Sema: diagnose PMFs passed through registers to inline assembly

The itanium ABI represents the PMF as a pair of pointers.  As such the
structure cannot be passed through a single register.  Diagnose such
cases in the frontend rather than trying to generate IR to perform this
operation.

Fixes: 59033

Differential Revision: https://reviews.llvm.org/D13851
Reviewed By: aaron.ballman

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -8845,6 +8845,9 @@ def warn_redefine_extname_not_applied : Warning<
 
 // inline asm.
 let CategoryName = "Inline Assembly Issue" in {
+  def err_asm_pmf_through_constraint_not_permitted
+    : Error<"cannot pass a pointer-to-member through register-constrained "
+            "inline assembly parameter">;
   def err_asm_invalid_lvalue_in_output : Error<"invalid lvalue in asm output">;
   def err_asm_invalid_output_constraint : Error<
     "invalid output constraint '%0' in asm">;

clang/lib/Sema/SemaStmtAsm.cpp

@@ -377,6 +377,11 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
 
     Expr *InputExpr = Exprs[i];
 
+    if (InputExpr->getType()->isMemberPointerType())
+      return StmtError(Diag(InputExpr->getBeginLoc(),
+                            diag::err_asm_pmf_through_constraint_not_permitted)
+                       << InputExpr->getSourceRange());
+
     // Referring to parameters is not allowed in naked functions.
     if (CheckNakedParmReference(InputExpr, *this))
       return StmtError();

clang/test/Sema/gnu-asm-pmf.cpp

@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-windows-msvc -std=c++2b -fsyntax-only %s -verify
+// RUN: %clang_cc1 -triple x86_64-unknown-windows-itanium -std=c++2b -fsyntax-only %s -verify
+
+struct S {
+  void operator()();
+};
+
+struct T {
+  virtual void operator()();
+};
+
+struct U {
+  static void operator()();
+};
+
+struct V: virtual T {
+  virtual void f();
+};
+
+struct W : virtual V {
+  int i;
+};
+
+struct X {
+  __UINTPTR_TYPE__ ptr;
+  __UINTPTR_TYPE__ adj;
+};
+
+auto L = [](){};
+
+void f() {
+  auto pmf = &S::operator();
+
+  __asm__ __volatile__ ("" : : "r"(&decltype(L)::operator()));
+  // expected-error@-1{{cannot pass a pointer-to-member through register-constrained inline assembly parameter}}
+  __asm__ __volatile__ ("" : : "r"(&S::operator()));
+  // expected-error@-1{{cannot pass a pointer-to-member through register-constrained inline assembly parameter}}
+  __asm__ __volatile__ ("" : : "r"(&T::operator()));
+  // expected-error@-1{{cannot pass a pointer-to-member through register-constrained inline assembly parameter}}
+  __asm__ __volatile__ ("" : : "r"(pmf));
+  // expected-error@-1{{cannot pass a pointer-to-member through register-constrained inline assembly parameter}}
+  __asm__ __volatile__ ("" : : "r"(&W::f));
+  // expected-error@-1{{cannot pass a pointer-to-member through register-constrained inline assembly parameter}}
+  __asm__ __volatile__ ("" : : "r"(&W::i));
+  // expected-error@-1{{cannot pass a pointer-to-member through register-constrained inline assembly parameter}}
+
+  __asm__ __volatile__ ("" : : "r"(X{0,0}));
+  __asm__ __volatile__ ("" : : "r"(&U::operator()));
+}