[Cloning] cloneLoopWithPreheader(): add assert to ensure no sub-loops

Summary:
cloneLoopWithPreheader() does not update LoopInfo for sub-loop of
the original loop being cloned. Add assert to ensure no sub-loops for loop being cloned.

Reviewers: anemet, ashutosh.nema, hfinkel

Subscribers: mzolotukhin, llvm-commits

Differential Revision: http://reviews.llvm.org/D15922

llvm-svn: 267671

2 files changed, 3 insertions, 0 deletions

diff --git a/llvm/include/llvm/Transforms/Utils/Cloning.h b/llvm/include/llvm/Transforms/Utils/Cloning.h
index 4f006f2adee..6adc58e2e98 100644
--- a/llvm/include/llvm/Transforms/Utils/Cloning.h
+++ b/llvm/include/llvm/Transforms/Utils/Cloning.h
@@ -221,6 +221,7 @@ bool InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
 ///
 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
 /// \p LoopDomBB.  Insert the new blocks before block specified in \p Before.
+/// Note: Only innermost loops are supported.
 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
                              Loop *OrigLoop, ValueToValueMapTy &VMap,
                              const Twine &NameSuffix, LoopInfo *LI,
diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index f2d929f555c..c8d12129861 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -672,6 +672,8 @@ Loop *llvm::cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
                                    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();