Revert "Transforms: reapply SVN r219899"

This reverts commit r220811 and r220839. It made an incorrect change to
musttail handling.

llvm-svn: 221226

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 8f6855e6a30..6fe5e188b1a 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -253,7 +253,12 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
     return false;
   AllCallsAreTailCalls = true;
 
+  // The local stack holds all alloca instructions and all byval arguments.
   AllocaDerivedValueTracker Tracker;
+  for (Argument &Arg : F.args()) {
+    if (Arg.hasByValAttr())
+      Tracker.walk(&Arg);
+  }
   for (auto &BB : F) {
     for (auto &I : BB)
       if (AllocaInst *AI = dyn_cast<AllocaInst>(&I))
@@ -309,8 +314,9 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
         for (auto &Arg : CI->arg_operands()) {
           if (isa<Constant>(Arg.getUser()))
             continue;
-          if (isa<Argument>(Arg.getUser()))
-            continue;
+          if (Argument *A = dyn_cast<Argument>(Arg.getUser()))
+            if (!A->hasByValAttr())
+              continue;
           SafeToTail = false;
           break;
         }