diff --git a/llvm/lib/Transforms/Scalar/LoopRerollPass.cpp b/llvm/lib/Transforms/Scalar/LoopRerollPass.cpp
--- a/llvm/lib/Transforms/Scalar/LoopRerollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRerollPass.cpp
@@ -191,13 +191,14 @@
 
     using SmallInstructionVector = SmallVector<Instruction *, 16>;
     using SmallInstructionSet = SmallPtrSet<Instruction *, 16>;
+    using TinyInstructionVector = SmallVector<Instruction *, 1>;
 
     // Map between induction variable and its increment
     DenseMap<Instruction *, int64_t> IVToIncMap;
 
-    // For loop with multiple induction variable, remember the one used only to
+    // For loop with multiple induction variables, remember the ones used only to
     // control the loop.
-    Instruction *LoopControlIV;
+    TinyInstructionVector LoopControlIVs;
 
     // A chain of isomorphic instructions, identified by a single-use PHI
     // representing a reduction. Only the last value may be used outside the
@@ -386,10 +387,10 @@
                      TargetLibraryInfo *TLI, DominatorTree *DT, LoopInfo *LI,
                      bool PreserveLCSSA,
                      DenseMap<Instruction *, int64_t> &IncrMap,
-                     Instruction *LoopCtrlIV)
+                     TinyInstructionVector LoopCtrlIVs)
           : Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI), DT(DT), LI(LI),
             PreserveLCSSA(PreserveLCSSA), IV(IV), IVToIncMap(IncrMap),
-            LoopControlIV(LoopCtrlIV) {}
+            LoopControlIVs(LoopCtrlIVs) {}
 
       /// Stage 1: Find all the DAG roots for the induction variable.
       bool findRoots();
@@ -468,7 +469,7 @@
       // Map between induction variable and its increment
       DenseMap<Instruction *, int64_t> &IVToIncMap;
 
-      Instruction *LoopControlIV;
+      TinyInstructionVector LoopControlIVs;
     };
 
     // Check if it is a compare-like instruction whose user is a branch
@@ -577,33 +578,28 @@
 // be possible to reroll the loop.
 void LoopReroll::collectPossibleIVs(Loop *L,
                                     SmallInstructionVector &PossibleIVs) {
-  BasicBlock *Header = L->getHeader();
-  for (BasicBlock::iterator I = Header->begin(),
-       IE = Header->getFirstInsertionPt(); I != IE; ++I) {
-    if (!isa<PHINode>(I))
-      continue;
-    if (!I->getType()->isIntegerTy() && !I->getType()->isPointerTy())
+  for (Instruction &IV : L->getHeader()->phis()) {
+    if (!IV.getType()->isIntegerTy() && !IV.getType()->isPointerTy())
       continue;
 
     if (const SCEVAddRecExpr *PHISCEV =
-            dyn_cast<SCEVAddRecExpr>(SE->getSCEV(&*I))) {
+            dyn_cast<SCEVAddRecExpr>(SE->getSCEV(&IV))) {
       if (PHISCEV->getLoop() != L)
         continue;
       if (!PHISCEV->isAffine())
         continue;
-      auto IncSCEV = dyn_cast<SCEVConstant>(PHISCEV->getStepRecurrence(*SE));
+      const auto *IncSCEV = dyn_cast<SCEVConstant>(PHISCEV->getStepRecurrence(*SE));
       if (IncSCEV) {
-        IVToIncMap[&*I] = IncSCEV->getValue()->getSExtValue();
-        LLVM_DEBUG(dbgs() << "LRR: Possible IV: " << *I << " = " << *PHISCEV
+        IVToIncMap[&IV] = IncSCEV->getValue()->getSExtValue();
+        LLVM_DEBUG(dbgs() << "LRR: Possible IV: " << IV << " = " << *PHISCEV
                           << "\n");
 
