OpenMP/Fortran: Fix loop-iter var privatization with !$OMP LOOP [PR108512]

For 'parallel', loop-iteration variables are marked are marked as 'private',
unless they either appear in an omp do/simd loop or an data-sharing clause
already exists for those on 'parallel'. 'omp loop' wasn't handled, leading
to (potentially) multiple data-sharing clauses in gfc_resolve_do_iterator
as omp_current_ctx pointed to the 'parallel' directive, ignoring the
in-betwen 'loop' directive.

The latter lead to a bogus diagnostic - or rather an ICE as the source
location var contained only '\0'.

gcc/fortran/ChangeLog:

	PR fortran/108512
	* openmp.cc (gfc_resolve_omp_do_blocks): Don't check 'inscan'
	restrictions for loop as rejected elsewhere.
	(gfc_resolve_do_iterator): Set a source location for added
	'private'-clause arguments.
	* resolve.cc (gfc_resolve_code): Call gfc_resolve_omp_do_blocks
	also for EXEC_OMP_LOOP.

gcc/testsuite/ChangeLog:

	PR fortran/108512
	* gfortran.dg/gomp/loop-5.f90: New test.

 gcc/fortran/openmp.cc                     |  5 +-
 gcc/fortran/resolve.cc                    |  1 +
 gcc/testsuite/gfortran.dg/gomp/loop-5.f90 | 84 +++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/openmp.cc b/gcc/fortran/openmp.cc
index cc1eab90b8c..7673a52249f 100644
--- a/gcc/fortran/openmp.cc
+++ b/gcc/fortran/openmp.cc
@@ -9056,7 +9056,9 @@ gfc_resolve_omp_do_blocks (gfc_code *code, gfc_namespace *ns)
 	}
       if (i < omp_current_do_collapse || omp_current_do_collapse <= 0)
 	omp_current_do_collapse = 1;
-      if (code->ext.omp_clauses->lists[OMP_LIST_REDUCTION_INSCAN])
+      if (code->op == EXEC_OMP_LOOP)
+	;  /* Already rejected in resolve_omp_clauses.  */
+      else if (code->ext.omp_clauses->lists[OMP_LIST_REDUCTION_INSCAN])
 	{
 	  locus *loc
 	    = &code->ext.omp_clauses->lists[OMP_LIST_REDUCTION_INSCAN]->where;
@@ -9224,6 +9226,7 @@ gfc_resolve_do_iterator (gfc_code *code, gfc_symbol *sym, bool add_clause)
 
       p = gfc_get_omp_namelist ();
       p->sym = sym;
+      p->where = omp_current_ctx->code->loc;
       p->next = omp_clauses->lists[OMP_LIST_PRIVATE];
       omp_clauses->lists[OMP_LIST_PRIVATE] = p;
     }
diff --git a/gcc/fortran/resolve.cc b/gcc/fortran/resolve.cc
index 94213cd3cd4..bd2a749776d 100644
--- a/gcc/fortran/resolve.cc
+++ b/gcc/fortran/resolve.cc
@@ -11950,6 +11950,7 @@ gfc_resolve_code (gfc_code *code, gfc_namespace *ns)
 	    case EXEC_OMP_DISTRIBUTE_SIMD:
 	    case EXEC_OMP_DO:
 	    case EXEC_OMP_DO_SIMD:
+	    case EXEC_OMP_LOOP:
 	    case EXEC_OMP_SIMD:
 	    case EXEC_OMP_TARGET_SIMD:
 	      gfc_resolve_omp_do_blocks (code, ns);
diff --git a/gcc/testsuite/gfortran.dg/gomp/loop-5.f90 b/gcc/testsuite/gfortran.dg/gomp/loop-5.f90
new file mode 100644
index 00000000000..1948e782653
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/loop-5.f90
@@ -0,0 +1,84 @@
+! { dg-additional-options "-fdump-tree-original" }
+!
+! PR fortran/108512
+
+! The problem was that the context wasn't reset for the 'LOOP'
+! such that the clauses of the loops weren't seen when adding
+! PRIVATE clauses.
+!
+! In the following, only the loop variable of the non-OpenMP loop
+! in 'subroutine four' should get a front-end addded PRIVATE clause
+
+implicit none
+integer :: x, a(10), b(10), n
+    n = 10
+    a = -42
+    b = [(2*x, x=1,10)]
+
+! { dg-final { scan-tree-dump-times "#pragma omp target map\\(tofrom:a\\) map\\(tofrom:b\\) map\\(tofrom:x\\)\[\r\n\]" 1 "original" } }
+! { dg-final { scan-tree-dump-times "#pragma omp parallel\[\r\n\]" 2 "original" } }
+!  ^- shows up twice; checked only here.
+! { dg-final { scan-tree-dump-times "#pragma omp loop lastprivate\\(x\\)\[\r\n\]" 1 "original" } }
+
+    !$omp target parallel map(tofrom: a, b, x)
+    !$omp loop lastprivate(x)
+    DO x = 1, n
+      a(x) = a(x) + b(x)
+    END DO
+    !$omp end loop
+    !$omp end target parallel
+    if (x /= 11) error stop
+    if (any (a /= [(2*x - 42, x=1,10)])) error stop
+    call two()
+    call three()
+    call four()
+end
+
+subroutine two
+  implicit none
+  integer :: ii, mm, arr(10)
+  mm = 10
+  arr = 0
+
+! { dg-final { scan-tree-dump-times "#pragma omp target map\\(tofrom:arr\\) map\\(tofrom:ii\\)\[\r\n\]" 1 "original" } }
+! { dg-final { scan-tree-dump-times "#pragma omp parallel shared\\(ii\\)\[\r\n\]" 1 "original" } }
+! { dg-final { scan-tree-dump-times "#pragma omp loop lastprivate\\(ii\\)\[\r\n\]" 1 "original" } }
+
+  !$omp target parallel loop map(tofrom: arr) lastprivate(ii)
+    DO ii = 1, mm
+      arr(ii) = arr(ii) + ii
+    END DO
+end
+
+subroutine three
+  implicit none
+  integer :: kk, zz, var(10)
+  zz = 10
+  var = 0
+
+! { dg-final { scan-tree-dump-times "#pragma omp target map\\(tofrom:var\\)\[\r\n\]" 1 "original" } }
+! "#pragma omp parallel\[\r\n\]" - shows up twice, dump checked above
+! { dg-final { scan-tree-dump-times "#pragma omp loop\[\r\n\]" 1 "original" } }
+
+  !$omp target parallel loop map(tofrom: var)
+    DO kk = 1, zz
+      var(kk) = var(kk) + kk
+    END DO
+end
+
+subroutine four
+  implicit none
+  integer :: jj, qq, dist(10)
+  qq = 10
+  dist = 0
+
+! { dg-final { scan-tree-dump-times "#pragma omp target map\\(tofrom:dist\\)\[\r\n\]" 1 "original" } }
+! { dg-final { scan-tree-dump-times "#pragma omp parallel private\\(jj\\)\[\r\n\]" 1 "original" } }
+
+  !$omp target parallel map(tofrom: dist)
+    ! *no* '!$omp do/loop/simd'
+    DO jj = 1, qq
+      dist(qq) = dist(qq) + qq
+    END DO
+  !$omp end target parallel
+end