From 9108c2b92155decd107489f2069907b44f234250 Mon Sep 17 00:00:00 2001 From: David Green Date: Tue, 25 Sep 2018 10:08:47 +0000 Subject: [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 --- llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) (limited to 'llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp') diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp index ce078ab8f7b..3361883acd0 100644 --- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp +++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp @@ -545,13 +545,27 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count, BasicBlock *Header = L->getHeader(); BranchInst *LatchBR = cast(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 OtherExits; bool isMultiExitUnrollingEnabled = -- cgit v1.2.3