-        if (isLoopControlIV(L, &*I)) {
-          assert(!LoopControlIV && "Found two loop control only IV");
-          LoopControlIV = &(*I);
-          LLVM_DEBUG(dbgs() << "LRR: Possible loop control only IV: " << *I
+        if (isLoopControlIV(L, &IV)) {
+          LoopControlIVs.push_back(&IV);
+          LLVM_DEBUG(dbgs() << "LRR: Loop control only IV: " << IV
                             << " = " << *PHISCEV << "\n");
         } else
-          PossibleIVs.push_back(&*I);
+          PossibleIVs.push_back(&IV);
       }
     }
   }
@@ -1184,7 +1180,7 @@
   // Make sure we mark loop-control-only PHIs as used in all iterations. See
   // comment above LoopReroll::isLoopControlIV for more information.
   BasicBlock *Header = L->getHeader();
-  if (LoopControlIV && LoopControlIV != IV) {
+  for (Instruction *LoopControlIV : LoopControlIVs) {
     for (auto *U : LoopControlIV->users()) {
       Instruction *IVUser = dyn_cast<Instruction>(U);
       // IVUser could be loop increment or compare
@@ -1633,7 +1629,7 @@
                         const SCEV *BackedgeTakenCount,
                         ReductionTracker &Reductions) {
   DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI, DT, LI, PreserveLCSSA,
-                          IVToIncMap, LoopControlIV);
+                          IVToIncMap, LoopControlIVs);
 
   if (!DAGRoots.findRoots())
     return false;
@@ -1676,7 +1672,7 @@
   // reroll (there may be several possible options).
   SmallInstructionVector PossibleIVs;
   IVToIncMap.clear();
-  LoopControlIV = nullptr;
+  LoopControlIVs.clear();
   collectPossibleIVs(L, PossibleIVs);
 
   if (PossibleIVs.empty()) {
diff --git a/llvm/test/Transforms/LoopReroll/complex_reroll.ll b/llvm/test/Transforms/LoopReroll/complex_reroll.ll
--- a/llvm/test/Transforms/LoopReroll/complex_reroll.ll
+++ b/llvm/test/Transforms/LoopReroll/complex_reroll.ll
@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -S -passes=loop-reroll   %s | FileCheck %s
 declare i32 @goo(i32, i32)
 
@@ -5,21 +6,30 @@
 @aaa = global [16 x i8] c"\01\02\03\04\05\06\07\08\09\0A\0B\0C\0D\0E\0F\10", align 1
 
 define i32 @test1(i32 %len) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[WHILE_BODY:%.*]]
+; CHECK:       while.body:
+; CHECK-NEXT:    [[INDVAR:%.*]] = phi i64 [ [[INDVAR_NEXT:%.*]], [[WHILE_BODY]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[SUM44_020:%.*]] = phi i64 [ 0, [[ENTRY]] ], [ [[ADD:%.*]], [[WHILE_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = trunc i64 [[INDVAR]] to i32
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr [16 x i8], [16 x i8]* @aaa, i64 0, i64 [[INDVAR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, i8* [[SCEVGEP]], align 1
+; CHECK-NEXT:    [[CONV:%.*]] = zext i8 [[TMP1]] to i64
+; CHECK-NEXT:    [[ADD]] = add i64 [[CONV]], [[SUM44_020]]
+; CHECK-NEXT:    [[INDVAR_NEXT]] = add i64 [[INDVAR]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[TMP0]], 15
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[WHILE_END:%.*]], label [[WHILE_BODY]]
+; CHECK:       while.end:
+; CHECK-NEXT:    [[ADD9_LCSSA:%.*]] = phi i64 [ [[ADD]], [[WHILE_BODY]] ]
+; CHECK-NEXT:    [[CONV11:%.*]] = trunc i64 [[ADD9_LCSSA]] to i32
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @goo(i32 0, i32 [[CONV11]])
+; CHECK-NEXT:    unreachable
+;
 entry:
   br label %while.body
 
 while.body:
-;CHECK-LABEL: while.body:
-;CHECK-NEXT:    %indvar = phi i64 [ %indvar.next, %while.body ], [ 0, %entry ]
-;CHECK-NEXT:    %sum44.020 = phi i64 [ 0, %entry ], [ %add, %while.body ]
-;CHECK-NEXT:    %0 = trunc i64 %indvar to i32
-;CHECK-NEXT:    %scevgep = getelementptr [16 x i8], [16 x i8]* @aaa, i64 0, i64 %indvar
-;CHECK-NEXT:    [[T2:%[0-9]+]] = load i8, i8* %scevgep, align 1
-;CHECK-NEXT:    %conv = zext i8 [[T2]] to i64
-;CHECK-NEXT:    %add = add i64 %conv, %sum44.020
-;CHECK-NEXT:    %indvar.next = add i64 %indvar, 1
-;CHECK-NEXT:    %exitcond = icmp eq i32 %0, 15
-;CHECK-NEXT:    br i1 %exitcond, label %while.end, label %while.body
 
