[NFC] factor out unrolling decision logic

[Ali-Sed]

Summary

Decoupling the unrolling logic into three different functions. The shouldPragmaUnroll() covers the 1st and 2nd priorities of the previous code, the shouldFullUnroll() covers the 3rd, and the shouldPartialUnroll() covers the 5th. The output of each function, Optional<unsigned>, could be a value for UP.Count, which means unrolling factor has been set, or None, which means decision hasn't been made yet and should try the next priority.

[Ali-Sed]

[WIP][NFC] factor out unrolling decision logic

[mtrofin]

Thanks for fixing the commits! Please don't forget to add a commit message, both in git (i.e. git --amend and add a message), and then copy it in the summary here.

Like discussed offline, I think we should explore next splitting the logic of shouldUnroll into its constituent sub-pieces, i.e. shouldFullyUnroll, shouldPartiallyUnroll, etc; that will simplify their interface - the output of one of these can be an Optional<unsigned>, where the unsigned is the decided trip count (and None means 'no' such unrolling)

But maybe we can do that in a next patch - @jdoerfert , WDYT?

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

1075

remove the commented line altogether, also the free space.

[Ali-Sed]

[WIP][NFC]Seperating setting UP.count from other side parameters

[jdoerfert]

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

895

Use a struct with a name, not a pair of bools. It is much harder to determine what the bools mean this way, if you return an object of type struct SomeGoodName { bool InfoA; bool InfoB; } it is clear what the bools mean.
Same in other places.

1012

We have duplication here. Can you query this once and put everything into a "info struct" and then pass that to all the functions here.

Make the functions static if you can.

[Ali-Sed]

[WIP][NFC] Cleaning the params of functions --draft

[Ali-Sed]

[WIP][NFC] Changing bool, as the return arg of unrolling logics, to optional<unsigned>

[mtrofin]

Some nits, but lgtm assuming nits are fixed, tests pass, and also the message of this review is updated (e.g. remove WIP, and add a description for the change)

Wait for @jdoerfert if he has more feedback, too.

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

810

return None; (same below)

934

Up.Count = *UnrollFactor. The check above ensures the dereference succeeds.

985

same as above - *UnrollFactor

1017

same as above - *UnrollFactor

[Ali-Sed]

[NFC] Decoupling the unrolling logic into three different functions. The shouldPragmaUnroll() covers the 1st and 2nd priorities of the previous code, the shouldFullUnroll() covers the 3rd, and the shouldPartialUnroll() covers the 5th. The output of each function, Optional<unsigned>, could be a value for UP.Count, which means unrolling factor has been set, or None, which means decision hasn't been made yet and should try the next priority.

[Ali-Sed]

[NFC] Decoupling the unrolling logic
Decoupling the unrolling logic into three different functions. The shouldPragmaUnroll() covers the 1st and 2nd priorities of the previous code, the shouldFullUnroll() covers the 3rd, and the shouldPartialUnroll() covers the 5th. The output of each function, Optional<unsigned>, could be a value for UP.Count, which means unrolling factor has been set, or None, which means decision hasn't been made yet and should try the next priority.

[mtrofin]

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

323

Nit: bool and unsigned don't get initialized, so to avoid nasty nondeterministic bugs, easiest to assign them on declaration, here, i.e. bool UserUnrollCount = false; unsigned PragmaCount = 0; etc. This improves also maintainability, because it's *much* easier for folks working with the code to follow the same pattern if they add more fields, and also figure out where the object is initialized (less reading required, basically)

766

do static_cast<uint64_t>(same stuff)

same below

894

delete this line, it's spurious

903

One thing to consider: if PragmaInfo are just carriers of those fields, and (currently) they are meant to be set once, I'd make the code even more maintainable if:

• the fields were const
• the struct had a ctor where you pass them and set them

that way, it's very clear that a PragmaInfo object has intentionally initialized fields, and also that they can't ever be changed.

937

why binary or? i.e. did you mean || ?

964

remove spurious line

999

remove spurious line

1037–1038

line

1040

line

[jdoerfert]

LG for the high level change, @mtrofin mentioned changes then it's good to go.

