// counts of loops easily.
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "loop-unroll"
-#include "llvm/IntrinsicInst.h"
#include "llvm/Transforms/Scalar.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/CodeMetrics.h"
+#include "llvm/Analysis/FunctionTargetTransformInfo.h"
#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Analysis/InlineCost.h"
#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Metadata.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
+#define DEBUG_TYPE "loop-unroll"
+
static cl::opt<unsigned>
-UnrollThreshold("unroll-threshold", cl::init(0), cl::Hidden,
+UnrollThreshold("unroll-threshold", cl::init(150), cl::Hidden,
cl::desc("The cut-off point for automatic loop unrolling"));
static cl::opt<unsigned>
UnrollCount("unroll-count", cl::init(0), cl::Hidden,
- cl::desc("Use this unroll count for all loops, for testing purposes"));
+ cl::desc("Use this unroll count for all loops including those with "
+ "unroll_count pragma values, for testing purposes"));
static cl::opt<bool>
UnrollAllowPartial("unroll-allow-partial", cl::init(false), cl::Hidden,
cl::desc("Allows loops to be partially unrolled until "
"-unroll-threshold loop size is reached."));
+static cl::opt<bool>
+UnrollRuntime("unroll-runtime", cl::ZeroOrMore, cl::init(false), cl::Hidden,
+ cl::desc("Unroll loops with run-time trip counts"));
+
+static cl::opt<unsigned>
+PragmaUnrollThreshold("pragma-unroll-threshold", cl::init(16 * 1024), cl::Hidden,
+ cl::desc("Unrolled size limit for loops with an unroll(full) or "
+ "unroll_count pragma."));
+
namespace {
class LoopUnroll : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
- LoopUnroll() : LoopPass(ID) {}
+ LoopUnroll(int T = -1, int C = -1, int P = -1, int R = -1) : LoopPass(ID) {
+ CurrentThreshold = (T == -1) ? UnrollThreshold : unsigned(T);
+ CurrentCount = (C == -1) ? UnrollCount : unsigned(C);
+ CurrentAllowPartial = (P == -1) ? UnrollAllowPartial : (bool)P;
+ CurrentRuntime = (R == -1) ? UnrollRuntime : (bool)R;
+
+ UserThreshold = (T != -1) || (UnrollThreshold.getNumOccurrences() > 0);
+ UserAllowPartial = (P != -1) ||
+ (UnrollAllowPartial.getNumOccurrences() > 0);
+ UserRuntime = (R != -1) || (UnrollRuntime.getNumOccurrences() > 0);
+ UserCount = (C != -1) || (UnrollCount.getNumOccurrences() > 0);
+
+ initializeLoopUnrollPass(*PassRegistry::getPassRegistry());
+ }
/// A magic value for use with the Threshold parameter to indicate
/// that the loop unroll should be performed regardless of how much
/// code expansion would result.
static const unsigned NoThreshold = UINT_MAX;
-
+
// Threshold to use when optsize is specified (and there is no
// explicit -unroll-threshold).
static const unsigned OptSizeUnrollThreshold = 50;
-
+
+ // Default unroll count for loops with run-time trip count if
+ // -unroll-count is not set
+ static const unsigned UnrollRuntimeCount = 8;
+
+ unsigned CurrentCount;
unsigned CurrentThreshold;
+ bool CurrentAllowPartial;
+ bool CurrentRuntime;
+ bool UserCount; // CurrentCount is user-specified.
+ bool UserThreshold; // CurrentThreshold is user-specified.
+ bool UserAllowPartial; // CurrentAllowPartial is user-specified.
+ bool UserRuntime; // CurrentRuntime is user-specified.
- bool runOnLoop(Loop *L, LPPassManager &LPM);
+ bool runOnLoop(Loop *L, LPPassManager &LPM) override;
/// This transformation requires natural loop information & requires that
/// loop preheaders be inserted into the CFG...
///
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LoopInfo>();
- AU.addPreserved<LoopInfo>();
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<LoopInfoWrapperPass>();
+ AU.addPreserved<LoopInfoWrapperPass>();
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
+ AU.addRequired<ScalarEvolution>();
AU.addPreserved<ScalarEvolution>();
+ AU.addRequired<TargetTransformInfoWrapperPass>();
+ AU.addRequired<FunctionTargetTransformInfo>();
// FIXME: Loop unroll requires LCSSA. And LCSSA requires dom info.
