[RuntimeLoopUnroller] Add assert that we dont unroll non-rotated loops
Summary:
Cloning basic blocks in the loop for runtime loop unroller depends on loop being
in rotated form (i.e. loop latch target is the exit block).
Assert that this is true, so that callers of runtime loop unroller pass in
canonical loops.
The single caller of this function has that check recently added:
https://reviews.llvm.org/rL301239
Reviewers: davide
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D32801
llvm-svn: 302058
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 85db734..305b87e 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -512,6 +512,13 @@
BasicBlock *Latch = L->getLoopLatch();
+ // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
+ // targets of the Latch be the single exit block out of the loop. This needs
+ // to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
+ BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
+ assert(LatchBR->getSuccessor(0) == Exit ||
+ LatchBR->getSuccessor(1) == Exit && "loop latch successor should be "
+ "exit block!");
// Loop structure is the following:
//
// PreHeader