[Unroll] Rework the naming and structure of the new unroll heuristics.
authorChandler Carruth <chandlerc@gmail.com>
Fri, 5 Jun 2015 17:01:43 +0000 (17:01 +0000)
committerChandler Carruth <chandlerc@gmail.com>
Fri, 5 Jun 2015 17:01:43 +0000 (17:01 +0000)
The new naming is (to me) much easier to understand. Here is a summary
of the new state of the world:

- '*Threshold' is the threshold for full unrolling. It is measured
  against the estimated unrolled cost as computed by getUserCost in TTI
  (or CodeMetrics, etc). We will exceed this threshold when unrolling
  loops where unrolling exposes a significant degree of simplification
  of the logic within the loop.
- '*PercentDynamicCostSavedThreshold' is the percentage of the loop's
  estimated dynamic execution cost which needs to be saved by unrolling
  to apply a discount to the estimated unrolled cost.
- '*DynamicCostSavingsDiscount' is the discount applied to the estimated
  unrolling cost when the dynamic savings are expected to be high.

When actually analyzing the loop, we now produce both an estimated
unrolled cost, and an estimated rolled cost. The rolled cost is notably
a dynamic estimate based on our analysis of the expected execution of
each iteration.

While we're still working to build up the infrastructure for making
these estimates, to me it is much more clear *how* to make them better
when they have reasonably descriptive names. For example, we may want to
apply estimated (from heuristics or profiles) dynamic execution weights
to the *dynamic* cost estimates. If we start doing that, we would also
need to track the static unrolled cost and the dynamic unrolled cost, as
only the latter could reasonably be weighted by profile information.

This patch is sadly not without functionality change for the new unroll
analysis logic. Buried in the heuristic management were several things
that surprised me. For example, we never subtracted the optimized
instruction count off when comparing against the unroll heursistics!
I don't know if this just got lost somewhere along the way or what, but
with the new accounting of things, this is much easier to keep track of
and we use the post-simplification cost estimate to compare to the
thresholds, and use the dynamic cost reduction ratio to select whether
we can exceed the baseline threshold.

The old values of these flags also don't necessarily make sense. My
impression is that none of these thresholds or discounts have been tuned
yet, and so they're just arbitrary placehold numbers. As such, I've not
bothered to adjust for the fact that this is now a discount and not
a tow-tier threshold model. We need to tune all these values once the
logic is ready to be enabled.

Differential Revision: http://reviews.llvm.org/D9966

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239164 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/TargetTransformInfo.h
lib/Transforms/Scalar/LoopUnrollPass.cpp
test/Transforms/LoopUnroll/full-unroll-bad-geps.ll
test/Transforms/LoopUnroll/full-unroll-heuristics.ll

index 86bf154..ccd0a4d 100644 (file)
@@ -221,19 +221,21 @@ public:
 
   /// Parameters that control the generic loop unrolling transformation.
   struct UnrollingPreferences {
-    /// The cost threshold for the unrolled loop, compared to
-    /// CodeMetrics.NumInsts aggregated over all basic blocks in the loop body.
-    /// The unrolling factor is set such that the unrolled loop body does not
-    /// exceed this cost. Set this to UINT_MAX to disable the loop body cost
+    /// The cost threshold for the unrolled loop. Should be relative to the
+    /// getUserCost values returned by this API, and the expectation is that
+    /// the unrolled loop's instructions when run through that interface should
+    /// not exceed this cost. However, this is only an estimate. Also, specific
+    /// loops may be unrolled even with a cost above this threshold if deemed
+    /// profitable. Set this to UINT_MAX to disable the loop body cost
     /// restriction.
     unsigned Threshold;
-    /// If complete unrolling could help other optimizations (e.g. InstSimplify)
-    /// to remove N% of instructions, then we can go beyond unroll threshold.
-    /// This value set the minimal percent for allowing that.
-    unsigned MinPercentOfOptimized;
-    /// The absolute cost threshold. We won't go beyond this even if complete
-    /// unrolling could result in optimizing out 90% of instructions.
-    unsigned AbsoluteThreshold;
+    /// If complete unrolling will reduce the cost of the loop below its
+    /// expected dynamic cost while rolled by this percentage, apply a discount
+    /// (below) to its unrolled cost.
+    unsigned PercentDynamicCostSavedThreshold;
+    /// The discount applied to the unrolled cost when the *dynamic* cost
+    /// savings of unrolling exceed the \c PercentDynamicCostSavedThreshold.
+    unsigned DynamicCostSavingsDiscount;
     /// The cost threshold for the unrolled loop when optimizing for size (set
     /// to UINT_MAX to disable).
     unsigned OptSizeThreshold;
index ccafd10..d8ba964 100644 (file)
@@ -38,25 +38,25 @@ using namespace llvm;
 #define DEBUG_TYPE "loop-unroll"
 
