Index: lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -30,6 +30,7 @@
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Metadata.h"
+#include "llvm/IR/PatternMatch.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -46,6 +47,7 @@
 #include <limits>
 
 using namespace llvm;
+using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "loop-unroll"
 
@@ -136,6 +138,49 @@
   return ToInvariance;
 }
 
+// Return the number of iterations to peel off that make conditions in the
+// body true/false. For example, if we peel 2 iterations off the loop below,
+// the condition i < 2 can be evaluated at compile time.
+//  for (i = 0; i < n; i++)
+//    if (i < 2)
+//      ..
+//    else
+//      ..
+//   }
+//
+// Currently only comparisons of the form IndVar < Constant are supported.
+static unsigned countToEliminateCompares(Loop *L, unsigned MaxPeelCount) {
+  unsigned DesiredPeelCount = 0;
+  PHINode *IndVar = L->getCanonicalInductionVariable();
+  if (!IndVar)
+    return 0;
+
+  for (auto *BB : L->blocks()) {
+    auto *BI = dyn_cast<BranchInst>(BB->getTerminator());
+    if (!BI || BI->isUnconditional())
+      continue;
+    Value *Condition = BI->getCondition();
+    ConstantInt *UpperBound;
+    Value *Var;
+    CmpInst::Predicate Pred;
+    if (!Condition || !match(Condition, m_ICmp(Pred, m_Value(Var),
+                                               m_ConstantInt(UpperBound))))
+      continue;
+
+    if (UpperBound->isNegative())
+      continue;
+
+    if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT) &&
+        Var == IndVar) {
+      unsigned Bound = UpperBound->getLimitedValue(MaxPeelCount + 1);
+      if (Bound <= MaxPeelCount)
+        DesiredPeelCount = std::max(DesiredPeelCount, Bound);
+    }
+  }
+
+  return DesiredPeelCount;
+}
+
 // Return the number of iterations we want to peel off.
 void llvm::computePeelCount(Loop *L, unsigned LoopSize,
                             TargetTransformInfo::UnrollingPreferences &UP,
@@ -170,10 +215,15 @@
       if (ToInvariance != InfiniteIterationsToInvariance)
         DesiredPeelCount = std::max(DesiredPeelCount, ToInvariance);
     }
+
+    // Pay respect to limitations implied by loop size and the max peel count.
+    unsigned MaxPeelCount = UnrollPeelMaxCount;
+    MaxPeelCount = std::min(MaxPeelCount, UP.Threshold / LoopSize - 1);
+
+    DesiredPeelCount =
+        std::max(DesiredPeelCount, countToEliminateCompares(L, MaxPeelCount));
+
     if (DesiredPeelCount > 0) {
-      // Pay respect to limitations implied by loop size and the max peel count.
-      unsigned MaxPeelCount = UnrollPeelMaxCount;
-      MaxPeelCount = std::min(MaxPeelCount, UP.Threshold / LoopSize - 1);
       DesiredPeelCount = std::min(DesiredPeelCount, MaxPeelCount);
       // Consider max peel count limitation.
       assert(DesiredPeelCount > 0 && "Wrong loop size estimation?");
Index: test/Transforms/LoopUnroll/peel-loop-conditions.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnroll/peel-loop-conditions.ll
@@ -0,0 +1,75 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -loop-unroll -verify-dom-info -simplifycfg | FileCheck %s
+
+declare void @f1()
+declare void @f2()
+
+define void @basic(i32 %k) {
+; CHECK-LABEL: @basic(
+; CHECK-NEXT:  for.body.lr.ph:
+; CHECK-NEXT:    [[CMP1_PEEL:%.*]] = icmp ult i32 0, 2
+; CHECK-NEXT:    br i1 [[CMP1_PEEL]], label [[IF_THEN_PEEL:%.*]], label [[IF_ELSE_PEEL:%.*]]
+; CHECK:       if.else.peel:
+; CHECK-NEXT:    call void @f2()
+; CHECK-NEXT:    br label [[FOR_INC_PEEL:%.*]]
+; CHECK:       if.then.peel:
+; CHECK-NEXT:    call void @f1()
+; CHECK-NEXT:    br label [[FOR_INC_PEEL]]
+; CHECK:       for.inc.peel:
+; CHECK-NEXT:    [[INC_PEEL:%.*]] = add nsw i32 0, 1
+; CHECK-NEXT:    [[CMP_PEEL:%.*]] = icmp slt i32 [[INC_PEEL]], [[K:%.*]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL]], label [[FOR_BODY_PEEL2:%.*]], label [[FOR_END:%.*]]
+; CHECK:       for.body.peel2:
+; CHECK-NEXT:    [[CMP1_PEEL3:%.*]] = icmp ult i32 [[INC_PEEL]], 2
+; CHECK-NEXT:    br i1 [[CMP1_PEEL3]], label [[IF_THEN_PEEL5:%.*]], label [[IF_ELSE_PEEL4:%.*]]
+; CHECK:       if.else.peel4:
+; CHECK-NEXT:    call void @f2()
+; CHECK-NEXT:    br label [[FOR_INC_PEEL6:%.*]]
+; CHECK:       if.then.peel5:
+; CHECK-NEXT:    call void @f1()
+; CHECK-NEXT:    br label [[FOR_INC_PEEL6]]
+; CHECK:       for.inc.peel6:
+; CHECK-NEXT:    [[INC_PEEL7:%.*]] = add nsw i32 [[INC_PEEL]], 1
+; CHECK-NEXT:    [[CMP_PEEL8:%.*]] = icmp slt i32 [[INC_PEEL7]], [[K]]
+; CHECK-NEXT:    br i1 [[CMP_PEEL8]], label [[FOR_BODY:%.*]], label [[FOR_END]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_05:%.*]] = phi i32 [ [[INC:%.*]], [[FOR_INC:%.*]] ], [ [[INC_PEEL7]], [[FOR_INC_PEEL6]] ]
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp ult i32 [[I_05]], 2
+; CHECK-NEXT:    br i1 [[CMP1]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @f1()
+; CHECK-NEXT:    br label [[FOR_INC]]
+; CHECK:       if.else:
+; CHECK-NEXT:    call void @f2()
+; CHECK-NEXT:    br label [[FOR_INC]]
+; CHECK:       for.inc:
+; CHECK-NEXT:    [[INC]] = add nsw i32 [[I_05]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[INC]], [[K]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END]], !llvm.loop !0
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+for.body.lr.ph:
+  br label %for.body
+
+for.body:
+  %i.05 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
+  %cmp1 = icmp ult i32 %i.05, 2
+  br i1 %cmp1, label %if.then, label %if.else
+
+if.then:
+  call void @f1()
+  br label %for.inc
+
+if.else:
+  call void @f2()
+  br label %for.inc
+
+for.inc:
+  %inc = add nsw i32 %i.05, 1
+  %cmp = icmp slt i32 %inc, %k
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:
+  ret void
+}