re PR fortran/71902 (Unneeded temporary on reallocatable character assignment)

2016-09-04  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/71902
	* frontend-passes.c (realloc_string_callback): Also check for the
	lhs being deferred.  Name temporary variable "realloc_string".

2016-09-04  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/71902
	* gfortran.dg/dependency_47.f90:  New test.
	* gfortran.dg/dependency_49.f90:  New test.

From-SVN: r239977

gcc/fortran/frontend-passes.c

@@ -164,19 +164,34 @@ realloc_string_callback (gfc_code **c, int *walk_subtrees ATTRIBUTE_UNUSED,
   gfc_expr *expr1, *expr2;
   gfc_code *co = *c;
   gfc_expr *n;
+  gfc_ref *ref;
+  bool found_substr;
 
   if (co->op != EXEC_ASSIGN)
     return 0;
 
   expr1 = co->expr1;
   if (expr1->ts.type != BT_CHARACTER || expr1->rank != 0
-      || !expr1->symtree->n.sym->attr.allocatable)
+      || !gfc_expr_attr(expr1).allocatable
+      || !expr1->ts.deferred)
     return 0;
 
   expr2 = gfc_discard_nops (co->expr2);
   if (expr2->expr_type != EXPR_VARIABLE)
     return 0;
 
+  found_substr = false;
+  for (ref = expr2->ref; ref; ref = ref->next)
+    {
+      if (ref->type == REF_SUBSTRING)
+	{
+	  found_substr = true;
+	  break;
+	}
+    }
+  if (!found_substr)
+    return 0;
+
   if (!gfc_check_dependency (expr1, expr2, true))
     return 0;
 
@@ -190,7 +205,7 @@ realloc_string_callback (gfc_code **c, int *walk_subtrees ATTRIBUTE_UNUSED,
   current_code = c;
   inserted_block = NULL;
   changed_statement = NULL;
-  n = create_var (expr2, "trim");
+  n = create_var (expr2, "realloc_string");
   co->expr2 = n;
   return 0;
 }

gcc/testsuite/gfortran.dg/dependency_47.f90

+! { dg-do compile }
+! Make sure there is only one instance of a temporary variable here.
+! { dg-options "-fdump-tree-original" }
+
+SUBROUTINE prtdata(ilen)
+  INTEGER :: ilen
+  character(len=ilen), allocatable :: cline(:)
+  allocate(cline(2))
+  cline(1) = 'a'
+  cline(1)(2:3) = cline(1)(1:2)
+  cline(2) = cline(1)
+  print *,c
+END SUBROUTINE prtdata
+! { dg-final { scan-tree-dump-not "__var_" "original" } }

gcc/testsuite/gfortran.dg/dependency_49.f90

+! { dg-do compile }
+! { dg-options "-fdump-tree-original" }
+! PR fortran/71902 - make sure that component references are followed
+! for dependency analysis.
+program main
+  type foo
+     character(len=:), allocatable :: x
+  end type foo
+  type(foo) :: a
+  a%x = 'asdf'
+  a%x = a%x(2:3)
+  print *,a%x
+end program main
+! { dg-final { scan-tree-dump-times "__var_1" 4 "original" } }