Don't assume a tail call can't reference a byval

argument to the outer function, this isn't correct.

llvm-svn: 49731

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index b696a800cf6..ad462076385 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -273,8 +273,10 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
 
       // If this is a tail call and P points to a stack location, we know that
       // the tail call cannot access or modify the local stack.
-      if (isa<AllocaInst>(Object) ||
-          (isa<Argument>(Object) && cast<Argument>(Object)->hasByValAttr()))
+      // We cannot exclude byval arguments here; these belong to the caller of
+      // the current function not to the current function, and a tail callee
+      // may reference them.
+      if (isa<AllocaInst>(Object))
         if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
           if (CI->isTailCall())
             return NoModRef;