLoops.push_back(NewLoop);
-      NewLoop->ParentLoop = L;
-    }
-
-  // Add the basic blocks that comprise this loop to the BBMap so that this
-  // loop can be found for them.
-  //
-  for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
-         E = L->Blocks.end(); I != E; ++I)
-    BBMap.insert(std::make_pair(*I, L));
-
-  // Now that we have a list of all of the child loops of this loop, check to
-  // see if any of them should actually be nested inside of each other.  We
-  // can accidentally pull loops our of their parents, so we must make sure to
-  // organize the loop nests correctly now.
-  {
-    std::map<BlockT *, LoopT *> ContainingLoops;
-    for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
-      LoopT *Child = L->SubLoops[i];
-      assert(Child->getParentLoop() == L && "Not proper child loop?");
-
-      if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
-        // If there is already a loop which contains this loop, move this loop
-        // into the containing loop.
-        MoveSiblingLoopInto(Child, ContainingLoop);
-        --i;  // The loop got removed from the SubLoops list.
-      } else {
-        // This is currently considered to be a top-level loop.  Check to see
-        // if any of the contained blocks are loop headers for subloops we
-        // have already processed.
-        for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
-          LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
-          if (BlockLoop == 0) {   // Child block not processed yet...
-            BlockLoop = Child;
-          } else if (BlockLoop != Child) {
-            LoopT *SubLoop = BlockLoop;
-            // Reparent all of the blocks which used to belong to BlockLoops
-            for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
-              ContainingLoops[SubLoop->Blocks[j]] = Child;
-
-            // There is already a loop which contains this block, that means
-            // that we should reparent the loop which the block is currently
-            // considered to belong to to be a child of this loop.
-            MoveSiblingLoopInto(SubLoop, Child);
-            --i;  // We just shrunk the SubLoops list.
-          }
-        }
-      }
-    }
-  }
-
-  return L;
-}
-
-/// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
-/// of the NewParent Loop, instead of being a sibling of it.
-template<class BlockT, class LoopT>
-void LoopInfoBase<BlockT, LoopT>::
-MoveSiblingLoopInto(LoopT *NewChild, LoopT *NewParent) {
-  LoopT *OldParent = NewChild->getParentLoop();
-  assert(OldParent && OldParent == NewParent->getParentLoop() &&
-         NewChild != NewParent && "Not sibling loops!");
-
-  // Remove NewChild from being a child of OldParent
-  typename std::vector<LoopT *>::iterator I =
-    std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
-              NewChild);
-  assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
-  OldParent->SubLoops.erase(I);   // Remove from parent's subloops list
-  NewChild->ParentLoop = 0;
-
-  InsertLoopInto(NewChild, NewParent);
-}
-
-/// InsertLoopInto - This inserts loop L into the specified parent loop.  If
-/// the parent loop contains a loop which should contain L, the loop gets
-/// inserted into L instead.
-template<class BlockT, class LoopT>
-void LoopInfoBase<BlockT, LoopT>::InsertLoopInto(LoopT *L, LoopT *Parent) {
-  BlockT *LHeader = L->getHeader();
-  assert(Parent->contains(LHeader) &&
-         "This loop should not be inserted here!");
-
-  // Check to see if it belongs in a child loop...
-  for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
-       i != e; ++i)
-    if (Parent->SubLoops[i]->contains(LHeader)) {
-      InsertLoopInto(L, Parent->SubLoops[i]);
-      return;
-    }
-
-  // If not, insert it here!
-  Parent->SubLoops.push_back(L);
-  L->ParentLoop = Parent;
-}
-
-//===----------------------------------------------------------------------===//
 /// Stable LoopInfo Analysis - Build a loop tree using stable iterators so the
 /// result does / not depend on use list (block predecessor) order.
 ///
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp
index c5e5bbe266..20c33a3d9d 100644
--- a/lib/Analysis/LoopInfo.cpp
+++ b/lib/Analysis/LoopInfo.cpp
@@ -44,10 +44,6 @@ static cl::opt<bool,true>
 VerifyLoopInfoX("verify-loop-info", cl::location(VerifyLoopInfo),
                 cl::desc("Verify loop info (time consuming)"));
 