 static cl::opt<unsigned>
-UnrollThreshold("unroll-threshold", cl::init(150), cl::Hidden,
-  cl::desc("The cut-off point for automatic loop unrolling"));
+    UnrollThreshold("unroll-threshold", cl::init(150), cl::Hidden,
+                    cl::desc("The baseline cost threshold for loop unrolling"));
+
+static cl::opt<unsigned> UnrollPercentDynamicCostSavedThreshold(
+    "unroll-percent-dynamic-cost-saved-threshold", cl::init(20), cl::Hidden,
+    cl::desc("The percentage of estimated dynamic cost which must be saved by "
+             "unrolling to allow unrolling up to the max threshold."));
+
+static cl::opt<unsigned> UnrollDynamicCostSavingsDiscount(
+    "unroll-dynamic-cost-savings-discount", cl::init(2000), cl::Hidden,
+    cl::desc("This is the amount discounted from the total unroll cost when "
+             "the unrolled form has a high dynamic cost savings (triggered by "
+             "the '-unroll-perecent-dynamic-cost-saved-threshold' flag)."));
 
 static cl::opt<unsigned> UnrollMaxIterationsCountToAnalyze(
     "unroll-max-iteration-count-to-analyze", cl::init(0), cl::Hidden,
     cl::desc("Don't allow loop unrolling to simulate more than this number of"
              "iterations when checking full unroll profitability"));
 
-static cl::opt<unsigned> UnrollMinPercentOfOptimized(
-    "unroll-percent-of-optimized-for-complete-unroll", cl::init(20), cl::Hidden,
-    cl::desc("If complete unrolling could trigger further optimizations, and, "
-             "by that, remove the given percent of instructions, perform the "
-             "complete unroll even if it's beyond the threshold"));
-
-static cl::opt<unsigned> UnrollAbsoluteThreshold(
-    "unroll-absolute-threshold", cl::init(2000), cl::Hidden,
-    cl::desc("Don't unroll if the unrolled size is bigger than this threshold,"
-             " even if we can remove big portion of instructions later."));
-
 static cl::opt<unsigned>
 UnrollCount("unroll-count", cl::init(0), cl::Hidden,
   cl::desc("Use this unroll count for all loops including those with "
@@ -82,16 +82,18 @@ namespace {
     static char ID; // Pass ID, replacement for typeid
     LoopUnroll(int T = -1, int C = -1, int P = -1, int R = -1) : LoopPass(ID) {
       CurrentThreshold = (T == -1) ? UnrollThreshold : unsigned(T);
-      CurrentAbsoluteThreshold = UnrollAbsoluteThreshold;
-      CurrentMinPercentOfOptimized = UnrollMinPercentOfOptimized;
+      CurrentPercentDynamicCostSavedThreshold =
+          UnrollPercentDynamicCostSavedThreshold;
+      CurrentDynamicCostSavingsDiscount = UnrollDynamicCostSavingsDiscount;
       CurrentCount = (C == -1) ? UnrollCount : unsigned(C);
       CurrentAllowPartial = (P == -1) ? UnrollAllowPartial : (bool)P;
       CurrentRuntime = (R == -1) ? UnrollRuntime : (bool)R;
 