[Ali-Sed]

[NFC] fixing NITs

[Ali-Sed]

[NFC] mergin temp branch and main

[Ali-Sed]

[NFC] Fixing conflict issue

[Ali-Sed]

[NFC] fixing merge conflicts

[GMNGeoffrey]

By including <optional> this makes LLVM require C++17, which it shouldn't: https://llvm.org/docs/CodingStandards.html#c-standard-versions

[Ali-Sed]

[NFC] Fixing dependency to C++17

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

struct EstimatedUnrollCost {
   /// The estimated cost after unrolling.
   unsigned UnrolledCost;
 
   /// The estimated dynamic cost of executing the instructions in the
   /// rolled form.
   unsigned RolledDynamicCost;
 };
 
+struct PragmaInfo {
+  PragmaInfo(bool UUC, bool PFU, unsigned PC, bool PEU)
+      : UserUnrollCount(UUC), PragmaFullUnroll(PFU), PragmaCount(PC),
+        PragmaEnableUnroll(PEU) {}
+  const bool UserUnrollCount;
+  const bool PragmaFullUnroll;
+  const unsigned PragmaCount;
+  const bool PragmaEnableUnroll;
+};
+
 } // end anonymous namespace
 
 /// Figure out if the loop is worth full unrolling.
 ///
 /// Complete loop unrolling can make some loads constant, and we need to know
 /// if that would expose any further optimization opportunities.  This routine
 /// estimates this optimization.  It computes cost of unrolled loop
 /// (UnrolledCost) and dynamic cost of the original loop (RolledDynamicCost). By

 class UnrollCostEstimator {
   const unsigned LoopSize;
 
 public:
   UnrollCostEstimator(Loop &L, unsigned LoopSize) : LoopSize(LoopSize) {}
 
   // Returns loop size estimation for unrolled loop, given the unrolling
   // configuration specified by UP.
-  uint64_t getUnrolledLoopSize(TargetTransformInfo::UnrollingPreferences &UP) {
+  uint64_t
+  getUnrolledLoopSize(const TargetTransformInfo::UnrollingPreferences &UP,
+                      const unsigned CountOverwrite = 0) const {
     assert(LoopSize >= UP.BEInsns &&
            "LoopSize should not be less than BEInsns!");
-    return (uint64_t)(LoopSize - UP.BEInsns) * UP.Count + UP.BEInsns;
+    if (CountOverwrite)
+      return static_cast<uint64_t>(LoopSize - UP.BEInsns) * CountOverwrite +
+             UP.BEInsns;
+    else
+      return static_cast<uint64_t>(LoopSize - UP.BEInsns) * UP.Count +
+             UP.BEInsns;
   }
 };
 