-static cl::opt<bool>
-StableLoopInfo("stable-loops", cl::Hidden, cl::init(false),
-               cl::desc("Compute a stable loop tree."));
-
 char LoopInfo::ID = 0;
 INITIALIZE_PASS_BEGIN(LoopInfo, "loops", "Natural Loop Information", true, true)
 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
@@ -516,10 +512,7 @@ Loop *UnloopUpdater::getNearestLoop(BasicBlock *BB, Loop *BBLoop) {
 //
 bool LoopInfo::runOnFunction(Function &) {
   releaseMemory();
-  if (StableLoopInfo)
-    LI.Analyze(getAnalysis<DominatorTree>().getBase());
-  else
-    LI.Calculate(getAnalysis<DominatorTree>().getBase());    // Update
+  LI.Analyze(getAnalysis<DominatorTree>().getBase());
   return false;
 }
 
diff --git a/lib/Analysis/LoopPass.cpp b/lib/Analysis/LoopPass.cpp
index aba700ac5c..1540112fe1 100644
--- a/lib/Analysis/LoopPass.cpp
+++ b/lib/Analysis/LoopPass.cpp
@@ -162,7 +162,7 @@ void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
 // Recurse through all subloops and all loops  into LQ.
 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
   LQ.push_back(L);
-  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
+  for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I)
     addLoopIntoQueue(*I, LQ);
 }
 
@@ -183,8 +183,12 @@ bool LPPassManager::runOnFunction(Function &F) {
   // Collect inherited analysis from Module level pass manager.
   populateInheritedAnalysis(TPM->activeStack);
 
-  // Populate Loop Queue
-  for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
+  // Populate the loop queue in reverse program order. There is no clear need to
+  // process sibling loops in either forward or reverse order. There may be some
+  // advantage in deleting uses in a later loop before optimizing the
+  // definitions in an earlier loop. If we find a clear reason to process in
+  // forward order, then a forward variant of LoopPassManager should be created.
+  for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I)
     addLoopIntoQueue(*I, LQ);
 
   if (LQ.empty()) // No loops, skip calling finalizers
diff --git a/lib/CodeGen/MachineLoopInfo.cpp b/lib/CodeGen/MachineLoopInfo.cpp
index b7298e48ee..9f3829e3c0 100644
--- a/lib/CodeGen/MachineLoopInfo.cpp
+++ b/lib/CodeGen/MachineLoopInfo.cpp
@@ -18,7 +18,6 @@
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/Analysis/LoopInfoImpl.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;
 
@@ -26,10 +25,6 @@ using namespace llvm;
 template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
 template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
 
-static cl::opt<bool>
-StableLoopInfo("stable-machine-loops", cl::Hidden, cl::init(false),
-               cl::desc("Compute a stable loop tree."));
-
 char MachineLoopInfo::ID = 0;
 INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
                 "Machine Natural Loop Construction", true, true)
@@ -41,10 +36,7 @@ char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
 
 bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
   releaseMemory();
-  if (StableLoopInfo)
-    LI.Analyze(getAnalysis<MachineDominatorTree>().getBase());
-  else
-    LI.Calculate(getAnalysis<MachineDominatorTree>().getBase());    // Update
+  LI.Analyze(getAnalysis<MachineDominatorTree>().getBase());
   return false;
 }
 
diff --git a/test/CodeGen/X86/multiple-loop-post-inc.ll b/test/CodeGen/X86/multiple-loop-post-inc.ll
index 7491190b01..9f7d036cf1 100644
--- a/test/CodeGen/X86/multiple-loop-post-inc.ll
+++ b/test/CodeGen/X86/multiple-loop-post-inc.ll
@@ -1,9 +1,9 @@
 ; RUN: llc -asm-verbose=false -disable-branch-fold -disable-code-place -disable-tail-duplicate -march=x86-64 -mcpu=nehalem < %s | FileCheck %s
 ; rdar://7236213
-
-; Xfailed now that scheduler 2-address hack is disabled a lea is generated.
-; The code isn't any worse though.
-; XFAIL: *
+;
+; The scheduler's 2-address hack has been disabled, so there is
+; currently no good guarantee that this test will pass until the
+; machine scheduler develops an equivalent heuristic.
 
