Fortran:Fix simplification of constructors with implied-do [PR98458]

2021-01-08  Paul Thomas  <pault@gcc.gnu.org>

gcc/fortran
	PR fortran/98458
	* simplify.c (is_constant_array_expr): If an array constructor
	expression has elements other than constants or structures, try
	fixing the expression with gfc_reduce_init_expr. Also, if shape
	is NULL, obtain the array size and set it.

gcc/testsuite/
	PR fortran/98458
	* gfortran.dg/implied_do_3.f90 : New test.

1 files changed, 33 insertions, 1 deletions

diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index dac48a8..23317a2 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -220,6 +220,8 @@ static bool
 is_constant_array_expr (gfc_expr *e)
 {
   gfc_constructor *c;
+  bool array_OK = true;
+  mpz_t size;
 
   if (e == NULL)
     return true;
@@ -235,9 +237,39 @@ is_constant_array_expr (gfc_expr *e)
        c; c = gfc_constructor_next (c))
     if (c->expr->expr_type != EXPR_CONSTANT
 	  && c->expr->expr_type != EXPR_STRUCTURE)
+      {
+	array_OK = false;
+	break;
+      }
+
+  /* Check and expand the constructor.  */
+  if (!array_OK && gfc_init_expr_flag && e->rank == 1)
+    {
+      array_OK = gfc_reduce_init_expr (e);
+      /* gfc_reduce_init_expr resets the flag.  */
+      gfc_init_expr_flag = true;
+    }
+  else
+    return array_OK;
+
+  /* Recheck to make sure that any EXPR_ARRAYs have gone.  */
+  for (c = gfc_constructor_first (e->value.constructor);
+       c; c = gfc_constructor_next (c))
+    if (c->expr->expr_type != EXPR_CONSTANT
+	  && c->expr->expr_type != EXPR_STRUCTURE)
       return false;
 
-  return true;
+  /* Make sure that the array has a valid shape.  */
+  if (e->shape == NULL && e->rank == 1)
+    {
+      if (!gfc_array_size(e, &size))
+	return false;
+      e->shape = gfc_get_shape (1);
+      mpz_init_set (e->shape[0], size);
+      mpz_clear (size);
+    }
+
+  return array_OK;
 }
 
 /* Test for a size zero array.  */