+static Optional<unsigned>
+shouldPragmaUnroll(Loop *L, const PragmaInfo &PInfo,
+                   const unsigned TripMultiple, const unsigned TripCount,
+                   const UnrollCostEstimator UCE,
+                   const TargetTransformInfo::UnrollingPreferences &UP) {
+
+  // Using unroll pragma
+  // 1st priority is unroll count set by "unroll-count" option.
+
+  if (PInfo.UserUnrollCount) {
+    if (UP.AllowRemainder &&
+        UCE.getUnrolledLoopSize(UP, (unsigned)UnrollCount) < UP.Threshold)
+      return (unsigned)UnrollCount;
+  }
+
+  // 2nd priority is unroll count set by pragma.
+  if (PInfo.PragmaCount > 0) {
+    if ((UP.AllowRemainder || (TripMultiple % PInfo.PragmaCount == 0)) &&
+        UCE.getUnrolledLoopSize(UP, PInfo.PragmaCount) < PragmaUnrollThreshold)
+      return PInfo.PragmaCount;
+  }
+
+  if (PInfo.PragmaFullUnroll && TripCount != 0) {
+    if (UCE.getUnrolledLoopSize(UP, TripCount) < PragmaUnrollThreshold)
+      return TripCount;
+  }
+  // if didn't return until here, should continue to other priorties
+  return None;
+}
+
+static Optional<unsigned> shouldFullUnroll(
+    Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT,
+    ScalarEvolution &SE, const SmallPtrSetImpl<const Value *> &EphValues,
+    const unsigned FullUnrollTripCount, const UnrollCostEstimator UCE,
+    const TargetTransformInfo::UnrollingPreferences &UP) {
+
+  if (FullUnrollTripCount && FullUnrollTripCount <= UP.FullUnrollMaxCount) {
+    // When computing the unrolled size, note that BEInsns are not replicated
+    // like the rest of the loop body.
+    if (UCE.getUnrolledLoopSize(UP) < UP.Threshold) {
+      return FullUnrollTripCount;
+
+    } 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, FullUnrollTripCount, DT, SE, EphValues, TTI,
+              UP.Threshold * UP.MaxPercentThresholdBoost / 100,
+              UP.MaxIterationsCountToAnalyze)) {
+        unsigned Boost =
+            getFullUnrollBoostingFactor(*Cost, UP.MaxPercentThresholdBoost);
+        if (Cost->UnrolledCost < UP.Threshold * Boost / 100) {
+          return FullUnrollTripCount;
+        }
+      }
+    }
+  }
+  return None;
+}
+
+static Optional<unsigned>
+shouldPartialUnroll(const unsigned LoopSize, const unsigned TripCount,
+                    const UnrollCostEstimator UCE,
+                    const TargetTransformInfo::UnrollingPreferences &UP) {
+
+  unsigned count = UP.Count;
+  if (TripCount) {
+    if (!UP.Partial) {
+      LLVM_DEBUG(dbgs() << "  will not try to unroll partially because "
+                        << "-unroll-allow-partial not given\n");
+      count = 0;
+      return count;
+    }
+    if (count == 0)
+      count = TripCount;
+    if (UP.PartialThreshold != NoThreshold) {
+      // Reduce unroll count to be modulo of TripCount for partial unrolling.
+      if (UCE.getUnrolledLoopSize(UP, count) > UP.PartialThreshold)
+        count = (std::max(UP.PartialThreshold, UP.BEInsns + 1) - UP.BEInsns) /
+                (LoopSize - UP.BEInsns);
+      if (count > UP.MaxCount)
+        count = UP.MaxCount;
+      while (count != 0 && TripCount % count != 0)
+        count--;
+      if (UP.AllowRemainder && count <= 1) {
+        // If there is no Count that is modulo of TripCount, set Count to
+        // largest power-of-two factor that satisfies the threshold limit.
+        // As we'll create fixup loop, do the type of unrolling only if
+        // remainder loop is allowed.
+        count = UP.DefaultUnrollRuntimeCount;
+        while (count != 0 &&
+               UCE.getUnrolledLoopSize(UP, count) > UP.PartialThreshold)
+          count >>= 1;
+      }
+      if (count < 2) {
+        count = 0;
+      }
+    } else {
+      count = TripCount;
+    }
+    if (count > UP.MaxCount)
+      count = UP.MaxCount;
+
+    LLVM_DEBUG(dbgs() << "  partially unrolling with count: " << count << "\n");
+
+    return count;
+  }
+
+  // if didn't return until here, should continue to other priorties
+  return None;
+}
 // Returns true if unroll count was set explicitly.
 // Calculates unroll count and writes it to UP.Count.
 // Unless IgnoreUser is true, will also use metadata and command-line options
 // that are specific to to the LoopUnroll pass (which, for instance, are
 // irrelevant for the LoopUnrollAndJam pass).
 // FIXME: This function is used by LoopUnroll and LoopUnrollAndJam, but consumes
 // many LoopUnroll-specific options. The shared functionality should be
 // refactored into it own function.
 bool llvm::computeUnrollCount(
     Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT, LoopInfo *LI,
     ScalarEvolution &SE, const SmallPtrSetImpl<const Value *> &EphValues,
     OptimizationRemarkEmitter *ORE, unsigned TripCount, unsigned MaxTripCount,
     bool MaxOrZero, unsigned TripMultiple, unsigned LoopSize,
     TargetTransformInfo::UnrollingPreferences &UP,
     TargetTransformInfo::PeelingPreferences &PP, bool &UseUpperBound) {
 
