[FuzzMutate] Don't insert instructions after musttail call

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/FuzzMutate/IRMutator.cpp b/llvm/lib/FuzzMutate/IRMutator.cpp
index 105f8bc6c522..0f93bf9ee9c8 100644
--- a/llvm/lib/FuzzMutate/IRMutator.cpp
+++ b/llvm/lib/FuzzMutate/IRMutator.cpp
@@ -116,6 +116,16 @@ void InjectorIRStrategy::mutate(BasicBlock &BB, RandomIRBuilder &IB) {
   auto InstsBefore = makeArrayRef(Insts).slice(0, IP);
   auto InstsAfter = makeArrayRef(Insts).slice(IP);
 
+  if (!InstsBefore.empty()) {
+    // Don't insert instructions after a musttail call.
+    Instruction *InstBefore = InstsBefore.back();
+    if (isa<BitCastInst>(InstBefore))
+      InstBefore = InstBefore->getPrevNode();
+    CallBase *CallBefore = dyn_cast_or_null<CallBase>(InstBefore);
+    if (CallBefore && CallBefore->isMustTailCall())
+      return;
+  }
+
   // Choose a source, which will be used to constrain the operation selection.
   SmallVector<Value *, 2> Srcs;
   Srcs.push_back(IB.findOrCreateSource(BB, InstsBefore));