   %dec22 = phi i32 [ 4, %entry ], [ %dec, %while.body ]
   %buf.021 = phi i8* [ getelementptr inbounds ([16 x i8], [16 x i8]* @aaa, i64 0, i64 0), %entry ], [ %add.ptr, %while.body ]
@@ -51,6 +61,33 @@
 }
 
 define i32 @test2(i32 %N, i32* nocapture readonly %a, i32 %S) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP_9:%.*]] = icmp sgt i32 [[N:%.*]], 0
+; CHECK-NEXT:    br i1 [[CMP_9]], label [[FOR_BODY_LR_PH:%.*]], label [[FOR_COND_CLEANUP:%.*]]
+; CHECK:       for.body.lr.ph:
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[TMP0]], 1
+; CHECK-NEXT:    [[TMP2:%.*]] = shl nuw i32 [[TMP1]], 1
+; CHECK-NEXT:    [[TMP3:%.*]] = add nuw nsw i32 [[TMP2]], 1
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.cond.for.cond.cleanup_crit_edge:
+; CHECK-NEXT:    [[ADD2_LCSSA:%.*]] = phi i32 [ [[ADD:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    br label [[FOR_COND_CLEANUP]]
+; CHECK:       for.cond.cleanup:
+; CHECK-NEXT:    [[S_ADDR_0_LCSSA:%.*]] = phi i32 [ [[ADD2_LCSSA]], [[FOR_COND_FOR_COND_CLEANUP_CRIT_EDGE:%.*]] ], [ [[S:%.*]], [[ENTRY:%.*]] ]
+; CHECK-NEXT:    ret i32 [[S_ADDR_0_LCSSA]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[INDVAR:%.*]] = phi i64 [ [[INDVAR_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_BODY_LR_PH]] ]
+; CHECK-NEXT:    [[S_ADDR_011:%.*]] = phi i32 [ [[S]], [[FOR_BODY_LR_PH]] ], [ [[ADD]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[TMP4:%.*]] = trunc i64 [[INDVAR]] to i32
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr i32, i32* [[A:%.*]], i64 [[INDVAR]]
+; CHECK-NEXT:    [[TMP5:%.*]] = load i32, i32* [[SCEVGEP]], align 4
+; CHECK-NEXT:    [[ADD]] = add nsw i32 [[TMP5]], [[S_ADDR_011]]
+; CHECK-NEXT:    [[INDVAR_NEXT]] = add i64 [[INDVAR]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[TMP4]], [[TMP3]]
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[FOR_COND_FOR_COND_CLEANUP_CRIT_EDGE]], label [[FOR_BODY]]
+;
 entry:
   %cmp.9 = icmp sgt i32 %N, 0
   br i1 %cmp.9, label %for.body.lr.ph, label %for.cond.cleanup
@@ -66,16 +103,6 @@
   ret i32 %S.addr.0.lcssa
 
 for.body:
-;CHECK-LABEL: for.body:
-;CHECK-NEXT:    %indvar = phi i64 [ %indvar.next, %for.body ], [ 0, %for.body.lr.ph ]
-;CHECK-NEXT:    %S.addr.011 = phi i32 [ %S, %for.body.lr.ph ], [ %add, %for.body ]
-;CHECK-NEXT:    %4 = trunc i64 %indvar to i32
-;CHECK-NEXT:    %scevgep = getelementptr i32, i32* %a, i64 %indvar
-;CHECK-NEXT:    %5 = load i32, i32* %scevgep, align 4
-;CHECK-NEXT:    %add = add nsw i32 %5, %S.addr.011
-;CHECK-NEXT:    %indvar.next = add i64 %indvar, 1
-;CHECK-NEXT:    %exitcond = icmp eq i32 %4, %3
-;CHECK-NEXT:    br i1 %exitcond, label %for.cond.for.cond.cleanup_crit_edge, label %for.body
 
