diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3395,6 +3395,10 @@
     if (CallerPAL.hasParamAttr(i, Attribute::SwiftError))
       return false;
 
+    if (!CallerPAL.hasParamAttr(i, Attribute::ByVal) &&
+        Callee->getAttributes().hasParamAttr(i, Attribute::ByVal))
+      return false; // Cannot transform to byval.
+
     // If the parameter is passed as a byval argument, then we have to have a
     // sized type and the sized type has to have the same size as the old type.
     if (ParamTy != ActTy && CallerPAL.hasParamAttr(i, Attribute::ByVal)) {