[OpenMP] fix seg-faults printing diagnostics with invalid ordered(n) values

[rcraik]

Summary

When the value specified for n in ordered(n) is larger than the number of loops a segmentation fault can occur in one of two ways when attempting to print out a diagnostic for an associated depend(sink : vec):

1. The iteration vector vec contains less than n items
2. The iteration vector vec contains a variable that is not a loop control variable

This patch addresses both of these issues.

[ABataev]

LG

include/clang/Basic/DiagnosticSemaKinds.td

def err_omp_critical_with_hint : Error<
   "constructs with the same name must have a 'hint' clause with the same value">;
 def note_omp_critical_hint_here : Note<
   "%select{|previous }0'hint' clause with value '%1'">;
 def note_omp_critical_no_hint : Note<
   "%select{|previous }0directive with no 'hint' clause specified">;
 def err_omp_depend_clause_thread_simd : Error<
   "'depend' clauses cannot be mixed with '%0' clause">;
 def err_omp_depend_sink_expected_loop_iteration : Error<
-  "expected %0 loop iteration variable">;
+  "expected%select{| %1}0 loop iteration variable">;
 def err_omp_depend_sink_unexpected_expr : Error<
   "unexpected expression: number of expressions is larger than the number of associated loops">;
 def err_omp_depend_sink_expected_plus_minus : Error<
   "expected '+' or '-' operation">;
 def err_omp_depend_sink_source_not_allowed : Error<
   "'depend(%select{source|sink:vec}0)' clause%select{|s}0 cannot be mixed with 'depend(%select{sink:vec|source}0)' clause%select{s|}0">;
 def err_omp_linear_ordered : Error<
   "'linear' clause cannot be specified along with 'ordered' clause with a parameter">;

lib/Sema/SemaOpenMP.cpp

for (auto &RefExpr : VarList) {
           ExprResult RHSRes = VerifyPositiveIntegerConstantInClause(
               RHS, OMPC_depend, /*StrictlyPositive=*/false);
           if (RHSRes.isInvalid())
             continue;
         }
         if (!CurContext->isDependentContext() &&
             DSAStack->getParentOrderedRegionParam() &&
             DepCounter != DSAStack->isParentLoopControlVariable(D).first) {
-          Diag(ELoc, diag::err_omp_depend_sink_expected_loop_iteration)
-              << DSAStack->getParentLoopControlVariable(
-                     DepCounter.getZExtValue());
+          ValueDecl* VD = DSAStack->getParentLoopControlVariable(
+          if (VD) {
+            Diag(ELoc, diag::err_omp_depend_sink_expected_loop_iteration)
+                << 1 << VD;
+          } else {
+             Diag(ELoc, diag::err_omp_depend_sink_expected_loop_iteration) << 0;
+          }
           continue;
         }
         OpsOffs.push_back({RHS, OOK});
       } else {
         auto *ASE = dyn_cast<ArraySubscriptExpr>(SimpleExpr);
         if (!RefExpr->IgnoreParenImpCasts()->isLValue() ||
             (ASE &&
              !ASE->getBase()
for (auto &RefExpr : VarList) {
           continue;
         }
       }
       Vars.push_back(RefExpr->IgnoreParenImpCasts());
     }
 
     if (!CurContext->isDependentContext() && DepKind == OMPC_DEPEND_sink &&
         TotalDepCount > VarList.size() &&
-        DSAStack->getParentOrderedRegionParam()) {
-      Diag(EndLoc, diag::err_omp_depend_sink_expected_loop_iteration)
+        DSAStack->getParentOrderedRegionParam() &&
+        DSAStack->getParentLoopControlVariable(VarList.size() + 1)) {
+      Diag(EndLoc, diag::err_omp_depend_sink_expected_loop_iteration) << 1
           << DSAStack->getParentLoopControlVariable(VarList.size() + 1);
     }
     if (DepKind != OMPC_DEPEND_source && DepKind != OMPC_DEPEND_sink &&
         Vars.empty())
       return nullptr;
   }
   auto *C = OMPDependClause::Create(Context, StartLoc, LParenLoc, EndLoc,
                                     DepKind, DepLoc, ColonLoc, Vars);

test/OpenMP/ordered_messages.cpp

 #endif
 #pragma omp ordered depend(sink : i*0, j-4)// expected-error {{expected '+' or '-' operation}}
 #pragma omp ordered depend(sink : i-0, j+sizeof(int)) depend(sink : i-0, j+sizeof(int))
 #pragma omp ordered depend(sink : i-0, j+sizeof(int)) depend(source) // expected-error {{'depend(source)' clause cannot be mixed with 'depend(sink:vec)' clauses}}
 #pragma omp ordered depend(source) depend(sink : i-0, j+sizeof(int)) // expected-error {{'depend(sink:vec)' clauses cannot be mixed with 'depend(source)' clause}}
     }
   }
 
+#pragma omp for ordered(2) // expected-note {{as specified in 'ordered' clause}}
+  for (int i = 0; i < 10; ++i) { // expected-error {{expected 2 for loops after '#pragma omp for', but found only 1}}
+#pragma omp ordered depend(sink : i)
+    int j;
+#pragma omp ordered depend(sink : i, j) // expected-error {{expected loop iteration variable}}
+    foo();
+  }
+
   return foo<int>(); // expected-note {{in instantiation of function template specialization 'foo<int>' requested here}}
 }