[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
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index c09530c..2773b60 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -558,12 +558,18 @@
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);