[flang] Change vector always errors to warnings

flang/lib/Lower/Bridge.cpp

@@ -2607,9 +2607,6 @@ class FirConverter : public Fortran::lower::AbstractConverter {
 
     if (e->isA<Fortran::parser::NonLabelDoStmt>())
       e->dirs.push_back(&dir);
-    else
-      fir::emitFatalError(toLocation(),
-                          "loop directive must appear before a loop");
   }
 
   void genFIR(const Fortran::parser::CompilerDirective &dir) {

flang/lib/Semantics/canonicalize-directives.cpp

@@ -104,7 +104,7 @@ void CanonicalizationOfDirectives::CheckLoopDirective(
     std::string s{parser::ToUpperCaseLetters(dir.source.ToString())};
     s.pop_back(); // Remove trailing newline from source string
     messages_.Say(
-        dir.source, "A DO loop must follow the %s directive"_err_en_US, s);
+        dir.source, "A DO loop must follow the %s directive"_warn_en_US, s);
   }
 }
 

flang/test/Semantics/loop-directives.f90

@@ -1,19 +1,19 @@
-! RUN: %python %S/test_errors.py %s %flang
+! RUN: %python %S/test_errors.py %s %flang_fc1 -Werror
 
 subroutine empty
-  ! ERROR: A DO loop must follow the VECTOR ALWAYS directive
+  ! WARNING: A DO loop must follow the VECTOR ALWAYS directive
   !dir$ vector always
 end subroutine empty
 
 subroutine non_do
-  ! ERROR: A DO loop must follow the VECTOR ALWAYS directive
+  ! WARNING: A DO loop must follow the VECTOR ALWAYS directive
   !dir$ vector always
   a = 1
 end subroutine non_do
 
 subroutine execution_part
   do i=1,10
-  ! ERROR: A DO loop must follow the VECTOR ALWAYS directive
+  ! WARNING: A DO loop must follow the VECTOR ALWAYS directive
   !dir$ vector always
   end do
 end subroutine execution_part