[LoopUnroll] Add check to Latch's terminator in UnrollRuntimeLoopRemainder
In this patch, I'm adding an extra check to the Latch's terminator in llvm::UnrollRuntimeLoopRemainder,
similar to how it is already done in the llvm::UnrollLoop.
The compiler would crash if this function is called with a malformed loop.
Patch by Rodrigo Caetano Rocha!
Differential Revision: https://reviews.llvm.org/D51486
llvm-svn: 342958
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index ce078ab..3361883 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -545,13 +545,27 @@
BasicBlock *Header = L->getHeader();
BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
+
+ if (!LatchBR || LatchBR->isUnconditional()) {
+ // The loop-rotate pass can be helpful to avoid this in many cases.
+ LLVM_DEBUG(
+ dbgs()
+ << "Loop latch not terminated by a conditional branch.\n");
+ return false;
+ }
+
unsigned ExitIndex = LatchBR->getSuccessor(0) == Header ? 1 : 0;
BasicBlock *LatchExit = LatchBR->getSuccessor(ExitIndex);
- // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
- // targets of the Latch be an exit block out of the loop. This needs
- // to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
- assert(!L->contains(LatchExit) &&
- "one of the loop latch successors should be the exit block!");
+
+ if (L->contains(LatchExit)) {
+ // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
+ // targets of the Latch be an exit block out of the loop.
+ LLVM_DEBUG(
+ dbgs()
+ << "One of the loop latch successors must be the exit block.\n");
+ return false;
+ }
+
// These are exit blocks other than the target of the latch exiting block.
SmallVector<BasicBlock *, 4> OtherExits;
bool isMultiExitUnrollingEnabled =