musttail: Don't eliminate varargs packs if there is a forwarding call

Also clean up and beef up this grep test for the feature.

llvm-svn: 216425

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
index ac3853dbd67..7b22e921814 100644
--- a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -199,10 +199,15 @@ bool DAE::DeleteDeadVarargs(Function &Fn) {
     return false;
 
   // Okay, we know we can transform this function if safe.  Scan its body
-  // looking for calls to llvm.vastart.
+  // looking for calls marked musttail or calls to llvm.vastart.
   for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
     for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
-      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+      CallInst *CI = dyn_cast<CallInst>(I);
+      if (!CI)
+        continue;
+      if (CI->isMustTailCall())
+        return false;
+      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
         if (II->getIntrinsicID() == Intrinsic::vastart)
           return false;
       }