OpaquePtr: Don't check pointee type for byval/preallocated

Since none of these users really care about the actual type, hide the
type under a new size-getting attribute to go along with
hasPassPointeeByValueAttr. This will work better for the future byref
attribute, which may end up only tracking the byte size and not the IR
type.

We currently have 3 parameter attributes that should carry the type
(technically inalloca does not yet). The APIs are somewhat awkward
since preallocated/inalloca piggyback on byval in some places, but in
others are treated as distinct attributes. Since these are all
mutually exclusive, we should probably just merge all the attribute
infrastructure treating these as totally distinct attributes.

Author: arsenm

llvm/include/llvm/IR/Argument.h

@@ -75,6 +75,10 @@ class Argument final : public Value {
   /// attribute. These attributes represent arguments being passed by value.
   bool hasPassPointeeByValueAttr() const;
 
+  /// If this argument satisfies has hasPassPointeeByValueAttr, return the
+  /// in-memory ABI size copied to the stack for the call. Otherwise, return 0.
+  uint64_t getPassPointeeByValueCopySize(const DataLayout &DL) const;
+
   /// If this is a byval or inalloca argument, return its alignment.
   /// FIXME: Remove this function once transition to Align is over.
   /// Use getParamAlign() instead.

llvm/lib/IR/Function.cpp

@@ -128,6 +128,27 @@ bool Argument::hasPassPointeeByValueAttr() const {
          Attrs.hasParamAttribute(getArgNo(), Attribute::Preallocated);
 }
 
+uint64_t Argument::getPassPointeeByValueCopySize(const DataLayout &DL) const {
+  AttributeSet ParamAttrs
+    = getParent()->getAttributes().getParamAttributes(getArgNo());
+
+  // FIXME: All the type carrying attributes are mutually exclusive, so there
+  // should be a single query to get the stored type that handles any of them.
+  if (Type *ByValTy = ParamAttrs.getByValType())
+    return DL.getTypeAllocSize(ByValTy);
+  if (Type *PreAllocTy = ParamAttrs.getPreallocatedType())
+    return DL.getTypeAllocSize(PreAllocTy);
+
+  // FIXME: inalloca always depends on pointee element type. It's also possible
+  // for byval to miss it.
+  if (ParamAttrs.hasAttribute(Attribute::InAlloca) ||
+      ParamAttrs.hasAttribute(Attribute::ByVal) ||
+      ParamAttrs.hasAttribute(Attribute::Preallocated))
+    return DL.getTypeAllocSize(cast<PointerType>(getType())->getElementType());
+
+  return 0;
+}
+
 unsigned Argument::getParamAlignment() const {
   assert(getType()->isPointerTy() && "Only pointers have alignments");
   return getParent()->getParamAlignment(getArgNo());

llvm/lib/IR/Mangler.cpp

@@ -94,15 +94,18 @@ static void addByteCountSuffix(raw_ostream &OS, const Function *F,
                                const DataLayout &DL) {
   // Calculate arguments size total.
   unsigned ArgWords = 0;
+
+  const unsigned PtrSize = DL.getPointerSize();
+
   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
        AI != AE; ++AI) {
-    Type *Ty = AI->getType();
     // 'Dereference' type in case of byval or inalloca parameter attribute.
-    if (AI->hasPassPointeeByValueAttr())
-      Ty = cast<PointerType>(Ty)->getElementType();
+    uint64_t AllocSize = AI->hasPassPointeeByValueAttr() ?
+      AI->getPassPointeeByValueCopySize(DL) :
+      DL.getTypeAllocSize(AI->getType());
+
     // Size should be aligned to pointer size.
-    unsigned PtrSize = DL.getPointerSize();
-    ArgWords += alignTo(DL.getTypeAllocSize(Ty), PtrSize);
+    ArgWords += alignTo(AllocSize, PtrSize);
   }
 
   OS << '@' << ArgWords;