Diagnose CXX "this" reference in functions with naked attr

[weimingz]

Summary

Currently, clang will assert for non-static class member func with naked attribute because clang won't emit any prologues for such functions, so it would assert when it tries to codegen 'this' pointer

This patch fixes bug http://llvm.org/bugs/show_bug.cgi?id=22429

[rnk]

I think it would be preferable to extend the asm constraint checks to disallow CXXThisExpr.

[hans]

I think it would be preferable to extend the asm constraint checks to disallow CXXThisExpr.

Yes, I don't see why we would need to disallow naked member functions.

[weimingz]

In D7329#117184, @hans wrote:

I think it would be preferable to extend the asm constraint checks to disallow CXXThisExpr.

Yes, I don't see why we would need to disallow naked member functions.

Agree. Will do

[weimingz]

(undo unnecessary change made in previous patch)

[rnk]

lgtm

include/clang/Basic/DiagnosticSemaKinds.td

7178 ↗

(On Diff #19200)

We don't do smart backtick quotes like this.

[weimingz]

Hi Hans,

Are you OK with the patch?

Thanks,
Weiming

[hans]

Hi Hans,

Are you OK with the patch?

Yes, this looks good to me.

cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td

 def err_unknown_any_function : Error<
   "function %0 with unknown type must be given a function type">;
 
 def err_filter_expression_integral : Error<
   "filter expression type should be an integral value not %0">;
 
 def err_non_asm_stmt_in_naked_function : Error<
   "non-ASM statement in naked function is not supported">;
+def err_asm_naked_this_ref : Error<
+  "'this' pointer references not allowed in naked functions">;
 def err_asm_naked_parm_ref : Error<
   "parameter references not allowed in naked functions">;
 
 // OpenCL warnings and errors.
 def err_invalid_astype_of_different_size : Error<
   "invalid reinterpretation: sizes of %0 and %1 must match">;
 def err_static_kernel : Error<
   "kernel functions cannot be declared static">;

cfe/trunk/lib/Sema/SemaStmtAsm.cpp

 //===--- SemaStmtAsm.cpp - Semantic Analysis for Asm Statements -----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 //  This file implements semantic analysis for inline asm statements.
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/Sema/SemaInternal.h"
+#include "clang/AST/ExprCXX.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/Initialization.h"
 #include "clang/Sema/Lookup.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/ScopeInfo.h"
if (!Func)
     return false;
   if (!Func->hasAttr<NakedAttr>())
     return false;
 
   SmallVector<Expr*, 4> WorkList;
   WorkList.push_back(E);
   while (WorkList.size()) {
     Expr *E = WorkList.pop_back_val();
+    if (isa<CXXThisExpr>(E)) {
+      S.Diag(E->getLocStart(), diag::err_asm_naked_this_ref);
+      S.Diag(Func->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
+      return true;
+    }
     if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
       if (isa<ParmVarDecl>(DRE->getDecl())) {
         S.Diag(DRE->getLocStart(), diag::err_asm_naked_parm_ref);
         S.Diag(Func->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
         return true;
       }
     }
     for (Stmt *Child : E->children()) {

cfe/trunk/test/Sema/attr-naked.cpp

+// RUN: %clang_cc1 %s -verify -fsyntax-only -triple arm-none-linux
+class Foo {
+  void bar();
+  static void bar2();
+  unsigned v;
+  static unsigned s;
+};
+
+void __attribute__((naked)) Foo::bar() { // expected-note{{attribute is here}}
+  asm("mov r2, %0" : : "r"(v)); // expected-error{{'this' pointer references not allowed in naked functions}}
+}
+
+void __attribute__((naked)) Foo::bar2() {
+  asm("mov r2, %0" : : "r"(s)); // static member reference is OK
+}