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.

2 files changed, 64 insertions, 1 deletions

diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index 2cc2a18..6c1d6b3 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -13539,7 +13539,9 @@ 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 0000000..5e87139
--- /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;
+}