[PATCH] D25868: Loop Utils: Cloning any level loop nest

[Vinay Madhusudan via llvm-commits]

mivnay created this revision.
mivnay added reviewers: hfinkel, anemet.
mivnay added a subscriber: llvm-commits.

Currently, only inner-most loops are allowed to be cloned. This changes the cloneLoopWithPreheader() function to clone any level loop. This also updates the DominatorTree and LoopInfo.

Thanks,
Vinay Madhusudan,
Compiler Tree Technologies


https://reviews.llvm.org/D25868

Files:
  lib/Transforms/Utils/CloneFunction.cpp


Index: lib/Transforms/Utils/CloneFunction.cpp
===================================================================
--- lib/Transforms/Utils/CloneFunction.cpp
+++ lib/Transforms/Utils/CloneFunction.cpp
@@ -684,6 +684,22 @@
                        RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 }
 
+/// \brief Clones the original loop \p OrigLoop structure
+/// and keeps it ready to add the basic blocks.
+static void createNewLoops(Loop *OrigLoop, LoopInfo *LI, Loop *ParentLoop,
+   std::map<Loop*, Loop*>  &ClonedLoopMap) {
+  if (OrigLoop->empty()) return;
+
+  for (auto CurrLoop :  OrigLoop->getSubLoops()) {
+    Loop *NewLoop = new Loop();
+    ParentLoop->addChildLoop(NewLoop);
+    ClonedLoopMap[CurrLoop] = NewLoop;
+
+    // Recursively add the new loops.
+    createNewLoops(CurrLoop, LI, NewLoop, ClonedLoopMap);
+  }
+}
+
 /// \brief Clones a loop \p OrigLoop.  Returns the loop and the blocks in \p
 /// Blocks.
 ///
@@ -694,8 +710,6 @@
                                    const Twine &NameSuffix, LoopInfo *LI,
                                    DominatorTree *DT,
                                    SmallVectorImpl<BasicBlock *> &Blocks) {
-  assert(OrigLoop->getSubLoops().empty() && 
-         "Loop to be cloned cannot have inner loop");
   Function *F = OrigLoop->getHeader()->getParent();
   Loop *ParentLoop = OrigLoop->getParentLoop();
 
@@ -705,6 +719,14 @@
   else
     LI->addTopLevelLoop(NewLoop);
 
+  // Map each old Loop with new one.
+  std::map<Loop*, Loop*> ClonedLoopMap;
+  // Add the top level loop provided for cloning.
+  ClonedLoopMap[OrigLoop] = NewLoop;
+
+  // Recursively clone the loop structure.
+  createNewLoops(OrigLoop, LI, NewLoop, ClonedLoopMap);
+
   BasicBlock *OrigPH = OrigLoop->getLoopPreheader();
   assert(OrigPH && "No preheader");
   BasicBlock *NewPH = CloneBasicBlock(OrigPH, VMap, NameSuffix, F);
@@ -723,8 +745,13 @@
     BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix, F);
     VMap[BB] = NewBB;
 
+    // Get the innermost loop for the BB.
+    Loop* L = LI->getLoopFor(BB);
+    // Get the corresponding cloned loop.
+    Loop* NewClonedLoop = ClonedLoopMap[L];
+    assert(NewClonedLoop && "Could not find the corresponding cloned loop");
     // Update LoopInfo.
-    NewLoop->addBasicBlockToLoop(NewBB, *LI);
+    NewClonedLoop->addBasicBlockToLoop(NewBB, *LI);
 
     // Add DominatorTree node. After seeing all blocks, update to correct IDom.
     DT->addNewBlock(NewBB, NewPH);


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