[clang] [CIR] Add pass_object_size hidden parameter support (PR #191482)

[via cfe-commits]

================
@@ -708,20 +708,26 @@ static CanQual<FunctionProtoType> getFormalType(const CXXMethodDecl *md) {
       .getAs<FunctionProtoType>();
 }
 
-/// Adds the formal parameters in FPT to the given prefix. If any parameter in
-/// FPT has pass_object_size_attrs, then we'll add parameters for those, too.
+/// Adds the formal parameters in FPT to the given prefix.  If any parameter in
+/// FPT has pass_object_size attrs, then we'll add parameters for those, too.
 /// TODO(cir): this should be shared with LLVM codegen
 static void appendParameterTypes(const CIRGenTypes &cgt,
                                  SmallVectorImpl<CanQualType> &prefix,
                                  CanQual<FunctionProtoType> fpt) {
-  assert(!cir::MissingFeatures::opCallExtParameterInfo());
   // Fast path: don't touch param info if we don't need to.
   if (!fpt->hasExtParameterInfos()) {
     prefix.append(fpt->param_type_begin(), fpt->param_type_end());
     return;
   }
 
-  cgt.getCGModule().errorNYI("appendParameterTypes: hasExtParameterInfos");
+  prefix.reserve(prefix.size() + fpt->getNumParams());
+  auto extInfos = fpt->getExtParameterInfos();
+  for (unsigned i = 0, e = fpt->getNumParams(); i != e; ++i) {
+    prefix.push_back(fpt->getParamType(i));
+    if (extInfos[i].hasPassObjectSize())
+      prefix.push_back(cgt.getASTContext().getCanonicalType(
+          cgt.getASTContext().getSizeType()));
----------------
adams381 wrote:

Yes, that's what we use now: `cgt.getASTContext().getCanonicalSizeType()`.  Matches classic codegen's `CGT.getContext().getCanonicalSizeType()` (our accessor is named `getASTContext()` to avoid ambiguity with MLIR/LLVM contexts).

https://github.com/llvm/llvm-project/pull/191482