Index: lib/Transforms/Scalar/LoopInterchange.cpp
===================================================================
--- lib/Transforms/Scalar/LoopInterchange.cpp
+++ lib/Transforms/Scalar/LoopInterchange.cpp
@@ -111,62 +111,59 @@
       Instruction *Dst = cast<Instruction>(*J);
       if (Src == Dst)
         continue;
+      // Ignore Input dependencies.
       if (isa<LoadInst>(Src) && isa<LoadInst>(Dst))
         continue;
+      // Track Output, Flow, and Anti dependencies.
       if (auto D = DI->depends(Src, Dst, true)) {
-        DEBUG(dbgs() << "Found Dependency between Src and Dst\n"
+        assert(D->isOrdered() && "Expected an output, flow or anti dep.");
+        DEBUG(StringRef DepType =
+                  D->isFlow() ? "flow" : D->isAnti() ? "anti" : "output";
+              dbgs() << "Found " << DepType
+                     << " dependency between Src and Dst\n"
                      << " Src:" << *Src << "\n Dst:" << *Dst << '\n');
-        if (D->isFlow()) {
-          // TODO: Handle Flow dependence.Check if it is sufficient to populate
-          // the Dependence Matrix with the direction reversed.
-          DEBUG(dbgs() << "Flow dependence not handled\n");
-          return false;
-        }
-        if (D->isAnti()) {
-          DEBUG(dbgs() << "Found Anti dependence\n");
-          unsigned Levels = D->getLevels();
-          char Direction;
-          for (unsigned II = 1; II <= Levels; ++II) {
-            const SCEV *Distance = D->getDistance(II);
-            const SCEVConstant *SCEVConst =
-                dyn_cast_or_null<SCEVConstant>(Distance);
-            if (SCEVConst) {
-              const ConstantInt *CI = SCEVConst->getValue();
-              if (CI->isNegative())
-                Direction = '<';
-              else if (CI->isZero())
-                Direction = '=';
-              else
-                Direction = '>';
-              Dep.push_back(Direction);
-            } else if (D->isScalar(II)) {
-              Direction = 'S';
-              Dep.push_back(Direction);
-            } else {
-              unsigned Dir = D->getDirection(II);
-              if (Dir == Dependence::DVEntry::LT ||
-                  Dir == Dependence::DVEntry::LE)
-                Direction = '<';
-              else if (Dir == Dependence::DVEntry::GT ||
-                       Dir == Dependence::DVEntry::GE)
-                Direction = '>';
-              else if (Dir == Dependence::DVEntry::EQ)
-                Direction = '=';
-              else
-                Direction = '*';
-              Dep.push_back(Direction);
-            }
-          }
-          while (Dep.size() != Level) {
-            Dep.push_back('I');
+        unsigned Levels = D->getLevels();
+        char Direction;
+        for (unsigned II = 1; II <= Levels; ++II) {
+          const SCEV *Distance = D->getDistance(II);
+          const SCEVConstant *SCEVConst =
+              dyn_cast_or_null<SCEVConstant>(Distance);
+          if (SCEVConst) {
+            const ConstantInt *CI = SCEVConst->getValue();
+            if (CI->isNegative())
+              Direction = '<';
+            else if (CI->isZero())
+              Direction = '=';
+            else
+              Direction = '>';
+            Dep.push_back(Direction);
+          } else if (D->isScalar(II)) {
+            Direction = 'S';
+            Dep.push_back(Direction);
+          } else {
+            unsigned Dir = D->getDirection(II);
+            if (Dir == Dependence::DVEntry::LT ||
+                Dir == Dependence::DVEntry::LE)
+              Direction = '<';
+            else if (Dir == Dependence::DVEntry::GT ||
+                     Dir == Dependence::DVEntry::GE)
+              Direction = '>';
+            else if (Dir == Dependence::DVEntry::EQ)
+              Direction = '=';
+            else
+              Direction = '*';
+            Dep.push_back(Direction);
           }
+        }
+        while (Dep.size() != Level) {
+          Dep.push_back('I');
+        }
 
-          DepMatrix.push_back(Dep);
-          if (DepMatrix.size() > MaxMemInstrCount) {
-            DEBUG(dbgs() << "Cannot handle more than " << MaxMemInstrCount
-                         << " dependencies inside loop\n");
-            return false;
-          }
+        DepMatrix.push_back(Dep);
+        if (DepMatrix.size() > MaxMemInstrCount) {
+          DEBUG(dbgs() << "Cannot handle more than " << MaxMemInstrCount
+                       << " dependencies inside loop\n");
+          return false;
         }
       }
     }
Index: test/Transforms/LoopInterchange/interchange.ll
===================================================================
--- test/Transforms/LoopInterchange/interchange.ll
+++ test/Transforms/LoopInterchange/interchange.ll
@@ -555,3 +555,195 @@
 ; CHECK:   for.end17:                                        ; preds = %for.inc15
 ; CHECK:     ret void
 
+;;-----------------------------------Test case 09-------------------------------
+;; Test that a flow dependency in outer loop doesn't prevent interchange in
+;; loops i and j.
