1 files changed, 156 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
new file mode 100644
index 0000000..4ad41ae
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -0,0 +1,156 @@
+//===-- LoopUnroll.cpp - Loop unroller pass -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass implements a simple loop unroller.  It works best when loops have
+// been canonicalized by the -indvars pass, allowing it to determine the trip
+// counts of loops easily.
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "loop-unroll"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/InlineCost.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/UnrollLoop.h"
+#include <climits>
+
+using namespace llvm;
+
+static cl::opt<unsigned>
+UnrollThreshold("unroll-threshold", cl::init(100), 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"));
+
+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 LoopUnroll : public LoopPass {
+  public:
+    static char ID; // Pass ID, replacement for typeid
+    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
+    /// code expansion would result.
+    static const unsigned NoThreshold = UINT_MAX;
+
+    bool runOnLoop(Loop *L, LPPassManager &LPM);
+
+    /// This transformation requires natural loop information & requires that
+    /// loop preheaders be inserted into the CFG...
+    ///
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequiredID(LoopSimplifyID);
+      AU.addRequiredID(LCSSAID);
+      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");
+
+Pass *llvm::createLoopUnrollPass() { return new LoopUnroll(); }
+
+/// ApproximateLoopSize - Approximate the size of the loop.
+static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls) {
+  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;
+}
+
+bool LoopUnroll::runOnLoop(Loop *L, LPPassManager &LPM) {
+  LoopInfo *LI = &getAnalysis<LoopInfo>();
+
+  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;
+
+  // 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;
+  }
+
+  // Enforce the threshold.
+  if (UnrollThreshold != NoThreshold) {
+    unsigned NumCalls;
+    unsigned LoopSize = ApproximateLoopSize(L, NumCalls);
+    DEBUG(dbgs() << "  Loop Size = " << LoopSize << "\n");
+    if (NumCalls != 0) {
+      DEBUG(dbgs() << "  Not unrolling loop with function calls.\n");
+      return false;
+    }
+    uint64_t Size = (uint64_t)LoopSize*Count;
+    if (TripCount != 1 && Size > UnrollThreshold) {
+      DEBUG(dbgs() << "  Too large to fully unroll with count: " << Count
+            << " because size: " << Size << ">" << UnrollThreshold << "\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 = UnrollThreshold / LoopSize;
+      while (Count != 0 && TripCount%Count != 0) {
+        Count--;
+      }
+      if (Count < 2) {
+        DEBUG(dbgs() << "  could not unroll partially\n");
+        return false;
+      }
+      DEBUG(dbgs() << "  partially unrolling with count: " << Count << "\n");
+    }
+  }
+
+  // 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;
+}