diff options
Diffstat (limited to 'llvm/lib/Transforms/Utils')
| -rw-r--r-- | llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp index 3606ec4b9fc..386621844fe 100644 --- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp +++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp @@ -70,6 +70,17 @@ static void ConnectProlog(Loop *L, Value *BECount, unsigned Count, BasicBlock *PreHeader, BasicBlock *NewPreHeader, ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA) { + // Loop structure should be the following: + // Preheader + // PrologPreHeader + // ... + // PrologLatch + // PrologExit + // NewPreheader + // Header + // ... + // Latch + // LatchExit BasicBlock *Latch = L->getLoopLatch(); assert(Latch && "Loop must have a latch"); BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]); @@ -83,14 +94,21 @@ static void ConnectProlog(Loop *L, Value *BECount, unsigned Count, for (PHINode &PN : Succ->phis()) { // Add a new PHI node to the prolog end block and add the // appropriate incoming values. + // TODO: This code assumes that the PrologExit (or the LatchExit block for + // prolog loop) contains only one predecessor from the loop, i.e. the + // PrologLatch. When supporting multiple-exiting block loops, we can have + // two or more blocks that have the LatchExit as the target in the + // original loop. PHINode *NewPN = PHINode::Create(PN.getType(), 2, PN.getName() + ".unr", PrologExit->getFirstNonPHI()); // Adding a value to the new PHI node from the original loop preheader. // This is the value that skips all the prolog code. if (L->contains(&PN)) { + // Succ is loop header. NewPN->addIncoming(PN.getIncomingValueForBlock(NewPreHeader), PreHeader); } else { + // Succ is LatchExit NewPN->addIncoming(UndefValue::get(PN.getType()), PreHeader); } |