   UnrollCostEstimator UCE(*L, LoopSize);
+  Optional<unsigned> UnrollFactor;
+
+  const bool UserUnrollCount = UnrollCount.getNumOccurrences() > 0;
+  const bool PragmaFullUnroll = hasUnrollFullPragma(L);
+  const unsigned PragmaCount = unrollCountPragmaValue(L);
+  const bool PragmaEnableUnroll = hasUnrollEnablePragma(L);
+
+  const bool ExplicitUnroll = PragmaCount > 0 || PragmaFullUnroll ||
+                              PragmaEnableUnroll || UserUnrollCount;
 
+  PragmaInfo PInfo(UserUnrollCount, PragmaFullUnroll, PragmaCount,
+                   PragmaEnableUnroll);
   // Use an explicit peel count that has been specified for testing. In this
   // case it's not permitted to also specify an explicit unroll count.
   if (PP.PeelCount) {
     if (UnrollCount.getNumOccurrences() > 0) {
       report_fatal_error("Cannot specify both explicit peel count and "
                          "explicit unroll count");
     }
     UP.Count = 1;
     UP.Runtime = false;
     return true;
   }
-
   // Check for explicit Count.
   // 1st priority is unroll count set by "unroll-count" option.
-  bool UserUnrollCount = UnrollCount.getNumOccurrences() > 0;
-  if (UserUnrollCount) {
-    UP.Count = UnrollCount;
-    UP.AllowExpensiveTripCount = true;
-    UP.Force = true;
-    if (UP.AllowRemainder && UCE.getUnrolledLoopSize(UP) < UP.Threshold)
-      return true;
-  }
-
   // 2nd priority is unroll count set by pragma.
-  unsigned PragmaCount = unrollCountPragmaValue(L);
-  if (PragmaCount > 0) {
-    UP.Count = PragmaCount;
-    UP.Runtime = true;
+  UnrollFactor = shouldPragmaUnroll(L, PInfo, TripMultiple, TripCount, UCE, UP);
+
+  if (UnrollFactor) {
+    UP.Count = *UnrollFactor;
+
+    if (UserUnrollCount || (PragmaCount > 0)) {
       UP.AllowExpensiveTripCount = true;
       UP.Force = true;
-    if ((UP.AllowRemainder || (TripMultiple % PragmaCount == 0)) &&
-        UCE.getUnrolledLoopSize(UP) < PragmaUnrollThreshold)
-      return true;
     }
-  bool PragmaFullUnroll = hasUnrollFullPragma(L);
-  if (PragmaFullUnroll && TripCount != 0) {
-    UP.Count = TripCount;
-    if (UCE.getUnrolledLoopSize(UP) < PragmaUnrollThreshold)
-      return false;
-  }
-
-  bool PragmaEnableUnroll = hasUnrollEnablePragma(L);
-  bool ExplicitUnroll = PragmaCount > 0 || PragmaFullUnroll ||
-                        PragmaEnableUnroll || UserUnrollCount;
-
+    UP.Runtime |= (PragmaCount > 0);
+    return ExplicitUnroll;
+  } else {
     if (ExplicitUnroll && TripCount != 0) {
       // If the loop has an unrolling pragma, we want to be more aggressive with
       // unrolling limits. Set thresholds to at least the PragmaUnrollThreshold
       // value which is larger than the default limits.
       UP.Threshold = std::max<unsigned>(UP.Threshold, PragmaUnrollThreshold);
       UP.PartialThreshold =
           std::max<unsigned>(UP.PartialThreshold, PragmaUnrollThreshold);
     }
+  }
 
   // 3rd priority is full unroll count.
   // Full unroll makes sense only when TripCount or its upper bound could be
   // statically calculated.
   // Also we need to check if we exceed FullUnrollMaxCount.
 
