IR: add optional type to 'byval' function parameters

When we switch to opaque pointer types we will need some way to describe
how many bytes a 'byval' parameter should occupy on the stack. This adds
a (for now) optional extra type parameter.

If present, the type must match the pointee type of the argument.

Note to front-end maintainers: if this causes test failures, it's probably
because the "byval" attribute is printed after attributes without any parameter
after this change.

llvm-svn: 362012

llvm/lib/Bitcode/Writer/ValueEnumerator.cpp

@@ -949,9 +949,11 @@ void ValueEnumerator::incorporateFunction(const Function &F) {
   incorporateFunctionMetadata(F);
 
   // Adding function arguments to the value table.
-  for (const auto &I : F.args())
+  for (const auto &I : F.args()) {
     EnumerateValue(&I);
-
+    if (I.hasAttribute(Attribute::ByVal) && I.getParamByValType())
+      EnumerateType(I.getParamByValType());
+  }
   FirstFuncConstantID = Values.size();
 
   // Add all function-level constants to the value table.