 ; CodeGen shouldn't require any lea instructions inside the marked loop.
 ; It should properly set up post-increment uses and do coalescing for
diff --git a/test/Transforms/LCSSA/unused-phis.ll b/test/Transforms/LCSSA/unused-phis.ll
index aa2ab96341..01b214b8e3 100644
--- a/test/Transforms/LCSSA/unused-phis.ll
+++ b/test/Transforms/LCSSA/unused-phis.ll
@@ -2,9 +2,9 @@
 ; CHECK: exit1:
 ; CHECK: .lcssa =
 ; CHECK: exit2:
-; CHECK: .lcssa2 =
+; CHECK: .lcssa1 =
 ; CHECK: exit3:
-; CHECK-NOT: .lcssa1 =
+; CHECK-NOT: .lcssa
 
 ; Test to ensure that when there are multiple exit blocks, PHI nodes are
 ; only inserted by LCSSA when there is a use dominated by a given exit
diff --git a/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll b/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
index 8389fe4643..c1fd588106 100644
--- a/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
+++ b/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
@@ -35,11 +35,11 @@
 ; CHECK:      loop_begin.us1:                                   ; preds = %loop_begin.backedge.us5, %.split.split.us
 ; CHECK-NEXT:   %var_val.us2 = load i32* %var
 ; CHECK-NEXT:   switch i32 2, label %default.us-lcssa.us-lcssa.us [
-; CHECK-NEXT:     i32 1, label %inc.us3
-; CHECK-NEXT:     i32 2, label %dec.us4
+; CHECK-NEXT:     i32 1, label %inc.us4
+; CHECK-NEXT:     i32 2, label %dec.us3
 ; CHECK-NEXT:   ]
 
-; CHECK:      dec.us4:                                          ; preds = %loop_begin.us1
+; CHECK:      dec.us3:                                          ; preds = %loop_begin.us1
 ; CHECK-NEXT:   call void @decf() noreturn nounwind
 ; CHECK-NEXT:   br label %loop_begin.backedge.us5
 
@@ -81,7 +81,7 @@ inc:
 dec:
   call void @decf() noreturn nounwind
   br label %loop_begin
-default:  
+default:
   br label %loop_exit
 loop_exit:
   ret i32 0
diff --git a/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll b/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
index 05d98d513e..f3db471199 100644
--- a/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
+++ b/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
@@ -19,15 +19,15 @@
 ; CHECK:        switch i32 1, label %second_switch.us [
 ; CHECK-NEXT:     i32 1, label %inc.us
 
-; CHECK:      inc.us:                                           ; preds = %second_switch.us, %loop_begin.us
-; CHECK-NEXT:   call void @incf() noreturn nounwind
-; CHECK-NEXT:   br label %loop_begin.backedge.us
-
 ; CHECK:      second_switch.us:                                 ; preds = %loop_begin.us
 ; CHECK-NEXT:   switch i32 %d, label %default.us [
 ; CHECK-NEXT:     i32 1, label %inc.us
 ; CHECK-NEXT:   ]
 
+; CHECK:      inc.us:                                           ; preds = %second_switch.us, %loop_begin.us
+; CHECK-NEXT:   call void @incf() noreturn nounwind
+; CHECK-NEXT:   br label %loop_begin.backedge.us
+
 ; CHECK:      .split:                                           ; preds = %..split_crit_edge
 ; CHECK-NEXT:   br label %loop_begin
 
@@ -73,7 +73,7 @@ inc:
   call void @incf() noreturn nounwind
   br label %loop_begin
 
-default:  
+default:
   br label %loop_begin
 
 loop_exit:
diff --git a/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll b/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
index 1b186d6bec..270899642f 100644
--- a/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
+++ b/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
@@ -25,14 +25,14 @@
 ; CHECK-NEXT:   switch i32 1, label %second_switch.us.us [
 ; CHECK-NEXT:     i32 1, label %inc.us.us
 
-; CHECK:      inc.us.us:                                        ; preds = %second_switch.us.us, %loop_begin.us.us
-; CHECK-NEXT:   call void @incf() noreturn nounwind
-; CHECK-NEXT:   br label %loop_begin.backedge.us.us
-
 ; CHECK:      second_switch.us.us:                              ; preds = %loop_begin.us.us
 ; CHECK-NEXT:   switch i32 1, label %default.us.us [
 ; CHECK-NEXT:     i32 1, label %inc.us.us
 
