// counts of loops easily.
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "loop-unroll"
-#include "llvm/IntrinsicInst.h"
#include "llvm/Transforms/Scalar.h"
+#include "llvm/Analysis/CodeMetrics.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/Dominators.h"
+#include "llvm/IR/IntrinsicInst.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(200), cl::Hidden,
+UnrollThreshold("unroll-threshold", cl::init(150), cl::Hidden,
cl::desc("The cut-off point for automatic loop unrolling"));
static cl::opt<unsigned>
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"));
+
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;
- bool runOnLoop(Loop *L, LPPassManager &LPM);
+ // 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) override;
/// This transformation requires natural loop information & requires that
/// loop preheaders be inserted into the CFG...
///
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
AU.addRequiredID(LoopSimplifyID);
AU.addPreservedID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
AU.addPreservedID(LCSSAID);
+ AU.addRequired<ScalarEvolution>();
+ AU.addPreserved<ScalarEvolution>();
+ AU.addRequired<TargetTransformInfo>();
// 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<DominanceFrontier>();
- AU.addPreserved<ScalarEvolution>();
+ AU.addPreserved<DominatorTreeWrapperPass>();
}
};
}
char LoopUnroll::ID = 0;
-INITIALIZE_PASS(LoopUnroll, "loop-unroll", "Unroll loops", false, false);
+INITIALIZE_PASS_BEGIN(LoopUnroll, "loop-unroll", "Unroll loops", false, false)
+INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
+INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+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) {
CodeMetrics Metrics;
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
I != E; ++I)
- Metrics.analyzeBasicBlock(*I);
- NumCalls = Metrics.NumCalls;
- return Metrics.NumInsts;
+ Metrics.analyzeBasicBlock(*I, TTI);
+ NumCalls = Metrics.NumInlineCandidates;
+ NotDuplicatable = Metrics.notDuplicatable;
+
+ unsigned LoopSize = Metrics.NumInsts;
+
+ // 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;
+
+ return LoopSize;
}
bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
+ if (skipOptnoneFunction(L))
+ return false;
+
LoopInfo *LI = &getAnalysis<LoopInfo>();
+ ScalarEvolution *SE = &getAnalysis<ScalarEvolution>();
+ const TargetTransformInfo &TTI = getAnalysis<TargetTransformInfo>();
BasicBlock *Header = L->getHeader();
DEBUG(dbgs() << "Loop Unroll: F[" << Header->getParent()->getName()
<< "] Loop %" << Header->getName() << "\n");
(void)Header;
- // Find trip count
- unsigned TripCount = L->getSmallConstantTripCount();
- unsigned Count = UnrollCount;
+ 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;
+ TTI.getUnrollingPreferences(L, UP);
+
+ // 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.
+ unsigned Threshold = UserThreshold ? CurrentThreshold : UP.Threshold;
+ unsigned PartialThreshold =
+ UserThreshold ? CurrentThreshold : UP.PartialThreshold;
+ if (!UserThreshold &&
+ Header->getParent()->getAttributes().
+ hasAttribute(AttributeSet::FunctionIndex,
+ Attribute::OptimizeForSize)) {
+ Threshold = UP.OptSizeThreshold;
+ PartialThreshold = UP.PartialOptSizeThreshold;
+ }
+
+ // Find trip count and trip multiple if count is not available
+ unsigned TripCount = 0;
+ unsigned TripMultiple = 1;
+ // Find "latch trip count". UnrollLoop assumes that control cannot exit
+ // via the loop latch on any iteration prior to TripCount. The loop may exit
+ // early via an earlier branch.
+ BasicBlock *LatchBlock = L->getLoopLatch();
+ if (LatchBlock) {
+ TripCount = SE->getSmallConstantTripCount(L, LatchBlock);
+ TripMultiple = SE->getSmallConstantTripMultiple(L, LatchBlock);
+ }
+
+ bool Runtime = UserRuntime ? CurrentRuntime : UP.Runtime;
+
+ // Use a default unroll-count if the user doesn't specify a value
+ // and the trip count is a run-time value. The default is different
+ // for run-time or compile-time trip count loops.
+ unsigned Count = UserCount ? CurrentCount : UP.Count;
+ if (Runtime && Count == 0 && TripCount == 0)
+ Count = UnrollRuntimeCount;
- // 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
}
// Enforce the threshold.
- if (UnrollThreshold != NoThreshold) {
- unsigned NumCalls;
- unsigned LoopSize = ApproximateLoopSize(L, NumCalls);
+ if (Threshold != NoThreshold && PartialThreshold != NoThreshold) {
+ unsigned NumInlineCandidates;
+ bool notDuplicatable;
+ unsigned LoopSize = ApproximateLoopSize(L, NumInlineCandidates,
+ notDuplicatable, TTI);
DEBUG(dbgs() << " Loop Size = " << LoopSize << "\n");
- if (NumCalls != 0) {
- DEBUG(dbgs() << " Not unrolling loop with function calls.\n");
+ 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;
}
uint64_t Size = (uint64_t)LoopSize*Count;
- if (TripCount != 1 && Size > UnrollThreshold) {
+ if (TripCount != 1 && Size > Threshold) {
DEBUG(dbgs() << " Too large to fully unroll with count: " << Count
- << " because size: " << Size << ">" << UnrollThreshold << "\n");
- if (!UnrollAllowPartial) {
+ << " because size: " << Size << ">" << Threshold << "\n");
+ bool AllowPartial = UserAllowPartial ? CurrentAllowPartial : UP.Partial;
+ if (!AllowPartial && !(Runtime && TripCount == 0)) {
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 = UnrollThreshold / LoopSize;
- while (Count != 0 && TripCount%Count != 0) {
- Count--;
+ if (TripCount) {
+ // Reduce unroll count to be modulo of TripCount for partial unrolling
+ Count = PartialThreshold / LoopSize;
+ while (Count != 0 && TripCount%Count != 0)
+ Count--;
+ }
+ else if (Runtime) {
+ // Reduce unroll count to be a lower power-of-two value
+ while (Count != 0 && Size > PartialThreshold) {
+ Count >>= 1;
+ Size = LoopSize*Count;
+ }
}
+ if (Count > UP.MaxCount)
+ Count = UP.MaxCount;
if (Count < 2) {
DEBUG(dbgs() << " could not unroll partially\n");
return false;
}
// Unroll the loop.
- Function *F = L->getHeader()->getParent();
- if (!UnrollLoop(L, Count, LI, &LPM))
+ if (!UnrollLoop(L, Count, TripCount, Runtime, TripMultiple, LI, this, &LPM))
return false;
- // FIXME: Reconstruct dom info, because it is not preserved properly.
- DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>();
- if (DT) {
- DT->runOnFunction(*F);
- DominanceFrontier *DF = getAnalysisIfAvailable<DominanceFrontier>();
- if (DF)
- DF->runOnFunction(*F);
- }
return true;
}
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