// If loop unroll does not preserve dom info then LCSSA pass on next
// loop will receive invalid dom info.
// For now, recreate dom info, if loop is unrolled.
- AU.addPreserved<DominatorTree>();
+ AU.addPreserved<DominatorTreeWrapperPass>();
+ }
+
+ // Fill in the UnrollingPreferences parameter with values from the
+ // TargetTransformationInfo.
+ void getUnrollingPreferences(Loop *L, const FunctionTargetTransformInfo &FTTI,
+ TargetTransformInfo::UnrollingPreferences &UP) {
+ UP.Threshold = CurrentThreshold;
+ UP.OptSizeThreshold = OptSizeUnrollThreshold;
+ UP.PartialThreshold = CurrentThreshold;
+ UP.PartialOptSizeThreshold = OptSizeUnrollThreshold;
+ UP.Count = CurrentCount;
+ UP.MaxCount = UINT_MAX;
+ UP.Partial = CurrentAllowPartial;
+ UP.Runtime = CurrentRuntime;
+ FTTI.getUnrollingPreferences(L, UP);
+ }
+
+ // Select and return an unroll count based on parameters from
+ // user, unroll preferences, unroll pragmas, or a heuristic.
+ // SetExplicitly is set to true if the unroll count is is set by
+ // the user or a pragma rather than selected heuristically.
+ unsigned
+ selectUnrollCount(const Loop *L, unsigned TripCount, bool PragmaFullUnroll,
+ unsigned PragmaCount,
+ const TargetTransformInfo::UnrollingPreferences &UP,
+ bool &SetExplicitly);
+
+ // Select threshold values used to limit unrolling based on a
+ // total unrolled size. Parameters Threshold and PartialThreshold
+ // are set to the maximum unrolled size for fully and partially
+ // unrolled loops respectively.
+ void selectThresholds(const Loop *L, bool HasPragma,
+ const TargetTransformInfo::UnrollingPreferences &UP,
+ unsigned &Threshold, unsigned &PartialThreshold) {
+ // 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
+ // optimize-for-size, and the unroll threshold was not user
+ // specified.
+ Threshold = UserThreshold ? CurrentThreshold : UP.Threshold;
+ PartialThreshold = UserThreshold ? CurrentThreshold : UP.PartialThreshold;
+ if (!UserThreshold &&
+ L->getHeader()->getParent()->getAttributes().
+ hasAttribute(AttributeSet::FunctionIndex,
+ Attribute::OptimizeForSize)) {
+ Threshold = UP.OptSizeThreshold;
+ PartialThreshold = UP.PartialOptSizeThreshold;
+ }
+ if (HasPragma) {
+ // If the loop has an unrolling pragma, we want to be more
+ // aggressive with unrolling limits. Set thresholds to at
+ // least the PragmaTheshold value which is larger than the
+ // default limits.
+ if (Threshold != NoThreshold)
+ Threshold = std::max<unsigned>(Threshold, PragmaUnrollThreshold);
+ if (PartialThreshold != NoThreshold)
+ PartialThreshold =
+ std::max<unsigned>(PartialThreshold, PragmaUnrollThreshold);
+ }
}
};
}
char LoopUnroll::ID = 0;
-INITIALIZE_PASS(LoopUnroll, "loop-unroll", "Unroll loops", false, false);
+INITIALIZE_PASS_BEGIN(LoopUnroll, "loop-unroll", "Unroll loops", false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(FunctionTargetTransformInfo)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
+INITIALIZE_PASS_DEPENDENCY(LCSSA)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
+INITIALIZE_PASS_END(LoopUnroll, "loop-unroll", "Unroll loops", false, false)
+
+Pass *llvm::createLoopUnrollPass(int Threshold, int Count, int AllowPartial,
+ int Runtime) {
+ return new LoopUnroll(Threshold, Count, AllowPartial, Runtime);
+}
-Pass *llvm::createLoopUnrollPass() { return new LoopUnroll(); }
+Pass *llvm::createSimpleLoopUnrollPass() {
+ return llvm::createLoopUnrollPass(-1, -1, 0, 0);
+}
/// ApproximateLoopSize - Approximate the size of the loop.
-static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls) {
+static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
+ bool &NotDuplicatable,
+ const TargetTransformInfo &TTI,
+ AssumptionCache *AC) {
+ SmallPtrSet<const Value *, 32> EphValues;
+ CodeMetrics::collectEphemeralValues(L, AC, EphValues);
+
CodeMetrics Metrics;
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I)
- Metrics.analyzeBasicBlock(*I);
- NumCalls = Metrics.NumCalls;
-
+ Metrics.analyzeBasicBlock(*I, TTI, EphValues);
+ NumCalls = Metrics.NumInlineCandidates;
+ NotDuplicatable = Metrics.notDuplicatable;
+
unsigned LoopSize = Metrics.NumInsts;
-
- // If we can identify the induction variable, we know that it will become
- // constant when we unroll the loop, so factor that into our loop size
- // estimate.
- // FIXME: We have to divide by InlineConstants::InstrCost because the
- // measure returned by CountCodeReductionForConstant is not an instruction
- // count, but rather a weight as defined by InlineConstants. It would
- // probably be a good idea to standardize on a single weighting scheme by
- // pushing more of the logic for weighting into CodeMetrics.
- if (PHINode *IndVar = L->getCanonicalInductionVariable()) {
- unsigned SizeDecrease = Metrics.CountCodeReductionForConstant(IndVar);
- // NOTE: Because SizeDecrease is a fuzzy estimate, we don't want to allow
- // it to totally negate the cost of unrolling a loop.
- SizeDecrease = SizeDecrease > LoopSize / 2 ? LoopSize / 2 : SizeDecrease;
- }
-
+
// Don't allow an estimate of size zero. This would allows unrolling of loops
// with huge iteration counts, which is a compile time problem even if it's
- // not a problem for code quality.
- if (LoopSize == 0) LoopSize = 1;
-
+ // not a problem for code quality. Also, the code using this size may assume
+ // that each loop has at least three instructions (likely a conditional
+ // branch, a comparison feeding that branch, and some kind of loop increment
+ // feeding that comparison instruction).
+ LoopSize = std::max(LoopSize, 3u);
+
return LoopSize;
}
+// Returns the loop hint metadata node with the given name (for example,
+// "llvm.loop.unroll.count"). If no such metadata node exists, then nullptr is
+// returned.
+static const MDNode *GetUnrollMetadataForLoop(const Loop *L, StringRef Name) {
+ MDNode *LoopID = L->getLoopID();
+ if (!LoopID)
+ return nullptr;
+ return GetUnrollMetadata(LoopID, Name);
+}
+
+// Returns true if the loop has an unroll(full) pragma.
+static bool HasUnrollFullPragma(const Loop *L) {
+ return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.full");
+}
+
+// Returns true if the loop has an unroll(disable) pragma.
+static bool HasUnrollDisablePragma(const Loop *L) {
+ return GetUnrollMetadataForLoop(L, "llvm.loop.unroll.disable");
+}
+
+// If loop has an unroll_count pragma return the (necessarily
+// positive) value from the pragma. Otherwise return 0.
+static unsigned UnrollCountPragmaValue(const Loop *L) {
+ const MDNode *MD = GetUnrollMetadataForLoop(L, "llvm.loop.unroll.count");
+ if (MD) {
+ assert(MD->getNumOperands() == 2 &&
+ "Unroll count hint metadata should have two operands.");
+ unsigned Count =
+ mdconst::extract<ConstantInt>(MD->getOperand(1))->getZExtValue();
+ assert(Count >= 1 && "Unroll count must be positive.");
+ return Count;
+ }
+ return 0;
+}
+
+// Remove existing unroll metadata and add unroll disable metadata to
+// indicate the loop has already been unrolled. This prevents a loop
+// from being unrolled more than is directed by a pragma if the loop
+// unrolling pass is run more than once (which it generally is).
+static void SetLoopAlreadyUnrolled(Loop *L) {
+ MDNode *LoopID = L->getLoopID();
+ if (!LoopID) return;
+
+ // First remove any existing loop unrolling metadata.
+ SmallVector<Metadata *, 4> MDs;
+ // Reserve first location for self reference to the LoopID metadata node.
+ MDs.push_back(nullptr);
+ for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
+ bool IsUnrollMetadata = false;
+ MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
+ if (MD) {
+ const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
+ IsUnrollMetadata = S && S->getString().startswith("llvm.loop.unroll.");
+ }
+ if (!IsUnrollMetadata)
+ MDs.push_back(LoopID->getOperand(i));
+ }
+
+ // Add unroll(disable) metadata to disable future unrolling.
+ LLVMContext &Context = L->getHeader()->getContext();
+ SmallVector<Metadata *, 1> DisableOperands;
+ DisableOperands.push_back(MDString::get(Context, "llvm.loop.unroll.disable"));
+ MDNode *DisableNode = MDNode::get(Context, DisableOperands);
+ MDs.push_back(DisableNode);
+
+ MDNode *NewLoopID = MDNode::get(Context, MDs);
+ // Set operand 0 to refer to the loop id itself.
+ NewLoopID->replaceOperandWith(0, NewLoopID);
+ L->setLoopID(NewLoopID);
+}
+
+unsigned LoopUnroll::selectUnrollCount(
+ const Loop *L, unsigned TripCount, bool PragmaFullUnroll,
+ unsigned PragmaCount, const TargetTransformInfo::UnrollingPreferences &UP,
+ bool &SetExplicitly) {
+ SetExplicitly = true;
+
+ // User-specified count (either as a command-line option or
+ // constructor parameter) has highest precedence.
+ unsigned Count = UserCount ? CurrentCount : 0;
+
+ // If there is no user-specified count, unroll pragmas have the next
+ // highest precendence.
+ if (Count == 0) {
+ if (PragmaCount) {
+ Count = PragmaCount;
+ } else if (PragmaFullUnroll) {
+ Count = TripCount;
+ }
+ }
+
+ if (Count == 0)
+ Count = UP.Count;
+
+ if (Count == 0) {
+ SetExplicitly = false;
+ if (TripCount == 0)
+ // Runtime trip count.
+ Count = UnrollRuntimeCount;
+ else
+ // Conservative heuristic: if we know the trip count, see if we can
+ // completely unroll (subject to the threshold, checked below); otherwise
+ // try to find greatest modulo of the trip count which is still under
+ // threshold value.
+ Count = TripCount;
+ }
+ if (TripCount && Count > TripCount)
+ return TripCount;
+ return Count;
+}
+
bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
-
- LoopInfo *LI = &getAnalysis<LoopInfo>();
+ if (skipOptnoneFunction(L))
+ return false;
+
+ Function &F = *L->getHeader()->getParent();
+
+ LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+ ScalarEvolution *SE = &getAnalysis<ScalarEvolution>();
+ const TargetTransformInfo &TTI =
+ getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+ const FunctionTargetTransformInfo &FTTI =
+ getAnalysis<FunctionTargetTransformInfo>();
+ auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
BasicBlock *Header = L->getHeader();
DEBUG(dbgs() << "Loop Unroll: F[" << Header->getParent()->getName()
<< "] Loop %" << Header->getName() << "\n");
- (void)Header;
-
- // 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 optimize-for-size, and the unroll threshold was
- // not user specified.
- CurrentThreshold = UnrollThreshold;
- if (Header->getParent()->hasFnAttr(Attribute::OptimizeForSize) &&
- UnrollThreshold.getNumOccurrences() == 0)
- CurrentThreshold = OptSizeUnrollThreshold;
-
- // Find trip count
- unsigned TripCount = L->getSmallConstantTripCount();
- unsigned Count = UnrollCount;
-
- // Automatically select an unroll count.
- if (Count == 0) {
- // Conservative heuristic: if we know the trip count, see if we can
- // completely unroll (subject to the threshold, checked below); otherwise
- // try to find greatest modulo of the trip count which is still under
- // threshold value.
- if (TripCount == 0)
- return false;
- Count = TripCount;
+
+ if (HasUnrollDisablePragma(L)) {
+ return false;
}
+ bool PragmaFullUnroll = HasUnrollFullPragma(L);
+ unsigned PragmaCount = UnrollCountPragmaValue(L);
+ bool HasPragma = PragmaFullUnroll || PragmaCount > 0;
- // Enforce the threshold.
- if (CurrentThreshold != NoThreshold) {
- unsigned NumCalls;
- unsigned LoopSize = ApproximateLoopSize(L, NumCalls);
- DEBUG(dbgs() << " Loop Size = " << LoopSize << "\n");
- if (NumCalls != 0) {
- // Even for a loop that contains calls, it can still be profitable to
- // unroll if the loop is really, REALLY small.
- DEBUG(dbgs() <<" Using lower threshold for loop with function calls.\n");
- CurrentThreshold = OptSizeUnrollThreshold;
- }
- uint64_t Size = (uint64_t)LoopSize*Count;
- if (TripCount != 1 && Size > CurrentThreshold) {
+ TargetTransformInfo::UnrollingPreferences UP;
+ getUnrollingPreferences(L, FTTI, UP);
+
+ // Find trip count and trip multiple if count is not available
+ unsigned TripCount = 0;
+ unsigned TripMultiple = 1;
+ // If there are multiple exiting blocks but one of them is the latch, use the
+ // latch for the trip count estimation. Otherwise insist on a single exiting
+ // block for the trip count estimation.
+ BasicBlock *ExitingBlock = L->getLoopLatch();
+ if (!ExitingBlock || !L->isLoopExiting(ExitingBlock))
+ ExitingBlock = L->getExitingBlock();
+ if (ExitingBlock) {
+ TripCount = SE->getSmallConstantTripCount(L, ExitingBlock);
+ TripMultiple = SE->getSmallConstantTripMultiple(L, ExitingBlock);
+ }
+
+ // Select an initial unroll count. This may be reduced later based
+ // on size thresholds.
+ bool CountSetExplicitly;
+ unsigned Count = selectUnrollCount(L, TripCount, PragmaFullUnroll,
+ PragmaCount, UP, CountSetExplicitly);
+
+ unsigned NumInlineCandidates;
+ bool notDuplicatable;
+ unsigned LoopSize =
+ ApproximateLoopSize(L, NumInlineCandidates, notDuplicatable, TTI, &AC);
+ DEBUG(dbgs() << " Loop Size = " << LoopSize << "\n");
+
+ // When computing the unrolled size, note that the conditional branch on the
+ // backedge and the comparison feeding it are not replicated like the rest of
+ // the loop body (which is why 2 is subtracted).
+ uint64_t UnrolledSize = (uint64_t)(LoopSize-2) * Count + 2;
+ if (notDuplicatable) {
+ DEBUG(dbgs() << " Not unrolling loop which contains non-duplicatable"
+ << " instructions.\n");
+ return false;
+ }
+ if (NumInlineCandidates != 0) {
+ DEBUG(dbgs() << " Not unrolling loop with inlinable calls.\n");
+ return false;
+ }
+
+ unsigned Threshold, PartialThreshold;
+ selectThresholds(L, HasPragma, UP, Threshold, PartialThreshold);
+
+ // Given Count, TripCount and thresholds determine the type of
+ // unrolling which is to be performed.
+ enum { Full = 0, Partial = 1, Runtime = 2 };
+ int Unrolling;
+ if (TripCount && Count == TripCount) {
+ if (Threshold != NoThreshold && UnrolledSize > Threshold) {
DEBUG(dbgs() << " Too large to fully unroll with count: " << Count
- << " because size: " << Size << ">" << CurrentThreshold << "\n");
- if (!UnrollAllowPartial) {
- DEBUG(dbgs() << " will not try to unroll partially because "
- << "-unroll-allow-partial not given\n");
- return false;
- }
- // Reduce unroll count to be modulo of TripCount for partial unrolling
- Count = CurrentThreshold / LoopSize;
- while (Count != 0 && TripCount%Count != 0) {
+ << " because size: " << UnrolledSize << ">" << Threshold
+ << "\n");
+ Unrolling = Partial;
+ } else {
+ Unrolling = Full;
+ }
+ } else if (TripCount && Count < TripCount) {
+ Unrolling = Partial;
+ } else {
+ Unrolling = Runtime;
+ }
+
+ // Reduce count based on the type of unrolling and the threshold values.
+ unsigned OriginalCount = Count;
+ bool AllowRuntime = UserRuntime ? CurrentRuntime : UP.Runtime;
+ if (Unrolling == Partial) {
+ bool AllowPartial = UserAllowPartial ? CurrentAllowPartial : UP.Partial;
+ if (!AllowPartial && !CountSetExplicitly) {
+ DEBUG(dbgs() << " will not try to unroll partially because "
+ << "-unroll-allow-partial not given\n");
+ return false;
+ }
+ if (PartialThreshold != NoThreshold && UnrolledSize > PartialThreshold) {
+ // Reduce unroll count to be modulo of TripCount for partial unrolling.
+ Count = (std::max(PartialThreshold, 3u)-2) / (LoopSize-2);
+ while (Count != 0 && TripCount % Count != 0)
Count--;
+ }
+ } else if (Unrolling == Runtime) {
+ if (!AllowRuntime && !CountSetExplicitly) {
+ DEBUG(dbgs() << " will not try to unroll loop with runtime trip count "
+ << "-unroll-runtime not given\n");
+ return false;
+ }
+ // Reduce unroll count to be the largest power-of-two factor of
+ // the original count which satisfies the threshold limit.
+ while (Count != 0 && UnrolledSize > PartialThreshold) {
+ Count >>= 1;
+ UnrolledSize = (LoopSize-2) * Count + 2;
+ }
+ if (Count > UP.MaxCount)
+ Count = UP.MaxCount;
+ DEBUG(dbgs() << " partially unrolling with count: " << Count << "\n");
+ }
+
+ if (HasPragma) {
+ if (PragmaCount != 0)
+ // If loop has an unroll count pragma mark loop as unrolled to prevent
+ // unrolling beyond that requested by the pragma.
+ SetLoopAlreadyUnrolled(L);
+
+ // Emit optimization remarks if we are unable to unroll the loop
+ // as directed by a pragma.
+ DebugLoc LoopLoc = L->getStartLoc();
+ Function *F = Header->getParent();
+ LLVMContext &Ctx = F->getContext();
+ if (PragmaFullUnroll && PragmaCount == 0) {
+ if (TripCount && Count != TripCount) {
+ emitOptimizationRemarkMissed(
+ Ctx, DEBUG_TYPE, *F, LoopLoc,
+ "Unable to fully unroll loop as directed by unroll(full) pragma "
+ "because unrolled size is too large.");
+ } else if (!TripCount) {
+ emitOptimizationRemarkMissed(
+ Ctx, DEBUG_TYPE, *F, LoopLoc,
+ "Unable to fully unroll loop as directed by unroll(full) pragma "
+ "because loop has a runtime trip count.");
}
- if (Count < 2) {
- DEBUG(dbgs() << " could not unroll partially\n");
- return false;
- }
- DEBUG(dbgs() << " partially unrolling with count: " << Count << "\n");
+ } else if (PragmaCount > 0 && Count != OriginalCount) {
+ emitOptimizationRemarkMissed(
+ Ctx, DEBUG_TYPE, *F, LoopLoc,
+ "Unable to unroll loop the number of times directed by "
+ "unroll_count pragma because unrolled size is too large.");
}
}
+ if (Unrolling != Full && Count < 2) {
+ // Partial unrolling by 1 is a nop. For full unrolling, a factor
+ // of 1 makes sense because loop control can be eliminated.
+ return false;
+ }
+
// Unroll the loop.
- Function *F = L->getHeader()->getParent();
- if (!UnrollLoop(L, Count, LI, &LPM))
+ if (!UnrollLoop(L, Count, TripCount, AllowRuntime, TripMultiple, LI, this,
+ &LPM, &AC))
return false;
- // FIXME: Reconstruct dom info, because it is not preserved properly.
- if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>())
- DT->runOnFunction(*F);
return true;
}
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