+; CHECK:      inc.us.us:                                        ; preds = %second_switch.us.us, %loop_begin.us.us
+; CHECK-NEXT:   call void @incf() noreturn nounwind
+; CHECK-NEXT:   br label %loop_begin.backedge.us.us
+
 ; CHECK:      .split.us.split:                                  ; preds = %.split.us..split.us.split_crit_edge
 ; CHECK-NEXT:   br label %loop_begin.us
 
@@ -41,10 +41,6 @@
 ; CHECK-NEXT:   switch i32 1, label %second_switch.us [
 ; CHECK-NEXT:     i32 1, label %inc.us
 
-; CHECK:      inc.us:                                           ; preds = %second_switch.us.inc.us_crit_edge, %loop_begin.us
-; CHECK-NEXT:   call void @incf() noreturn nounwind
-; CHECK-NEXT:   br label %loop_begin.backedge.us
-
 ; CHECK:      second_switch.us:                                 ; preds = %loop_begin.us
 ; CHECK-NEXT:   switch i32 %d, label %default.us [
 ; CHECK-NEXT:     i32 1, label %second_switch.us.inc.us_crit_edge
@@ -53,6 +49,10 @@
 ; CHECK:      second_switch.us.inc.us_crit_edge:                ; preds = %second_switch.us
 ; CHECK-NEXT:   br i1 true, label %us-unreachable8, label %inc.us
 
+; CHECK:      inc.us:                                           ; preds = %second_switch.us.inc.us_crit_edge, %loop_begin.us
+; CHECK-NEXT:   call void @incf() noreturn nounwind
+; CHECK-NEXT:   br label %loop_begin.backedge.us
+
 ; CHECK:      .split:                                           ; preds = %..split_crit_edge
 ; CHECK-NEXT:   %3 = icmp eq i32 %d, 1
 ; CHECK-NEXT:   br i1 %3, label %.split.split.us, label %.split..split.split_crit_edge
@@ -65,21 +65,21 @@
 
 ; CHECK:      loop_begin.us1:                                   ; preds = %loop_begin.backedge.us6, %.split.split.us
 ; CHECK-NEXT:   %var_val.us2 = load i32* %var
-; CHECK-NEXT:   switch i32 %c, label %second_switch.us4 [
+; CHECK-NEXT:   switch i32 %c, label %second_switch.us3 [
 ; CHECK-NEXT:     i32 1, label %loop_begin.inc_crit_edge.us
 ; CHECK-NEXT:   ]
 
-; CHECK:      inc.us3:                                          ; preds = %loop_begin.inc_crit_edge.us, %second_switch.us4
-; CHECK-NEXT:   call void @incf() noreturn nounwind
-; CHECK-NEXT:   br label %loop_begin.backedge.us6
-
-; CHECK:      second_switch.us4:                                ; preds = %loop_begin.us1
+; CHECK:      second_switch.us3:                                ; preds = %loop_begin.us1
 ; CHECK-NEXT:   switch i32 1, label %default.us5 [
-; CHECK-NEXT:     i32 1, label %inc.us3
+; CHECK-NEXT:     i32 1, label %inc.us4
 ; CHECK-NEXT:   ]
 
+; CHECK:      inc.us4:                                          ; preds = %loop_begin.inc_crit_edge.us, %second_switch.us3
+; CHECK-NEXT:   call void @incf() noreturn nounwind
+; CHECK-NEXT:   br label %loop_begin.backedge.us6
+
 ; CHECK:      loop_begin.inc_crit_edge.us:                      ; preds = %loop_begin.us1
-; CHECK-NEXT:   br i1 true, label %us-unreachable.us-lcssa.us, label %inc.us3
+; CHECK-NEXT:   br i1 true, label %us-unreachable.us-lcssa.us, label %inc.us4
 
 ; CHECK:      .split.split:                                     ; preds = %.split..split.split_crit_edge
 ; CHECK-NEXT:   br label %loop_begin
@@ -127,7 +127,7 @@ inc:
   call void @incf() noreturn nounwind
   br label %loop_begin
 
-default:  
+default:
   br label %loop_begin
 
 loop_exit: