re PR middle-end/41453 (use INTENT(out) for optimization)

2018-09-22  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/41453
	* trans.h (gfc_conv_expr_reference): Add optional argument
	add_clobber to prototype.
	(gfc_conv_procedure_call):  Set add_clobber argument to
	gfc_conv_procedure_reference to true for scalar, INTENT(OUT),
	non-pointer, non-allocatable, non-dummy variables whose type
	is neither BT_CHARACTER, BT_DERIVED or BT_CLASS, but only if
	the procedure is not elemental.
	* trans-expr.c (gfc_conv_procedure_reference): Add clobber
	statement before call if add_clobber is set.

2018-09-22  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/41453
	* gfortran.dg/intent_optimize_2.f90: New test.

From-SVN: r264506

5 files changed, 68 insertions, 4 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 14a1de1..6a7f7f2 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,16 @@
+2018-09-22  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/41453
+	* trans.h (gfc_conv_expr_reference): Add optional argument
+	add_clobber to prototype.
+	(gfc_conv_procedure_call):  Set add_clobber argument to
+	gfc_conv_procedure_reference to true for scalar, INTENT(OUT),
+	non-pointer, non-allocatable, non-dummy variables whose type
+	is neither BT_CHARACTER, BT_DERIVED or BT_CLASS, but only if
+	the procedure is not elemental.
+	* trans-expr.c (gfc_conv_procedure_reference): Add clobber
+	statement before call if add_clobber is set.
+
 2018-09-22  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/85603
diff --git a/gcc/fortran/trans-expr.c b/gcc/fortran/trans-expr.c
index 1453828..ae86d59 100644
--- a/gcc/fortran/trans-expr.c
+++ b/gcc/fortran/trans-expr.c
@@ -5276,8 +5276,17 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
 			}
 		    }
 		  else
-		    gfc_conv_expr_reference (&parmse, e);
-
+		    {
+		      bool add_clobber;
+		      add_clobber = fsym && fsym->attr.intent == INTENT_OUT
+			&& !fsym->attr.allocatable && !fsym->attr.pointer
+			&& !e->symtree->n.sym->attr.pointer
+			&& !e->symtree->n.sym->attr.dummy  /* See PR 41453.  */
+			&& e->ts.type != BT_CHARACTER && e->ts.type != BT_DERIVED
+			&& e->ts.type != BT_CLASS && !sym->attr.elemental;
+
+		      gfc_conv_expr_reference (&parmse, e, add_clobber);
+		    }
 		  /* Catch base objects that are not variables.  */
 		  if (e->ts.type == BT_CLASS
 			&& e->expr_type != EXPR_VARIABLE
@@ -8060,7 +8069,7 @@ gfc_conv_expr_type (gfc_se * se, gfc_expr * expr, tree type)
    values only.  */
 
 void
-gfc_conv_expr_reference (gfc_se * se, gfc_expr * expr)
+gfc_conv_expr_reference (gfc_se * se, gfc_expr * expr, bool add_clobber)
 {
   gfc_ss *ss;
   tree var;
@@ -8100,6 +8109,16 @@ gfc_conv_expr_reference (gfc_se * se, gfc_expr * expr)
 	  gfc_add_block_to_block (&se->pre, &se->post);
 	  se->expr = var;
 	}
+      else if (add_clobber)
+	{
+	  tree clobber;
+	  tree var;
+	  /* FIXME: This fails if var is passed by reference, see PR
+	     41453.  */
+	  var = expr->symtree->n.sym->backend_decl;
+	  clobber = build_clobber (TREE_TYPE (var));
+	  gfc_add_modify (&se->pre, var, clobber);
+	}
       return;
     }
 
diff --git a/gcc/fortran/trans.h b/gcc/fortran/trans.h
index 1813882..4f33a89 100644
--- a/gcc/fortran/trans.h
+++ b/gcc/fortran/trans.h
@@ -485,7 +485,8 @@ tree gfc_build_compare_string (tree, tree, tree, tree, int, enum tree_code);
 void gfc_conv_expr (gfc_se * se, gfc_expr * expr);
 void gfc_conv_expr_val (gfc_se * se, gfc_expr * expr);
 void gfc_conv_expr_lhs (gfc_se * se, gfc_expr * expr);
-void gfc_conv_expr_reference (gfc_se * se, gfc_expr *);
+void gfc_conv_expr_reference (gfc_se * se, gfc_expr * expr,
+			      bool add_clobber = false);
 void gfc_conv_expr_type (gfc_se * se, gfc_expr *, tree);
 
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7afec4f..d26e494 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-22  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/41453
+	* gfortran.dg/intent_optimize_2.f90: New test.
+
 2018-09-22  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR fortran/87318
diff --git a/gcc/testsuite/gfortran.dg/intent_optimize_2.f90 b/gcc/testsuite/gfortran.dg/intent_optimize_2.f90
new file mode 100644
index 0000000..47632bb
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/intent_optimize_2.f90
@@ -0,0 +1,26 @@
+! { dg-do compile }
+! { dg-options "-O -fno-inline -fdump-tree-optimized -fdump-tree-original" }
+! PR fortran/41453
+! Check that there is one clobber in the *.original tree, plus that
+! the constant 123456789 has been removed due to the INTENT(OUT).
+
+module x
+implicit none
+contains
+  subroutine foo(a)
+    integer, intent(out) :: a
+    a = 42
+  end subroutine foo
+end module x
+
+program main
+  use x
+  implicit none
+  integer :: a
+  a = 123456789
+  call foo(a)
+  print *,a
+end program main
+
+! { dg-final { scan-tree-dump-times "123456789" 0 "optimized" } }
+! { dg-final { scan-tree-dump-times "CLOBBER" 1 "original" } }