[Sema][SVE] Don't allow static or thread-local variables to have sizeless type

[rsandifo-arm]

Summary

clang accepts a TU containing just:

__SVInt8_t x;

However, sizeless types are not allowed to have static or thread-local
storage duration and trying to code-generate the TU triggers an LLVM
fatal error:

Globals cannot contain scalable vectors
<vscale x 16 x i8>* @x
fatal error: error in backend: Broken module found, compilation aborted!

This patch adds an associated clang diagnostic.

[efriedma]

LGTM

clang/include/clang/Basic/DiagnosticSemaKinds.td

def note_carries_dependency_missing_first_decl : Note<
   "declaration missing '[[carries_dependency]]' attribute is here">;
 def err_carries_dependency_param_not_function_decl : Error<
   "'[[carries_dependency]]' attribute only allowed on parameter in a function "
   "declaration or lambda">;
 def err_block_on_nonlocal : Error<
   "__block attribute not allowed, only allowed on local variables">;
 def err_block_on_vm : Error<
   "__block attribute not allowed on declaration with a variably modified type">;
+def err_sizeless_nonlocal : Error<
+  "non-local variable with sizeless type %0">;
 
 def err_vec_builtin_non_vector : Error<
  "first two arguments to %0 must be vectors">;
 def err_vec_builtin_incompatible_vector : Error<
   "first two arguments to %0 must have the same type">;
 def err_vsx_builtin_nonconstant_argument : Error<
   "argument %0 to %1 must be a 2-bit unsigned literal (i.e. 0, 1, 2 or 3)">;
 

clang/lib/Sema/SemaDecl.cpp

void Sema::CheckVariableDeclarationType(VarDecl *NewVD) {
   }
 
   if (!NewVD->hasLocalStorage() && NewVD->hasAttr<BlocksAttr>()) {
     Diag(NewVD->getLocation(), diag::err_block_on_nonlocal);
     NewVD->setInvalidDecl();
     return;
   }
 
+  if (!NewVD->hasLocalStorage() && T->isSizelessType()) {
+    Diag(NewVD->getLocation(), diag::err_sizeless_nonlocal) << T;
+    NewVD->setInvalidDecl();
+    return;
+  }
+
   if (isVM && NewVD->hasAttr<BlocksAttr>()) {
     Diag(NewVD->getLocation(), diag::err_block_on_vm);
     NewVD->setInvalidDecl();
     return;
   }
 
   if (NewVD->isConstexpr() && !T->isDependentType() &&
       RequireLiteralType(NewVD->getLocation(), T,

clang/test/Sema/sizeless-1.c

 // RUN: %clang_cc1 -fsyntax-only -verify -Wall -W -Wno-comment -triple arm64-linux-gnu -target-feature +sve -std=c90 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -Wall -W -triple arm64-linux-gnu -target-feature +sve -std=c11 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -Wall -W -triple arm64-linux-gnu -target-feature +sve -std=gnu11 %s
 
 typedef __SVInt8_t svint8_t;
 typedef __SVInt16_t svint16_t;
 
+svint8_t global_int8;          // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+extern svint8_t extern_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+static svint8_t static_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+__thread svint8_t thread_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
 svint8_t *global_int8_ptr;
 extern svint8_t *extern_int8_ptr;
 static svint8_t *static_int8_ptr;
 
 typedef svint8_t int8_typedef;
 typedef svint8_t *int8_ptr_typedef;
 
 int sizeof_int8 = sizeof(svint8_t);             // expected-error {{invalid application of 'sizeof' to sizeless type 'svint8_t'}}

 
 void unused() {
   svint8_t unused_int8; // expected-warning {{unused}}
 }
 
 struct incomplete_struct *incomplete_ptr;
 
 void func(int sel) {
+  static svint8_t static_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+
   svint8_t local_int8;
   svint16_t local_int16;
 
   svint8_t __attribute__((aligned)) aligned_int8_1;    // expected-error {{'aligned' attribute cannot be applied to sizeless type 'svint8_t'}}
   svint8_t __attribute__((aligned(4))) aligned_int8_2; // expected-error {{'aligned' attribute cannot be applied to sizeless type 'svint8_t'}}
   svint8_t _Alignas(int) aligned_int8_3;               // expected-error {{'_Alignas' attribute cannot be applied to sizeless type 'svint8_t'}}
 
   int _Alignas(svint8_t) aligned_int; // expected-error {{invalid application of 'alignof' to sizeless type 'svint8_t'}}

clang/test/SemaCXX/sizeless-1.cpp

 // RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -verify -W -Wall -Wrange-loop-analysis -triple arm64-linux-gnu -target-feature +sve -std=c++98 %s
 // RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -verify -W -Wall -Wrange-loop-analysis -triple arm64-linux-gnu -target-feature +sve -std=c++11 %s
 // RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -verify -W -Wall -Wrange-loop-analysis -triple arm64-linux-gnu -target-feature +sve -std=c++17 %s
 // RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -verify -W -Wall -Wrange-loop-analysis -triple arm64-linux-gnu -target-feature +sve -std=gnu++17 %s
 
 namespace std {
 struct type_info;
 }
 
 typedef __SVInt8_t svint8_t;
 typedef __SVInt16_t svint16_t;
 
+svint8_t global_int8;          // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+extern svint8_t extern_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+static svint8_t static_int8;   // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+__thread svint8_t thread_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
 svint8_t *global_int8_ptr;
 extern svint8_t *extern_int8_ptr;
 static svint8_t *static_int8_ptr;
 
 typedef svint8_t int8_typedef;
 typedef svint8_t *int8_ptr_typedef;
 
 int sizeof_int8 = sizeof(svint8_t);             // expected-error {{invalid application of 'sizeof' to sizeless type 'svint8_t'}}

 
 void unused() {
   svint8_t unused_int8; // expected-warning {{unused}}
 }
 
 struct incomplete_struct *incomplete_ptr;
 
 void func(int sel) {
+  static svint8_t static_int8; // expected-error {{non-local variable with sizeless type 'svint8_t'}}
+
   svint8_t local_int8;
   svint16_t local_int16;
 
   svint8_t __attribute__((aligned)) aligned_int8_1;    // expected-error {{'aligned' attribute cannot be applied to sizeless type 'svint8_t'}}
   svint8_t __attribute__((aligned(4))) aligned_int8_2; // expected-error {{'aligned' attribute cannot be applied to sizeless type 'svint8_t'}}
   svint8_t _Alignas(int) aligned_int8_3;               // expected-error {{'_Alignas' attribute cannot be applied to sizeless type 'svint8_t'}}
 
   int _Alignas(svint8_t) aligned_int; // expected-error {{invalid application of 'alignof' to sizeless type 'svint8_t'}}