[OpenMP] Fix a crash on invalid with unroll partial (#139280)

You cannot get the integer constant expression's value if the expression
contains errors.

Fixes https://github.com/llvm/llvm-project/issues/139267

clang/docs/ReleaseNotes.rst

@@ -905,6 +905,8 @@ OpenMP Support
 - Added support 'no_openmp_constructs' assumption clause.
 - Added support for 'self_maps' in map and requirement clause.
 - Added support for 'omp stripe' directive.
+- Fixed a crashing bug with ``omp unroll partial`` if the argument to
+  ``partial`` was an invalid expression. (#GH139267)
 - Fixed a crashing bug with ``omp tile sizes`` if the argument to ``sizes`` was
   an invalid expression. (#GH139073)
 - Fixed a crashing bug with ``omp distribute dist_schedule`` if the argument to

clang/lib/Sema/SemaOpenMP.cpp

@@ -14912,7 +14912,8 @@ StmtResult SemaOpenMP::ActOnOpenMPUnrollDirective(ArrayRef<OMPClause *> Clauses,
   // Determine the unroll factor.
   uint64_t Factor;
   SourceLocation FactorLoc;
-  if (Expr *FactorVal = PartialClause->getFactor()) {
+  if (Expr *FactorVal = PartialClause->getFactor();
+      FactorVal && !FactorVal->containsErrors()) {
     Factor = FactorVal->getIntegerConstantExpr(Context)->getZExtValue();
     FactorLoc = FactorVal->getExprLoc();
   } else {

clang/test/OpenMP/unroll_messages.cpp

@@ -128,3 +128,12 @@ void template_inst(int n) {
   // expected-note@+1 {{in instantiation of function template specialization 'templated_func<int, -1>' requested here}}
   templated_func<int, -1>(n);
 }
+
+namespace GH139267 {
+void f(void) {
+  // This would previously crash with follow-on recovery after issuing the error.
+#pragma omp unroll partial(a) // expected-error {{use of undeclared identifier 'a'}}
+  for (int i = 0; i < 10; i++)
+    ;
+}
+}