[clang][OpenMP] Fix declare simd use on in-class member template function

[mikerice]

Summary

Return the Decl when parsing the template member declaration so the
'omp declare simd' pragma can be applied to it. Previously a nullptr
was returned causing an error applying the pragma.

Fixes #52700.

The return of nullptr here seems to have been in the compiler for quite a long time.
I wasn't able to determine if that was intentional.

[ABataev]

clang/lib/Parse/ParseTemplate.cpp

205

Can we have more than a single decl here?

[mikerice]

clang/lib/Parse/ParseTemplate.cpp

205

It is possible for ParseCXXClassMemberDeclaration to return multiple declarations in this context. For example:

struct A {                            
  #pragma omp declare simd linear(a:X)
  template<int X, typename T>         
  T infunc1(T a), infunc2(T a);       
};

But this code is only setup to return one Decl.

Since the 'declare simd' code expects only one Decl as well, it is probably best to just return the Decl when there is just one. Then an error will still occur trying to process the declare simd in case of code like above.

[mikerice]

Return Decl only when a single Decl.
Test that error is still given if multiple Decls.

[ABataev]

LG

clang/lib/Parse/ParseTemplate.cpp

if (Tok.is(tok::kw_static_assert)) {
     Diag(Tok.getLocation(), diag::err_templated_invalid_declaration)
       << TemplateInfo.getSourceRange();
     // Parse the static_assert declaration to improve error recovery.
     return ParseStaticAssertDeclaration(DeclEnd);
   }
 
   if (Context == DeclaratorContext::Member) {
     // We are parsing a member template.
-    ParseCXXClassMemberDeclaration(AS, AccessAttrs, TemplateInfo,
-                                   &DiagsFromTParams);
+    DeclGroupPtrTy D = ParseCXXClassMemberDeclaration(
+        AS, AccessAttrs, TemplateInfo, &DiagsFromTParams);
+
+    if (!D || !D.get().isSingleDecl())
       return nullptr;
+    return D.get().getSingleDecl();
   }
 
   ParsedAttributes prefixAttrs(AttrFactory);
   MaybeParseCXX11Attributes(prefixAttrs);
 
   if (Tok.is(tok::kw_using)) {
     auto usingDeclPtr = ParseUsingDirectiveOrDeclaration(Context, TemplateInfo, DeclEnd,
                                                          prefixAttrs);

clang/test/OpenMP/declare_simd_codegen.cpp

void f(int (&g)[]) {
   int res = t16.tadd(b);
   int c[64];
   vv.add(res, res);
   vv.taddpf(p, p);
   vv.tadd(g, res);
   foo(c, p);
 }
 
+struct A {
+  #pragma omp declare simd linear(a:X)
+  template<int X, typename T>
+  T infunc(T a) { return a * 2; }
+
+  template<int Y, typename U>
+  U outfunc(U *a);
+};
+
+#pragma omp declare simd linear(a:Y)
+template<int Y, typename U>
+U A::outfunc(U *a) { return *a * 2; }
+
+void test_member_template()
+{
+  struct A a;
+  int i = 32;
+  float f = 1.0;
+  int t = a.infunc<8, int>(i);
+  float u = a.outfunc<4, float>(&f);
+}
+
 #pragma omp declare simd
 #pragma omp declare simd notinbranch aligned(a : 32)
 int bar(VV v, float *a) { return 0; }
 #pragma omp declare simd
 #pragma omp declare simd notinbranch aligned(a)
 float baz(VV v, int a[]) { return 0; }
 #pragma omp declare simd
 #pragma omp declare simd notinbranch aligned(a)

