From 2a4f26b4c28aaf9307e690b2f743ffcde5183b9e Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Tue, 13 Aug 2019 17:15:42 +0000 Subject: [ValueTracking] Improve reverse assumption inference Use isGuaranteedToTransferExecutionToSuccessor() instead of isSafeToSpeculativelyExecute() when seeing whether we can propagate the information in an assume backwards in isValidAssumeForContext(). The latter is more general - it also allows arbitrary loads/stores - and is also the condition we want: if our assume is guaranteed to execute, its condition not holding would be UB. Original patch by arielb1. Differential Revision: https://reviews.llvm.org/D37215 llvm-svn: 368723 --- llvm/lib/Analysis/ValueTracking.cpp | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'llvm/lib/Analysis/ValueTracking.cpp') diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index c09530cd697..2773b60bb75 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -558,12 +558,18 @@ bool llvm::isValidAssumeForContext(const Instruction *Inv, return true; } + // Don't let an assume affect itself - this would cause the problems + // `isEphemeralValueOf` is trying to prevent, and it would also make + // the loop below go out of bounds. + if (Inv == CxtI) + return false; + // The context comes first, but they're both in the same block. Make sure // there is nothing in between that might interrupt the control flow. for (BasicBlock::const_iterator I = std::next(BasicBlock::const_iterator(CxtI)), IE(Inv); I != IE; ++I) - if (!isSafeToSpeculativelyExecute(&*I) && !isAssumeLikeIntrinsic(&*I)) + if (!isGuaranteedToTransferExecutionToSuccessor(&*I)) return false; return !isEphemeralValueOf(Inv, CxtI); -- cgit v1.2.3