Revert "We allow implicit function declarations as an extension in all C dialects. Remove OpenCL special case."

Discussed on cfe-commits (Week-of-Mon-20180820), this change leads to
the generation of invalid IR for OpenCL without giving an error.
Therefore, the conclusion was to revert.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@342885 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -369,7 +369,7 @@ def warn_implicit_function_decl : Warning<
   "implicit declaration of function %0">,
   InGroup<ImplicitFunctionDeclare>, DefaultIgnore;
 def ext_implicit_function_decl : ExtWarn<
-  "implicit declaration of function %0 is invalid in %select{C99|OpenCL}1">,
+  "implicit declaration of function %0 is invalid in C99">,
   InGroup<ImplicitFunctionDeclare>;
 def note_function_suggestion : Note<"did you mean %0?">;
 
@@ -8556,6 +8556,8 @@ def err_opencl_scalar_type_rank_greater_than_vector_type : Error<
     "element. (%0 and %1)">;
 def err_bad_kernel_param_type : Error<
   "%0 cannot be used as the type of a kernel parameter">;
+def err_opencl_implicit_function_decl : Error<
+  "implicit declaration of function %0 is invalid in OpenCL">;
 def err_record_with_pointers_kernel_param : Error<
   "%select{struct|union}0 kernel parameters may not contain pointers">;
 def note_within_field_of_type : Note<

lib/Sema/SemaDecl.cpp

@@ -13360,15 +13360,17 @@ NamedDecl *Sema::ImplicitlyDefineFunction(SourceLocation Loc,
   }
 
   // Extension in C99.  Legal in C90, but warn about it.
-  // OpenCL v2.0 s6.9.u - Implicit function declaration is not supported.
   unsigned diag_id;
   if (II.getName().startswith("__builtin_"))
     diag_id = diag::warn_builtin_unknown;
-  else if (getLangOpts().C99 || getLangOpts().OpenCL)
+  // OpenCL v2.0 s6.9.u - Implicit function declaration is not supported.
+  else if (getLangOpts().OpenCL)
+    diag_id = diag::err_opencl_implicit_function_decl;
+  else if (getLangOpts().C99)
     diag_id = diag::ext_implicit_function_decl;
   else
     diag_id = diag::warn_implicit_function_decl;
-  Diag(Loc, diag_id) << &II << getLangOpts().OpenCL;
+  Diag(Loc, diag_id) << &II;
 
   // If we found a prior declaration of this function, don't bother building
   // another one. We've already pushed that one into scope, so there's nothing

test/SemaOpenCL/clang-builtin-version.cl

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -fblocks -verify -pedantic-errors -fsyntax-only -ferror-limit 100
+// RUN: %clang_cc1 %s -fblocks -verify -pedantic -fsyntax-only -ferror-limit 100
 
 // Confirm CL2.0 Clang builtins are not available in earlier versions
 

test/SemaOpenCL/to_addr_builtin.cl

@@ -10,7 +10,7 @@ void test(void) {
 
   glob = to_global(glob, loc);
 #if __OPENCL_C_VERSION__ < CL_VERSION_2_0
-  // expected-warning@-2{{implicit declaration of function 'to_global' is invalid in OpenCL}}
+  // expected-error@-2{{implicit declaration of function 'to_global' is invalid in OpenCL}}
   // expected-warning@-3{{incompatible integer to pointer conversion assigning to '__global int *' from 'int'}}
 #else
   // expected-error@-5{{invalid number of arguments to function: 'to_global'}}