   // We can unroll by the upper bound amount if it's generally allowed or if
   // we know that the loop is executed either the upper bound or zero times.
   // (MaxOrZero unrolling keeps only the first loop test, so the number of
   // loop tests remains the same compared to the non-unrolled version, whereas
   // the generic upper bound unrolling keeps all but the last loop test so the
   // number of loop tests goes up which may end up being worse on targets with
   // constrained branch predictor resources so is controlled by an option.)
   // In addition we only unroll small upper bounds.
   unsigned FullUnrollMaxTripCount = MaxTripCount;
   if (!(UP.UpperBound || MaxOrZero) ||
       FullUnrollMaxTripCount > UnrollMaxUpperBound)
     FullUnrollMaxTripCount = 0;
 
   // UnrollByMaxCount and ExactTripCount cannot both be non zero since we only
   // compute the former when the latter is zero.
   unsigned ExactTripCount = TripCount;
   assert((ExactTripCount == 0 || FullUnrollMaxTripCount == 0) &&
          "ExtractTripCount and UnrollByMaxCount cannot both be non zero.");
 
   unsigned FullUnrollTripCount =
       ExactTripCount ? ExactTripCount : FullUnrollMaxTripCount;
   UP.Count = FullUnrollTripCount;
-  if (FullUnrollTripCount && FullUnrollTripCount <= UP.FullUnrollMaxCount) {
-    // When computing the unrolled size, note that BEInsns are not replicated
-    // like the rest of the loop body.
-    if (UCE.getUnrolledLoopSize(UP) < UP.Threshold) {
-      UseUpperBound = (FullUnrollMaxTripCount == FullUnrollTripCount);
-      return ExplicitUnroll;
-    } 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, FullUnrollTripCount, DT, SE, EphValues, TTI,
-              UP.Threshold * UP.MaxPercentThresholdBoost / 100,
-              UP.MaxIterationsCountToAnalyze)) {
-        unsigned Boost =
-            getFullUnrollBoostingFactor(*Cost, UP.MaxPercentThresholdBoost);
-        if (Cost->UnrolledCost < UP.Threshold * Boost / 100) {
-          UseUpperBound = (FullUnrollMaxTripCount == FullUnrollTripCount);
-          return ExplicitUnroll;
-        }
-      }
-    }
+
+  UnrollFactor =
+      shouldFullUnroll(L, TTI, DT, SE, EphValues, FullUnrollTripCount, UCE, UP);
+
+  // if shouldFullUnroll can do the unrolling, some side parameteres should be
+  // set
+  if (UnrollFactor) {
+    UP.Count = *UnrollFactor;
+    TripCount = FullUnrollTripCount;
+    TripMultiple = UP.UpperBound ? 1 : TripMultiple;
+    UP.Count = FullUnrollTripCount;
   }
 
   // 4th priority is loop peeling.
   computePeelCount(L, LoopSize, PP, TripCount, SE, UP.Threshold);
   if (PP.PeelCount) {
     UP.Runtime = false;
     UP.Count = 1;
     return ExplicitUnroll;
   }
 