   %i.012 = phi i32 [ 0, %for.body.lr.ph ], [ %add3, %for.body ]
   %S.addr.011 = phi i32 [ %S, %for.body.lr.ph ], [ %add2, %for.body ]
@@ -92,6 +119,34 @@
 }
 
 define i32 @test3(i32* nocapture readonly %buf, i32 %len) #0 {
+; CHECK-LABEL: @test3(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[CMP10:%.*]] = icmp sgt i32 [[LEN:%.*]], 1
+; CHECK-NEXT:    br i1 [[CMP10]], label [[WHILE_BODY_PREHEADER:%.*]], label [[WHILE_END:%.*]]
+; CHECK:       while.body.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[LEN]], -2
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[TMP0]], 1
+; CHECK-NEXT:    [[TMP2:%.*]] = shl nuw i32 [[TMP1]], 1
+; CHECK-NEXT:    [[TMP3:%.*]] = add nuw nsw i32 [[TMP2]], 1
+; CHECK-NEXT:    br label [[WHILE_BODY:%.*]]
+; CHECK:       while.body:
+; CHECK-NEXT:    [[INDVAR:%.*]] = phi i64 [ [[INDVAR_NEXT:%.*]], [[WHILE_BODY]] ], [ 0, [[WHILE_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[S_012:%.*]] = phi i32 [ [[ADD:%.*]], [[WHILE_BODY]] ], [ undef, [[WHILE_BODY_PREHEADER]] ]
+; CHECK-NEXT:    [[TMP4:%.*]] = trunc i64 [[INDVAR]] to i32
+; CHECK-NEXT:    [[TMP5:%.*]] = mul nsw i64 [[INDVAR]], -1
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr i32, i32* [[BUF:%.*]], i64 [[TMP5]]
+; CHECK-NEXT:    [[TMP6:%.*]] = load i32, i32* [[SCEVGEP]], align 4
+; CHECK-NEXT:    [[ADD]] = add nsw i32 [[TMP6]], [[S_012]]
+; CHECK-NEXT:    [[INDVAR_NEXT]] = add i64 [[INDVAR]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[TMP4]], [[TMP3]]
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[WHILE_END_LOOPEXIT:%.*]], label [[WHILE_BODY]]
+; CHECK:       while.end.loopexit:
+; CHECK-NEXT:    [[ADD2_LCSSA:%.*]] = phi i32 [ [[ADD]], [[WHILE_BODY]] ]
+; CHECK-NEXT:    br label [[WHILE_END]]
+; CHECK:       while.end:
+; CHECK-NEXT:    [[S_0_LCSSA:%.*]] = phi i32 [ undef, [[ENTRY:%.*]] ], [ [[ADD2_LCSSA]], [[WHILE_END_LOOPEXIT]] ]
+; CHECK-NEXT:    ret i32 [[S_0_LCSSA]]
+;
 entry:
   %cmp10 = icmp sgt i32 %len, 1
   br i1 %cmp10, label %while.body.preheader, label %while.end
@@ -100,17 +155,6 @@
   br label %while.body
 
 while.body:                                       ; preds = %while.body.preheader, %while.body
-;CHECK-LABEL: while.body:
-;CHECK-NEXT:  %indvar = phi i64 [ %indvar.next, %while.body ], [ 0, %while.body.preheader ]
-;CHECK-NEXT:  %S.012 = phi i32 [ %add, %while.body ], [ undef, %while.body.preheader ]
-;CHECK-NEXT:  %4 = trunc i64 %indvar to i32
-;CHECK-NEXT:  %5 = mul nsw i64 %indvar, -1
-;CHECK-NEXT:  %scevgep = getelementptr i32, i32* %buf, i64 %5
-;CHECK-NEXT:  %6 = load i32, i32* %scevgep, align 4
-;CHECK-NEXT:  %add = add nsw i32 %6, %S.012
-;CHECK-NEXT:  %indvar.next = add i64 %indvar, 1
-;CHECK-NEXT:  %exitcond = icmp eq i32 %4, %3
-;CHECK-NEXT:  br i1 %exitcond, label %while.end.loopexit, label %while.body
 