+;;
+;;  for (int k = 0; k < 100; ++k) {
+;;    T[k] = fn1();
+;;    for (int i = 0; i < 1000; ++i)
+;;      for(int j = 1; j < 1000; ++j)
+;;        Arr[j][i] = Arr[j][i]+k;
+;;    fn2(T[k]);
+;;  }
+
+@T = internal global [100 x double] zeroinitializer, align 4
+@Arr = internal global [1000 x [1000 x i32]] zeroinitializer, align 4
+
+define void @interchange_09(i32 %k) {
+entry:
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup4
+  ret void
+
+for.body:                                         ; preds = %for.cond.cleanup4, %entry
+  %indvars.iv45 = phi i64 [ 0, %entry ], [ %indvars.iv.next46, %for.cond.cleanup4 ]
+  %call = call double @fn1()
+  %arrayidx = getelementptr inbounds [100 x double], [100 x double]* @T, i64 0, i64 %indvars.iv45
+  store double %call, double* %arrayidx, align 8
+  br label %for.cond6.preheader
+
+for.cond6.preheader:                              ; preds = %for.cond.cleanup8, %for.body
+  %indvars.iv42 = phi i64 [ 0, %for.body ], [ %indvars.iv.next43, %for.cond.cleanup8 ]
+  br label %for.body9
+
+for.cond.cleanup4:                                ; preds = %for.cond.cleanup8
+  %tmp = load double, double* %arrayidx, align 8
+  call void @fn2(double %tmp)
+  %indvars.iv.next46 = add nuw nsw i64 %indvars.iv45, 1
+  %exitcond47 = icmp ne i64 %indvars.iv.next46, 100
+  br i1 %exitcond47, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup8:                                ; preds = %for.body9
+  %indvars.iv.next43 = add nuw nsw i64 %indvars.iv42, 1
+  %exitcond44 = icmp ne i64 %indvars.iv.next43, 1000
+  br i1 %exitcond44, label %for.cond6.preheader, label %for.cond.cleanup4
+
+for.body9:                                        ; preds = %for.body9, %for.cond6.preheader
+  %indvars.iv = phi i64 [ 1, %for.cond6.preheader ], [ %indvars.iv.next, %for.body9 ]
+  %arrayidx13 = getelementptr inbounds [1000 x [1000 x i32]], [1000 x [1000 x i32]]* @Arr, i64 0, i64 %indvars.iv, i64 %indvars.iv42
+  %tmp1 = load i32, i32* %arrayidx13, align 4
+  %tmp2 = trunc i64 %indvars.iv45 to i32
+  %add = add nsw i32 %tmp1, %tmp2
+  store i32 %add, i32* %arrayidx13, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp ne i64 %indvars.iv.next, 1000
+  br i1 %exitcond, label %for.body9, label %for.cond.cleanup8
+}
+
+declare double @fn1()
+declare void @fn2(double)
+
+
+
+
+
+;; After interchange %indvars.iv (j) should increment as the middle loop.
+;; After interchange %indvars.iv42 (i) should increment with the inner most loop.
+
+; CHECK-LABEL: @interchange_09
+
+; CHECK: for.body:
+; CHECK:   %indvars.iv45 = phi i64 [ %indvars.iv.next46, %for.cond.cleanup4 ], [ 0, %for.body.preheader ]
+; CHECK:   %call = call double @fn1()
+; CHECK:   %arrayidx = getelementptr inbounds [100 x double], [100 x double]* @T, i64 0, i64 %indvars.iv45
+; CHECK:   store double %call, double* %arrayidx, align 8
+; CHECK:   br label %for.body9.preheader
+
+; CHECK: for.cond6.preheader.preheader:
+; CHECK:   br label %for.cond6.preheader
+
+; CHECK: for.cond6.preheader:
+; CHECK:   %indvars.iv42 = phi i64 [ %indvars.iv.next43, %for.cond.cleanup8 ], [ 0, %for.cond6.preheader.preheader ]
+; CHECK:   br label %for.body9.split1
+
+; CHECK: for.body9.preheader:
+; CHECK:   br label %for.body9
+
+; CHECK: for.cond.cleanup4:
+; CHECK:   %tmp = load double, double* %arrayidx, align 8
+; CHECK:   call void @fn2(double %tmp)
+; CHECK:   %indvars.iv.next46 = add nuw nsw i64 %indvars.iv45, 1
+; CHECK:   %exitcond47 = icmp ne i64 %indvars.iv.next46, 100
+; CHECK:   br i1 %exitcond47, label %for.body, label %for.cond.cleanup
+
+; CHECK: for.cond.cleanup8:
+; CHECK:   %indvars.iv.next43 = add nuw nsw i64 %indvars.iv42, 1
+; CHECK:   %exitcond44 = icmp ne i64 %indvars.iv.next43, 1000
+; CHECK:   br i1 %exitcond44, label %for.cond6.preheader, label %for.body9.split
+
+; CHECK: for.body9:
+; CHECK:   %indvars.iv = phi i64 [ %indvars.iv.next, %for.body9.split ], [ 1, %for.body9.preheader ]
+; CHECK:   br label %for.cond6.preheader.preheader
+
+; CHECK: for.body9.split1:
+; CHECK:   %arrayidx13 = getelementptr inbounds [1000 x [1000 x i32]], [1000 x [1000 x i32]]* @Arr, i64 0, i64 %indvars.iv, i64 %indvars.iv42
+; CHECK:   store i32 %add, i32* %arrayidx13, align 4
+; CHECK:   br label %for.cond.cleanup8
+
+; CHECK: for.body9.split:
+; CHECK:   %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+; CHECK:   %exitcond = icmp ne i64 %indvars.iv.next, 1000
+; CHECK:   br i1 %exitcond, label %for.body9, label %for.cond.cleanup4
+
+
+;;-----------------------------------Test case 10-------------------------------
+;; Test to make sure we can handle output dependencies.
