// counts of loops easily.
//===----------------------------------------------------------------------===//
-#include <climits>
#define DEBUG_TYPE "loop-unroll"
#include "llvm/IntrinsicInst.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/UnrollLoop.h"
+#include <climits>
using namespace llvm;
UnrollCount("unroll-count", cl::init(0), cl::Hidden,
cl::desc("Use this unroll count for all loops, 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."));
+
namespace {
class VISIBILITY_HIDDEN LoopUnroll : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
- LoopUnroll() : LoopPass((intptr_t)&ID) {}
+ LoopUnroll() : LoopPass(&ID) {}
/// A magic value for use with the Threshold parameter to indicate
/// that the loop unroll should be performed regardless of how much
AU.addRequired<LoopInfo>();
AU.addPreservedID(LCSSAID);
AU.addPreserved<LoopInfo>();
+ // 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>();
}
};
}
char LoopUnroll::ID = 0;
static RegisterPass<LoopUnroll> X("loop-unroll", "Unroll loops");
-LoopPass *llvm::createLoopUnrollPass() { return new LoopUnroll(); }
+Pass *llvm::createLoopUnrollPass() { return new LoopUnroll(); }
/// ApproximateLoopSize - Approximate the size of the loop.
static unsigned ApproximateLoopSize(const Loop *L) {
unsigned Size = 0;
- for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) {
- BasicBlock *BB = L->getBlocks()[i];
+ for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+ I != E; ++I) {
+ BasicBlock *BB = *I;
Instruction *Term = BB->getTerminator();
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (isa<PHINode>(I) && BB == L->getHeader()) {
// Ignore instructions only used by the loop terminator.
} else if (isa<DbgInfoIntrinsic>(I)) {
// Ignore debug instructions
+ } else if (isa<GetElementPtrInst>(I) && I->hasOneUse()) {
+ // Ignore GEP as they generally are subsumed into a load or store.
} else if (isa<CallInst>(I)) {
// Estimate size overhead introduced by call instructions which
// is higher than other instructions. Here 3 and 10 are magic
if (Count == 0) {
// Conservative heuristic: if we know the trip count, see if we can
// completely unroll (subject to the threshold, checked below); otherwise
- // don't unroll.
+ // try to find greatest modulo of the trip count which is still under
+ // threshold value.
if (TripCount != 0) {
Count = TripCount;
} else {
DOUT << " Loop Size = " << LoopSize << "\n";
uint64_t Size = (uint64_t)LoopSize*Count;
if (TripCount != 1 && Size > UnrollThreshold) {
- DOUT << " TOO LARGE TO UNROLL: "
- << Size << ">" << UnrollThreshold << "\n";
- return false;
+ DOUT << " Too large to fully unroll with count: " << Count
+ << " because size: " << Size << ">" << UnrollThreshold << "\n";
+ if (UnrollAllowPartial) {
+ // Reduce unroll count to be modulo of TripCount for partial unrolling
+ Count = UnrollThreshold / LoopSize;
+ while (Count != 0 && TripCount%Count != 0) {
+ Count--;
+ }
+ if (Count < 2) {
+ DOUT << " could not unroll partially\n";
+ return false;
+ } else {
+ DOUT << " partially unrolling with count: " << Count << "\n";
+ }
+ } else {
+ DOUT << " will not try to unroll partially because "
+ << "-unroll-allow-partial not given\n";
+ return false;
+ }
}
}
// Unroll the loop.
+ Function *F = L->getHeader()->getParent();
if (!UnrollLoop(L, Count, LI, &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;
}