   %i.013 = phi i32 [ %sub, %while.body ], [ %len, %while.body.preheader ]
   %S.012 = phi i32 [ %add2, %while.body ], [ undef, %while.body.preheader ]
@@ -133,3 +177,60 @@
   ret i32 %S.0.lcssa
 }
 
+define i32 @test4(i32 %len) {
+; CHECK-LABEL: @test4(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[WHILE_BODY:%.*]]
+; CHECK:       while.body:
+; CHECK-NEXT:    [[INDVAR:%.*]] = phi i64 [ [[INDVAR_NEXT:%.*]], [[WHILE_BODY]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[SUM44_020:%.*]] = phi i64 [ 0, [[ENTRY]] ], [ [[ADD:%.*]], [[WHILE_BODY]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = trunc i64 [[INDVAR]] to i32
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr [16 x i8], [16 x i8]* @aaa, i64 0, i64 [[INDVAR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, i8* [[SCEVGEP]], align 1
+; CHECK-NEXT:    [[CONV:%.*]] = zext i8 [[TMP1]] to i64
+; CHECK-NEXT:    [[ADD]] = add i64 [[CONV]], [[SUM44_020]]
+; CHECK-NEXT:    [[INDVAR_NEXT]] = add i64 [[INDVAR]], 1
+; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp eq i32 [[TMP0]], 23
+; CHECK-NEXT:    br i1 [[EXITCOND]], label [[WHILE_END:%.*]], label [[WHILE_BODY]]
+; CHECK:       while.end:
+; CHECK-NEXT:    [[ADD9_LCSSA:%.*]] = phi i64 [ [[ADD]], [[WHILE_BODY]] ]
+; CHECK-NEXT:    [[CONV11:%.*]] = trunc i64 [[ADD9_LCSSA]] to i32
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @goo(i32 0, i32 [[CONV11]])
+; CHECK-NEXT:    unreachable
+;
+entry:
+  br label %while.body
+
+while.body:
+  %a = phi i32 [ 4, %entry ], [ %a.next, %while.body ]
+  %b = phi i32 [ 6, %entry ], [ %b.next, %while.body ]
+  %buf.021 = phi i8* [ getelementptr inbounds ([16 x i8], [16 x i8]* @aaa, i64 0, i64 0), %entry ], [ %add.ptr, %while.body ]
+  %sum44.020 = phi i64 [ 0, %entry ], [ %add9, %while.body ]
+  %0 = load i8, i8* %buf.021, align 1
+  %conv = zext i8 %0 to i64
+  %add = add i64 %conv, %sum44.020
+  %arrayidx1 = getelementptr inbounds i8, i8* %buf.021, i64 1
+  %1 = load i8, i8* %arrayidx1, align 1
+  %conv2 = zext i8 %1 to i64
+  %add3 = add i64 %add, %conv2
+  %arrayidx4 = getelementptr inbounds i8, i8* %buf.021, i64 2
+  %2 = load i8, i8* %arrayidx4, align 1
+  %conv5 = zext i8 %2 to i64
+  %add6 = add i64 %add3, %conv5
+  %arrayidx7 = getelementptr inbounds i8, i8* %buf.021, i64 3
+  %3 = load i8, i8* %arrayidx7, align 1
+  %conv8 = zext i8 %3 to i64
+  %add9 = add i64 %add6, %conv8
+  %add.ptr = getelementptr inbounds i8, i8* %buf.021, i64 4
+  %a.next = add nsw i32 %a, -1
+  %b.next = add nsw i32 %b, -1
+  %cond = add nsw i32 %a, %b
+  %tobool = icmp eq i32 %cond, 0
+  br i1 %tobool, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body
+  %conv11 = trunc i64 %add9 to i32
+  %call = tail call i32 @goo(i32 0, i32 %conv11)
+  unreachable
+}
+