+;;
+;;  for (int i = 0; i < 2; ++i)
+;;    for(int j = 0; j < 3; ++j) {
+;;      A[j][i] = i;
+;;      A[j][i+1] = j;
+;;    }
+
+@A10 = local_unnamed_addr global [3 x [3 x i32]] zeroinitializer, align 16
+
+define void @interchange_10() {
+entry:
+  br label %for.cond1.preheader
+
+for.cond.loopexit:                                ; preds = %for.body4
+  %exitcond28 = icmp ne i64 %indvars.iv.next27, 2
+  br i1 %exitcond28, label %for.cond1.preheader, label %for.cond.cleanup
+
+for.cond1.preheader:                              ; preds = %for.cond.loopexit, %entry
+  %indvars.iv26 = phi i64 [ 0, %entry ], [ %indvars.iv.next27, %for.cond.loopexit ]
+  %indvars.iv.next27 = add nuw nsw i64 %indvars.iv26, 1
+  br label %for.body4
+
+for.cond.cleanup:                                 ; preds = %for.cond.loopexit
+  ret void
+
+for.body4:                                        ; preds = %for.body4, %for.cond1.preheader
+  %indvars.iv = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next, %for.body4 ]
+  %arrayidx6 = getelementptr inbounds [3 x [3 x i32]], [3 x [3 x i32]]* @A10, i64 0, i64 %indvars.iv, i64 %indvars.iv26
+  %tmp = trunc i64 %indvars.iv26 to i32
+  store i32 %tmp, i32* %arrayidx6, align 4
+  %arrayidx10 = getelementptr inbounds [3 x [3 x i32]], [3 x [3 x i32]]* @A10, i64 0, i64 %indvars.iv, i64 %indvars.iv.next27
+  %tmp1 = trunc i64 %indvars.iv to i32
+  store i32 %tmp1, i32* %arrayidx10, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp ne i64 %indvars.iv.next, 3
+  br i1 %exitcond, label %for.body4, label %for.cond.loopexit
+}
+
+; CHECK-LABEL: @interchange_10
+; CHECK: entry:
+; CHECK:   br label %for.body4.preheader
+
+; CHECK: for.cond1.preheader.preheader:
+; CHECK:   br label %for.cond1.preheader
+
+; CHECK: for.cond.loopexit:
+; CHECK:   %exitcond28 = icmp ne i64 %indvars.iv.next27, 2
+; CHECK:   br i1 %exitcond28, label %for.cond1.preheader, label %for.body4.split
+
+; CHECK: for.cond1.preheader:
+; CHECK:   %indvars.iv26 = phi i64 [ %indvars.iv.next27, %for.cond.loopexit ], [ 0, %for.cond1.preheader.preheader ]
+; CHECK:   %indvars.iv.next27 = add nuw nsw i64 %indvars.iv26, 1
+; CHECK:   br label %for.body4.split1
+
+; CHECK: for.body4.preheader:
+; CHECK:   br label %for.body4
+
+; CHECK: for.cond.cleanup:
+; CHECK:   ret void
+
+; CHECK: for.body4:
+; CHECK:   %indvars.iv = phi i64 [ %indvars.iv.next, %for.body4.split ], [ 0, %for.body4.preheader ]
+; CHECK:   br label %for.cond1.preheader.preheader
+
+; CHECK: for.body4.split1:
+; CHECK:   %arrayidx6 = getelementptr inbounds [3 x [3 x i32]], [3 x [3 x i32]]* @A10, i64 0, i64 %indvars.iv, i64 %indvars.iv26
+; CHECK:   %tmp = trunc i64 %indvars.iv26 to i32
+; CHECK:   store i32 %tmp, i32* %arrayidx6, align 4
+; CHECK:   %arrayidx10 = getelementptr inbounds [3 x [3 x i32]], [3 x [3 x i32]]* @A10, i64 0, i64 %indvars.iv, i64 %indvars.iv.next27
+; CHECK:   %tmp1 = trunc i64 %indvars.iv to i32
+; CHECK:   store i32 %tmp1, i32* %arrayidx10, align 4
+; CHECK:   br label %for.cond.loopexit
+
+; CHECK: for.body4.split:
+; CHECK:   %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+; CHECK:   %exitcond = icmp ne i64 %indvars.iv.next, 3
+; CHECK:   br i1 %exitcond, label %for.body4, label %for.cond.cleanup