[SimplifyCFG] Stop inserting calls to llvm.trap for UB

SimplifyCFG had logic to insert calls to llvm.trap for two very
particular IR patterns: stores and invokes of undef/null.

While InstCombine canonicalizes certain undefined behavior IR patterns
to stores of undef, phase ordering means that this cannot be relied upon
in general.

There are much better tools than llvm.trap: UBSan and ASan.

N.B. I could be argued into reverting this change if a clear argument as
to why it is important that we synthesize llvm.trap for stores, I'd be
hard pressed to see why it'd be useful for invokes...

llvm-svn: 273778

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/IPO/PruneEH.cpp b/llvm/lib/Transforms/IPO/PruneEH.cpp
index 04383f4f3fa..abde3d3609a 100644
--- a/llvm/lib/Transforms/IPO/PruneEH.cpp
+++ b/llvm/lib/Transforms/IPO/PruneEH.cpp
@@ -258,7 +258,7 @@ void PruneEH::DeleteBasicBlock(BasicBlock *BB) {
 
   if (TokenInst) {
     if (!isa<TerminatorInst>(TokenInst))
-      changeToUnreachable(TokenInst->getNextNode(), /*UseLLVMTrap=*/false);
+      changeToUnreachable(TokenInst->getNextNode());
   } else {
     // Get the list of successors of this block.
     std::vector<BasicBlock *> Succs(succ_begin(BB), succ_end(BB));