       UserThreshold = (T != -1) || (UnrollThreshold.getNumOccurrences() > 0);
-      UserAbsoluteThreshold = (UnrollAbsoluteThreshold.getNumOccurrences() > 0);
-      UserPercentOfOptimized =
-          (UnrollMinPercentOfOptimized.getNumOccurrences() > 0);
+      UserPercentDynamicCostSavedThreshold =
+          (UnrollPercentDynamicCostSavedThreshold.getNumOccurrences() > 0);
+      UserDynamicCostSavingsDiscount =
+          (UnrollDynamicCostSavingsDiscount.getNumOccurrences() > 0);
       UserAllowPartial = (P != -1) ||
                          (UnrollAllowPartial.getNumOccurrences() > 0);
       UserRuntime = (R != -1) || (UnrollRuntime.getNumOccurrences() > 0);
@@ -115,18 +117,18 @@ namespace {
 
     unsigned CurrentCount;
     unsigned CurrentThreshold;
-    unsigned CurrentAbsoluteThreshold;
-    unsigned CurrentMinPercentOfOptimized;
-    bool     CurrentAllowPartial;
-    bool     CurrentRuntime;
-    bool     UserCount;            // CurrentCount is user-specified.
-    bool     UserThreshold;        // CurrentThreshold is user-specified.
-    bool UserAbsoluteThreshold;    // CurrentAbsoluteThreshold is
-                                   // user-specified.
-    bool UserPercentOfOptimized;   // CurrentMinPercentOfOptimized is
-                                   // user-specified.
-    bool     UserAllowPartial;     // CurrentAllowPartial is user-specified.
-    bool     UserRuntime;          // CurrentRuntime is user-specified.
+    unsigned CurrentPercentDynamicCostSavedThreshold;
+    unsigned CurrentDynamicCostSavingsDiscount;
+    bool CurrentAllowPartial;
+    bool CurrentRuntime;
+
+    // Flags for whether the 'current' settings are user-specified.
+    bool UserCount;
+    bool UserThreshold;
+    bool UserPercentDynamicCostSavedThreshold;
+    bool UserDynamicCostSavingsDiscount;
+    bool UserAllowPartial;
+    bool UserRuntime;
 
     bool runOnLoop(Loop *L, LPPassManager &LPM) override;
 
@@ -156,8 +158,9 @@ namespace {
     void getUnrollingPreferences(Loop *L, const TargetTransformInfo &TTI,
                                  TargetTransformInfo::UnrollingPreferences &UP) {
       UP.Threshold = CurrentThreshold;
-      UP.AbsoluteThreshold = CurrentAbsoluteThreshold;
-      UP.MinPercentOfOptimized = CurrentMinPercentOfOptimized;
+      UP.PercentDynamicCostSavedThreshold =
+          CurrentPercentDynamicCostSavedThreshold;
+      UP.DynamicCostSavingsDiscount = CurrentDynamicCostSavingsDiscount;
       UP.OptSizeThreshold = OptSizeUnrollThreshold;
       UP.PartialThreshold = CurrentThreshold;
       UP.PartialOptSizeThreshold = OptSizeUnrollThreshold;
@@ -186,8 +189,8 @@ namespace {
     void selectThresholds(const Loop *L, bool HasPragma,
                           const TargetTransformInfo::UnrollingPreferences &UP,
                           unsigned &Threshold, unsigned &PartialThreshold,
-                          unsigned &AbsoluteThreshold,
-                          unsigned &PercentOfOptimizedForCompleteUnroll) {
+                          unsigned &PercentDynamicCostSavedThreshold,
+                          unsigned &DynamicCostSavingsDiscount) {
       // Determine the current unrolling threshold.  While this is
       // normally set from UnrollThreshold, it is overridden to a
       // smaller value if the current function is marked as
@@ -195,11 +198,13 @@ namespace {
       // specified.
       Threshold = UserThreshold ? CurrentThreshold : UP.Threshold;
       PartialThreshold = UserThreshold ? CurrentThreshold : UP.PartialThreshold;
-      AbsoluteThreshold = UserAbsoluteThreshold ? CurrentAbsoluteThreshold
-                                                : UP.AbsoluteThreshold;
-      PercentOfOptimizedForCompleteUnroll = UserPercentOfOptimized
-                                                ? CurrentMinPercentOfOptimized
-                                                : UP.MinPercentOfOptimized;
+      PercentDynamicCostSavedThreshold =
+          UserPercentDynamicCostSavedThreshold
+              ? CurrentPercentDynamicCostSavedThreshold
+              : UP.PercentDynamicCostSavedThreshold;
+      DynamicCostSavingsDiscount = UserDynamicCostSavingsDiscount
+                                       ? CurrentDynamicCostSavingsDiscount
+                                       : UP.DynamicCostSavingsDiscount;
 
       if (!UserThreshold &&
           L->getHeader()->getParent()->hasFnAttribute(
@@ -220,9 +225,9 @@ namespace {
       }
     }
     bool canUnrollCompletely(Loop *L, unsigned Threshold,
-                             unsigned AbsoluteThreshold, uint64_t UnrolledSize,
-                             unsigned NumberOfOptimizedInstructions,
-                             unsigned PercentOfOptimizedForCompleteUnroll);
+                             unsigned PercentDynamicCostSavedThreshold,
+                             unsigned DynamicCostSavingsDiscount,
+                             unsigned UnrolledCost, unsigned RolledDynamicCost);
   };
 }
 
