[PATCH] AST: Mangle nullptr properly in template args for the Itanium ABI

[Richard Smith]

On 7 Sep 2013 02:39, "David Majnemer" <david.majnemer at gmail.com> wrote:
>
> Hi rsmith, rjmccall, eli.friedman, doug.gregor,
>
> We would previously treat nullptr literals as we were mangling the for
> the null pointer value of the template parameter's type instead.
>
> This fixes PR17141.
>
> http://llvm-reviews.chandlerc.com/D1625
>
> Files:
>   lib/AST/ItaniumMangle.cpp
>   test/CodeGenCXX/mangle-nullptr-arg.cpp
>   test/CodeGenCXX/visibility.cpp
>
> Index: lib/AST/ItaniumMangle.cpp
> ===================================================================
> --- lib/AST/ItaniumMangle.cpp
> +++ lib/AST/ItaniumMangle.cpp
> @@ -3337,10 +3337,8 @@
>      break;
>    }
>    case TemplateArgument::NullPtr: {
> -    //  <expr-primary> ::= L <type> 0 E
> -    Out << 'L';
> -    mangleType(A.getNullPtrType());
> -    Out << "0E";
> +    //  <expr-primary> ::= L <nullptr type> E
> +    Out << "LDnE";
>      break;
>    }
>    case TemplateArgument::Pack: {
> Index: test/CodeGenCXX/mangle-nullptr-arg.cpp
> ===================================================================
> --- test/CodeGenCXX/mangle-nullptr-arg.cpp
> +++ test/CodeGenCXX/mangle-nullptr-arg.cpp
> @@ -2,15 +2,15 @@
>
>  template<int *ip> struct IP {};
>
> -// CHECK-LABEL: define void @_Z5test12IPILPi0EE
> +// CHECK-LABEL: define void @_Z5test12IPILDnEE
>  void test1(IP<nullptr>) {}

The old mangling was correct here.

>  struct X{ };
>  template<int X::*pm> struct PM {};
>
> -// CHECK-LABEL: define void @_Z5test22PMILM1Xi0EE
> +// CHECK-LABEL: define void @_Z5test22PMILDnEE
>  void test2(PM<nullptr>) { }

And here. You should only change the mangling of a null pointer of type
std::nullptr_t.

Also, maybe this ABI break should be listed in the release notes. Does GCC
implement this rule yet?

> -// CHECK-LABEL: define void @_Z5test316DependentTypePtrIPiLS0_0EE
> +// CHECK-LABEL: define void @_Z5test316DependentTypePtrIPiLDnEE
>  template<typename T, T x> struct DependentTypePtr {};
>  void test3(DependentTypePtr<int*,nullptr>) { }
> Index: test/CodeGenCXX/visibility.cpp
> ===================================================================
> --- test/CodeGenCXX/visibility.cpp
> +++ test/CodeGenCXX/visibility.cpp
> @@ -971,8 +971,8 @@
>    void f() {
>      zed<nullptr>();
>    }
> -  // CHECK-LABEL: define internal void
@_ZN6test523zedILPNS_12_GLOBAL__N_13fooE0EEEvv
> -  // CHECK-HIDDEN-LABEL: define internal void
@_ZN6test523zedILPNS_12_GLOBAL__N_13fooE0EEEvv
> +  // CHECK-LABEL: define internal void @_ZN6test523zedILDnEEEvv
> +  // CHECK-HIDDEN-LABEL: define internal void @_ZN6test523zedILDnEEEvv
>  }
>
>  namespace test53 {
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