[Utils] Use WeakTrackingVH in vector used as scratch storage.

The utility method RecursivelyDeleteTriviallyDeadInstructions receives
as input a vector of Instructions, where all inputs are valid
instructions. This same vector is used as a scratch storage (per the
header comment) to recursively delete instructions. If an instruction is
added as an operand of multiple other instructions, it may be added twice,
then deleted once, then the second reference in the vector is invalid.
Switch to using a Vector<WeakTrackingVH>.
This change facilitates a clean-up in LoopStrengthReduction.

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp b/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
index 9012041..3153a87 100644
--- a/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
@@ -68,7 +68,7 @@ static bool simplifyLoopInst(Loop &L, DominatorTree &DT, LoopInfo &LI,
 
   // While simplifying we may discover dead code or cause code to become dead.
   // Keep track of all such instructions and we will delete them at the end.
-  SmallVector<Instruction *, 8> DeadInsts;
+  SmallVector<WeakTrackingVH, 8> DeadInsts;
 
   // First we want to create an RPO traversal of the loop body. By processing in
   // RPO we can ensure that definitions are processed prior to uses (for non PHI