@@ -556,11 +561,12 @@ private:
 
 namespace {
 struct EstimatedUnrollCost {
-  /// \brief Count the number of optimized instructions.
-  unsigned NumberOfOptimizedInstructions;
+  /// \brief The estimated cost after unrolling.
+  unsigned UnrolledCost;
 
-  /// \brief Count the total number of instructions.
-  unsigned UnrolledLoopSize;
+  /// \brief The estimated dynamic cost of executing the instructions in the
+  /// rolled form.
+  unsigned RolledDynamicCost;
 };
 }
 
@@ -597,8 +603,15 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
   // each iteration. This cache is lazily self-populating.
   SCEVCache SC(*L, SE);
 
-  unsigned NumberOfOptimizedInstructions = 0;
-  unsigned UnrolledLoopSize = 0;
+  // The estimated cost of the unrolled form of the loop. We try to estimate
+  // this by simplifying as much as we can while computing the estimate.
+  unsigned UnrolledCost = 0;
+  // We also track the estimated dynamic (that is, actually executed) cost in
+  // the rolled form. This helps identify cases when the savings from unrolling
+  // aren't just exposing dead control flows, but actual reduced dynamic
+  // instructions due to the simplifications which we expect to occur after
+  // unrolling.
+  unsigned RolledDynamicCost = 0;
 
   // Simulate execution of each iteration of the loop counting instructions,
   // which would be simplified.
@@ -618,17 +631,20 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
       // it.  We don't change the actual IR, just count optimization
       // opportunities.
       for (Instruction &I : *BB) {
-        UnrolledLoopSize += TTI.getUserCost(&I);
+        unsigned InstCost = TTI.getUserCost(&I);
 
         // Visit the instruction to analyze its loop cost after unrolling,
-        // and if the visitor returns true, then we can optimize this
-        // instruction away.
-        if (Analyzer.visit(I))
-          NumberOfOptimizedInstructions += TTI.getUserCost(&I);
+        // and if the visitor returns false, include this instruction in the
+        // unrolled cost.
+        if (!Analyzer.visit(I))
+          UnrolledCost += InstCost;
+
+        // Also track this instructions expected cost when executing the rolled
+        // loop form.
+        RolledDynamicCost += InstCost;
 
         // If unrolled body turns out to be too big, bail out.
-        if (UnrolledLoopSize - NumberOfOptimizedInstructions >
-            MaxUnrolledLoopSize)
+        if (UnrolledCost > MaxUnrolledLoopSize)
           return None;
       }
 
@@ -640,10 +656,10 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, ScalarEvolution &SE,
 
     // If we found no optimization opportunities on the first iteration, we
     // won't find them on later ones too.
-    if (!NumberOfOptimizedInstructions)
+    if (UnrolledCost == RolledDynamicCost)
       return None;
   }
-  return {{NumberOfOptimizedInstructions, UnrolledLoopSize}};
+  return {{UnrolledCost, RolledDynamicCost}};
 }
 
 /// ApproximateLoopSize - Approximate the size of the loop.
@@ -749,46 +765,56 @@ static void SetLoopAlreadyUnrolled(Loop *L) {
   L->setLoopID(NewLoopID);
 }
 
-bool LoopUnroll::canUnrollCompletely(
-    Loop *L, unsigned Threshold, unsigned AbsoluteThreshold,
-    uint64_t UnrolledSize, unsigned NumberOfOptimizedInstructions,
-    unsigned PercentOfOptimizedForCompleteUnroll) {
+bool LoopUnroll::canUnrollCompletely(Loop *L, unsigned Threshold,
+                                     unsigned PercentDynamicCostSavedThreshold,
+                                     unsigned DynamicCostSavingsDiscount,
+                                     unsigned UnrolledCost,
+                                     unsigned RolledDynamicCost) {
 
   if (Threshold == NoThreshold) {
     DEBUG(dbgs() << "  Can fully unroll, because no threshold is set.\n");
     return true;
   }
 