 // CHECK-DAG: define {{.+}}@_Z1hIfEvPT_S1_S1_S1_(
 // CHECK-DAG: define {{.+}}@_ZN2VV3addEii(
 // CHECK-DAG: define {{.+}}@_ZN2VV6taddpfEPfRS0_(
 // CHECK-DAG: define {{.+}}@_ZN2VV4taddERA_iRi(
 // CHECK-DAG: define {{.+}}@_Z1fRA_i(
 // CHECK-DAG: define {{.+}}@_ZN3TVVILi16EfE6taddpfEPfRS1_(
 // CHECK-DAG: define {{.+}}@_ZN3TVVILi16EfE4taddEi(
 // CHECK-DAG: define {{.+}}@_Z3fooILi64EEvRAT__iRPf(
+// CHECK-DAG: define {{.+}}@_ZN1A6infuncILi8EiEET0_S1_
+// CHECK-DAG: define {{.+}}@_ZN1A7outfuncILi4EfEET0_PS1_
 // CHECK-DAG: define {{.+}}@_Z3bar2VVPf(
 // CHECK-DAG: define {{.+}}@_Z3baz2VVPi(
 // CHECK-DAG: define {{.+}}@_Z3bay2VVRPd(
 // CHECK-DAG: define {{.+}}@_Z3bax2VVPdi(
 // CHECK-DAG: define {{.+}}@_Z3fooPffi(
 // CHECK-DAG: define {{.+}}@_Z3food(
 // CHECK-DAG: declare {{.+}}@_Z5add_2Pf(
 // CHECK-DAG: define {{.+}}@_Z11constlineari(

 // CHECK-DAG: "_ZGVbN64va128U64__Z3fooILi64EEvRAT__iRPf"
 // CHECK-DAG: "_ZGVcM64va128U64__Z3fooILi64EEvRAT__iRPf"
 // CHECK-DAG: "_ZGVcN64va128U64__Z3fooILi64EEvRAT__iRPf"
 // CHECK-DAG: "_ZGVdM64va128U64__Z3fooILi64EEvRAT__iRPf"
 // CHECK-DAG: "_ZGVdN64va128U64__Z3fooILi64EEvRAT__iRPf"
 // CHECK-DAG: "_ZGVeM64va128U64__Z3fooILi64EEvRAT__iRPf"
 // CHECK-DAG: "_ZGVeN64va128U64__Z3fooILi64EEvRAT__iRPf"
 
+// CHECK-DAG: "_ZGVbM4vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVbN4vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVcM8vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVcN8vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVdM8vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVdN8vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVeM16vl8__ZN1A6infuncILi8EiEET0_S1_"
+// CHECK-DAG: "_ZGVeN16vl8__ZN1A6infuncILi8EiEET0_S1_"
+
+// CHECK-DAG: "_ZGVbM4vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVbN4vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVcM8vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVcN8vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVdM8vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVdN8vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVeM16vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+// CHECK-DAG: "_ZGVeN16vl16__ZN1A7outfuncILi4EfEET0_PS1_"
+
 // CHECK-DAG: "_ZGVbM4vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVbN4vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVcM8vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVcN8vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVdM8vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVdN8vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVeM16vv__Z3bar2VVPf"
 // CHECK-DAG: "_ZGVeN16vv__Z3bar2VVPf"

clang/test/OpenMP/declare_simd_messages.cpp

 
 // expected-error@+3 {{function declaration is expected after 'declare simd' directive}}
 // expected-error@+1 {{function declaration is expected after 'declare simd' directive}}
 #pragma omp declare simd
 #pragma omp declare simd
 #pragma init_seg(compiler)
 int main();
 
+struct A {
+// expected-error@+1 {{function declaration is expected after 'declare simd' directive}}
+  #pragma omp declare simd
+  template<typename T>
+  T infunc1(T a), infunc2(T a);
+};
+
 // expected-error@+1 {{single declaration is expected after 'declare simd' directive}}
 #pragma omp declare simd
 // expected-note@+1 {{declared here}}
 int b, c;
 
 // expected-error@+1 {{'C' does not refer to a value}}
 #pragma omp declare simd simdlen(C)
 // expected-note@+1 {{declared here}}