+  // Before starting partial unrolling, set up.partial to true,
+  // if user explicitly asked  for unrolling
+  if (TripCount)
+    UP.Partial |= ExplicitUnroll;
+
   // 5th priority is partial unrolling.
   // Try partial unroll only when TripCount could be statically calculated.
-  if (TripCount) {
-    UP.Partial |= ExplicitUnroll;
-    if (!UP.Partial) {
-      LLVM_DEBUG(dbgs() << "  will not try to unroll partially because "
-                        << "-unroll-allow-partial not given\n");
-      UP.Count = 0;
-      return false;
-    }
-    if (UP.Count == 0)
-      UP.Count = TripCount;
+  UnrollFactor = shouldPartialUnroll(LoopSize, TripCount, UCE, UP);
+
+  if (UnrollFactor) {
+    UP.Count = *UnrollFactor;
+
+    if ((PragmaFullUnroll || PragmaEnableUnroll) && TripCount &&
+        UP.Count != TripCount)
+      ORE->emit([&]() {
+        return OptimizationRemarkMissed(DEBUG_TYPE,
+                                        "FullUnrollAsDirectedTooLarge",
+                                        L->getStartLoc(), L->getHeader())
+               << "Unable to fully unroll loop as directed by unroll pragma "
+                  "because "
+                  "unrolled size is too large.";
+      });
+
     if (UP.PartialThreshold != NoThreshold) {
-      // Reduce unroll count to be modulo of TripCount for partial unrolling.
-      if (UCE.getUnrolledLoopSize(UP) > UP.PartialThreshold)
-        UP.Count =
-            (std::max(UP.PartialThreshold, UP.BEInsns + 1) - UP.BEInsns) /
-            (LoopSize - UP.BEInsns);
-      if (UP.Count > UP.MaxCount)
-        UP.Count = UP.MaxCount;
-      while (UP.Count != 0 && TripCount % UP.Count != 0)
-        UP.Count--;
-      if (UP.AllowRemainder && UP.Count <= 1) {
-        // If there is no Count that is modulo of TripCount, set Count to
-        // largest power-of-two factor that satisfies the threshold limit.
-        // As we'll create fixup loop, do the type of unrolling only if
-        // remainder loop is allowed.
-        UP.Count = UP.DefaultUnrollRuntimeCount;
-        while (UP.Count != 0 &&
-               UCE.getUnrolledLoopSize(UP) > UP.PartialThreshold)
-          UP.Count >>= 1;
-      }
-      if (UP.Count < 2) {
+      if (UP.Count == 0) {
         if (PragmaEnableUnroll)
           ORE->emit([&]() {
             return OptimizationRemarkMissed(DEBUG_TYPE,
                                             "UnrollAsDirectedTooLarge",
                                             L->getStartLoc(), L->getHeader())
                    << "Unable to unroll loop as directed by unroll(enable) "
                       "pragma "
                       "because unrolled size is too large.";
           });
-        UP.Count = 0;
       }
-    } else {
-      UP.Count = TripCount;
     }
-    if (UP.Count > UP.MaxCount)
-      UP.Count = UP.MaxCount;
-    if ((PragmaFullUnroll || PragmaEnableUnroll) && TripCount &&
-        UP.Count != TripCount)
-      ORE->emit([&]() {
-        return OptimizationRemarkMissed(DEBUG_TYPE,
-                                        "FullUnrollAsDirectedTooLarge",
-                                        L->getStartLoc(), L->getHeader())
-               << "Unable to fully unroll loop as directed by unroll pragma "
-                  "because "
-                  "unrolled size is too large.";
-      });
-    LLVM_DEBUG(dbgs() << "  partially unrolling with count: " << UP.Count
-                      << "\n");
     return ExplicitUnroll;
   }
   assert(TripCount == 0 &&
          "All cases when TripCount is constant should be covered here.");
   if (PragmaFullUnroll)
     ORE->emit([&]() {
       return OptimizationRemarkMissed(
                  DEBUG_TYPE, "CantFullUnrollAsDirectedRuntimeTripCount",
                  L->getStartLoc(), L->getHeader())
              << "Unable to fully unroll loop as directed by unroll(full) "
                 "pragma "
bool llvm::computeUnrollCount(
   if (L->getHeader()->getParent()->hasProfileData()) {
     if (auto ProfileTripCount = getLoopEstimatedTripCount(L)) {
       if (*ProfileTripCount < FlatLoopTripCountThreshold)
         return false;
       else
         UP.AllowExpensiveTripCount = true;
     }
   }
-
-  // Reduce count based on the type of unrolling and the threshold values.
   UP.Runtime |= PragmaEnableUnroll || PragmaCount > 0 || UserUnrollCount;
   if (!UP.Runtime) {
     LLVM_DEBUG(
         dbgs() << "  will not try to unroll loop with runtime trip count "
                << "-unroll-runtime not given\n");
     UP.Count = 0;
     return false;
   }
   if (UP.Count == 0)
     UP.Count = UP.DefaultUnrollRuntimeCount;
LLVM_DEBUG(
                   "specific or because the loop contains a convergent "
                   "instruction), so unroll count must divide the trip "
                   "multiple, "
                << TripMultiple << ".  Reducing unroll count from " << OrigCount
                << " to " << UP.Count << ".\n");
 
     using namespace ore;
 
-    if (PragmaCount > 0 && !UP.AllowRemainder)
+    if (unrollCountPragmaValue(L) > 0 && !UP.AllowRemainder)
       ORE->emit([&]() {
         return OptimizationRemarkMissed(DEBUG_TYPE,
                                         "DifferentUnrollCountFromDirected",
                                         L->getStartLoc(), L->getHeader())
                << "Unable to unroll loop the number of times directed by "
                   "unroll_count pragma because remainder loop is restricted "
                   "(that could architecture specific or because the loop "
                   "contains a convergent instruction) and so must have an "