-  if (UnrolledSize <= Threshold) {
-    DEBUG(dbgs() << "  Can fully unroll, because unrolled size: "
-                 << UnrolledSize << "<" << Threshold << "\n");
+  if (UnrolledCost <= Threshold) {
+    DEBUG(dbgs() << "  Can fully unroll, because unrolled cost: "
+                 << UnrolledCost << "<" << Threshold << "\n");
     return true;
   }
 
-  assert(UnrolledSize && "UnrolledSize can't be 0 at this point.");
-  unsigned PercentOfOptimizedInstructions =
-      (uint64_t)NumberOfOptimizedInstructions * 100ull / UnrolledSize;
-
-  if (UnrolledSize <= AbsoluteThreshold &&
-      PercentOfOptimizedInstructions >= PercentOfOptimizedForCompleteUnroll) {
-    DEBUG(dbgs() << "  Can fully unroll, because unrolling will help removing "
-                 << PercentOfOptimizedInstructions
-                 << "% instructions (threshold: "
-                 << PercentOfOptimizedForCompleteUnroll << "%)\n");
-    DEBUG(dbgs() << "  Unrolled size (" << UnrolledSize
-                 << ") is less than the threshold (" << AbsoluteThreshold
-                 << ").\n");
+  assert(UnrolledCost && "UnrolledCost can't be 0 at this point.");
+  assert(RolledDynamicCost >= UnrolledCost &&
+         "Cannot have a higher unrolled cost than a rolled cost!");
+
+  // Compute the percentage of the dynamic cost in the rolled form that is
+  // saved when unrolled. If unrolling dramatically reduces the estimated
+  // dynamic cost of the loop, we use a higher threshold to allow more
+  // unrolling.
+  unsigned PercentDynamicCostSaved =
+      (uint64_t)(RolledDynamicCost - UnrolledCost) * 100ull / RolledDynamicCost;
+
+  if (PercentDynamicCostSaved >= PercentDynamicCostSavedThreshold &&
+      (int64_t)UnrolledCost - (int64_t)DynamicCostSavingsDiscount <=
+          (int64_t)Threshold) {
+    DEBUG(dbgs() << "  Can fully unroll, because unrolling will reduce the "
+                    "expected dynamic cost by " << PercentDynamicCostSaved
+                 << "% (threshold: " << PercentDynamicCostSavedThreshold
+                 << "%)\n"
+                 << "  and the unrolled cost (" << UnrolledCost
+                 << ") is less than the max threshold ("
+                 << DynamicCostSavingsDiscount << ").\n");
     return true;
   }
 
   DEBUG(dbgs() << "  Too large to fully unroll:\n");
-  DEBUG(dbgs() << "    Unrolled size: " << UnrolledSize << "\n");
-  DEBUG(dbgs() << "    Estimated number of optimized instructions: "
-               << NumberOfOptimizedInstructions << "\n");
-  DEBUG(dbgs() << "    Absolute threshold: " << AbsoluteThreshold << "\n");
-  DEBUG(dbgs() << "    Minimum percent of removed instructions: "
-               << PercentOfOptimizedForCompleteUnroll << "\n");
-  DEBUG(dbgs() << "    Threshold for small loops: " << Threshold << "\n");
+  DEBUG(dbgs() << "    Threshold: " << Threshold << "\n");
+  DEBUG(dbgs() << "    Max threshold: " << DynamicCostSavingsDiscount << "\n");
+  DEBUG(dbgs() << "    Percent cost saved threshold: "
+               << PercentDynamicCostSavedThreshold << "%\n");
+  DEBUG(dbgs() << "    Unrolled cost: " << UnrolledCost << "\n");
+  DEBUG(dbgs() << "    Rolled dynamic cost: " << RolledDynamicCost << "\n");
+  DEBUG(dbgs() << "    Percent cost saved: " << PercentDynamicCostSaved
+               << "\n");
   return false;
 }
 
