Add the `pass_object_size` attribute to clang.

`pass_object_size` is our way of enabling `__builtin_object_size` to
produce high quality results without requiring inlining to happen
everywhere.

A link to the design doc for this attribute is available at the
Differential review link below.

Differential Revision: http://reviews.llvm.org/D13263

llvm-svn: 254554

1 files changed, 14 insertions, 2 deletions

diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index c1c2d2d1a45..3651673ffd2 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1841,8 +1841,20 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
     Out << 'X';
   } else {
     // Happens for function pointer type arguments for example.
-    for (const QualType &Arg : Proto->param_types())
-      mangleArgumentType(Arg, Range);
+    for (unsigned I = 0, E = Proto->getNumParams(); I != E; ++I) {
+      mangleArgumentType(Proto->getParamType(I), Range);
+      // Mangle each pass_object_size parameter as if it's a paramater of enum
+      // type passed directly after the parameter with the pass_object_size
+      // attribute. The aforementioned enum's name is __pass_object_size, and we
+      // pretend it resides in a top-level namespace called __clang.
+      //
+      // FIXME: Is there a defined extension notation for the MS ABI, or is it
+      // necessary to just cross our fingers and hope this type+namespace
+      // combination doesn't conflict with anything?
+      if (D)
+        if (auto *P = D->getParamDecl(I)->getAttr<PassObjectSizeAttr>())
+          Out << "W4__pass_object_size" << P->getType() << "@__clang@@";
+    }
     // <builtin-type>      ::= Z  # ellipsis
     if (Proto->isVariadic())
       Out << 'Z';