[gcc r11-8643] openmp: Fix up *_reduction clause handling with UDRs on PARM_DECLs [PR101167]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:f50a222dffb448ef5c69a64b6945acafc6b16e12

commit r11-8643-gf50a222dffb448ef5c69a64b6945acafc6b16e12
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Jun 23 10:03:28 2021 +0200

    openmp: Fix up *_reduction clause handling with UDRs on PARM_DECLs [PR101167]
    
    The following testcase FAILs, because the UDR combiner is invoked incorrectly.
    lower_omp_rec_clauses expects that when it sets
    DECL_VALUE_EXPR/DECL_HAS_VALUE_EXPR_P
    for both the placeholder and the var that everything will be properly
    regimplified, but as the variable in question is a PARM_DECL rather than
    VAR_DECL, lower_omp_regimplify_p doesn't say that it should be regimplified
    and so it is not.
    
    2021-06-23  Jakub Jelinek  <jakub@redhat.com>
    
            PR middle-end/101167
            * omp-low.c (lower_omp_regimplify_p): Regimplify also PARM_DECLs
            and RESULT_DECLs that have DECL_HAS_VALUE_EXPR_P set.
    
            * testsuite/libgomp.c-c++-common/task-reduction-15.c: New test.
    
    (cherry picked from commit 679506c3830ea1a93c755413609bfac3538e2cbd)

Diff:
---
 gcc/omp-low.c                                      |  4 +-
 .../libgomp.c-c++-common/task-reduction-15.c       | 61 ++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index 0817ee7091a..acea2148b27 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -13164,7 +13164,9 @@ lower_omp_regimplify_p (tree *tp, int *walk_subtrees,
   tree t = *tp;
 
   /* Any variable with DECL_VALUE_EXPR needs to be regimplified.  */
-  if (VAR_P (t) && data == NULL && DECL_HAS_VALUE_EXPR_P (t))
+  if ((VAR_P (t) || TREE_CODE (t) == PARM_DECL || TREE_CODE (t) == RESULT_DECL)
+      && data == NULL
+      && DECL_HAS_VALUE_EXPR_P (t))
     return t;
 
   if (task_shared_vars
diff --git a/libgomp/testsuite/libgomp.c-c++-common/task-reduction-15.c b/libgomp/testsuite/libgomp.c-c++-common/task-reduction-15.c
new file mode 100644
index 00000000000..5e87139ccfb
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/task-reduction-15.c
@@ -0,0 +1,61 @@
+/* PR middle-end/101167 */
+
+extern
+#ifdef __cplusplus
+"C"
+#endif
+void abort (void);
+
+struct S { int a, b, c[2]; };
+
+void
+init (struct S *x)
+{
+  x->a = 0;
+  x->b = 0;
+  x->c[0] = 0;
+  x->c[1] = 0;
+}
+
+void
+merge (struct S *x, struct S *y)
+{
+  x->a += y->a;
+  x->b += y->b;
+}
+
+#pragma omp declare reduction (+: struct S : merge (&omp_out, &omp_in)) initializer (init (&omp_priv))
+
+void
+foo (struct S x)
+{
+  #pragma omp taskgroup task_reduction (+: x)
+  {
+    #pragma omp task in_reduction (+: x)
+    {
+      x.a++;
+      x.b++;
+    }
+    #pragma omp task in_reduction (+: x)
+    {
+      x.a += 4;
+      x.b += 14;
+    }
+    #pragma omp task in_reduction (+: x)
+    {
+      x.a += 9;
+      x.b += 19;
+    }
+  }
+  if (x.a != 56 || x.b != 86)
+    abort ();
+}
+
+int
+main ()
+{
+  struct S x = { 42, 52 };
+  #pragma omp parallel master num_threads(3)
+  foo (x);
+  return 0;
+}