@@ -899,9 +925,11 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
   }
 
   unsigned Threshold, PartialThreshold;
-  unsigned AbsoluteThreshold, PercentOfOptimizedForCompleteUnroll;
+  unsigned PercentDynamicCostSavedThreshold;
+  unsigned DynamicCostSavingsDiscount;
   selectThresholds(L, HasPragma, UP, Threshold, PartialThreshold,
-                   AbsoluteThreshold, PercentOfOptimizedForCompleteUnroll);
+                   PercentDynamicCostSavedThreshold,
+                   DynamicCostSavingsDiscount);
 
   // Given Count, TripCount and thresholds determine the type of
   // unrolling which is to be performed.
@@ -910,20 +938,18 @@ bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
   if (TripCount && Count == TripCount) {
     Unrolling = Partial;
     // If the loop is really small, we don't need to run an expensive analysis.
-    if (canUnrollCompletely(
-            L, Threshold, AbsoluteThreshold,
-            UnrolledSize, 0, 100)) {
+    if (canUnrollCompletely(L, Threshold, 100, DynamicCostSavingsDiscount,
+                            UnrolledSize, UnrolledSize)) {
       Unrolling = Full;
     } else {
       // The loop isn't that small, but we still can fully unroll it if that
       // helps to remove a significant number of instructions.
       // To check that, run additional analysis on the loop.
-      if (Optional<EstimatedUnrollCost> Cost =
-              analyzeLoopUnrollCost(L, TripCount, *SE, TTI, AbsoluteThreshold))
-        if (canUnrollCompletely(L, Threshold, AbsoluteThreshold,
-                                Cost->UnrolledLoopSize,
-                                Cost->NumberOfOptimizedInstructions,
-                                PercentOfOptimizedForCompleteUnroll)) {
+      if (Optional<EstimatedUnrollCost> Cost = analyzeLoopUnrollCost(
+              L, TripCount, *SE, TTI, Threshold + DynamicCostSavingsDiscount))
+        if (canUnrollCompletely(L, Threshold, PercentDynamicCostSavedThreshold,
+                                DynamicCostSavingsDiscount, Cost->UnrolledCost,
+                                Cost->RolledDynamicCost)) {
           Unrolling = Full;
         }
     }
index 4c99bc7..ac81452 100644 (file)
@@ -1,5 +1,5 @@
 ; Check that we don't crash on corner cases.
-; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=10  -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=20 -o /dev/null
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=10 -unroll-percent-dynamic-cost-saved-threshold=20 -o /dev/null
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @foo1() {
index 2dab2fb..904a65a 100644 (file)
@@ -1,8 +1,8 @@
 ; In this test we check how heuristics for complete unrolling work. We have
 ; three knobs:
 ;  1) -unroll-threshold
-;  2) -unroll-absolute-threshold and
-;  3) -unroll-percent-of-optimized-for-complete-unroll
+;  3) -unroll-percent-dynamic-cost-saved-threshold and
+;  2) -unroll-dynamic-cost-savings-discount
 ;
 ; They control loop-unrolling according to the following rules:
 ;  * If size of unrolled loop exceeds the absoulte threshold, we don't unroll
 ; optimizations to remove ~55% of the instructions, the loop body size is 9,
 ; and unrolled size is 65.
 
-; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=10  -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=20 | FileCheck %s -check-prefix=TEST1
-; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=100 -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=20 | FileCheck %s -check-prefix=TEST2
-; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=100 -unroll-threshold=10  -unroll-percent-of-optimized-for-complete-unroll=80 | FileCheck %s -check-prefix=TEST3
-; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-absolute-threshold=100 -unroll-threshold=100 -unroll-percent-of-optimized-for-complete-unroll=80 | FileCheck %s -check-prefix=TEST4
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=10  -unroll-percent-dynamic-cost-saved-threshold=20 -unroll-dynamic-cost-savings-discount=0 | FileCheck %s -check-prefix=TEST1
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=10  -unroll-percent-dynamic-cost-saved-threshold=20 -unroll-dynamic-cost-savings-discount=90 | FileCheck %s -check-prefix=TEST2
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=10  -unroll-percent-dynamic-cost-saved-threshold=80 -unroll-dynamic-cost-savings-discount=90 | FileCheck %s -check-prefix=TEST3
+; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=1000 -unroll-threshold=100 -unroll-percent-dynamic-cost-saved-threshold=80 -unroll-dynamic-cost-savings-discount=0 | FileCheck %s -check-prefix=TEST4
 
 ; If the absolute threshold is too low, or if we can't optimize away requested
 ; percent of instructions, we shouldn't unroll: