This fixes an old issue in the compiler, whereby it unexpectedly generates a
read of a volatile variable with scalar type passed as Out parameter to a
subprogram; the subtlety being that the side-effects of the parameter viewed
as a name still need to be evaluated prior to the call.
Tested on x86_64-suse-linux, applied on the mainline.
2013-11-18 Eric Botcazou <ebotca...@adacore.com>
* gcc-interface/trans.c (Call_to_gnu): For an Out parameter passed by
copy and that don't need to be copied in, only evaluate its address.
2013-11-18 Eric Botcazou <ebotca...@adacore.com>
* gnat.dg/volatile11.adb: New test.
* gnat.dg/volatile11_pkg.ad[sb]: New helper.
--
Eric BotcazouIndex: gcc-interface/trans.c
===================================================================
--- gcc-interface/trans.c (revision 204913)
+++ gcc-interface/trans.c (working copy)
@@ -4130,9 +4130,7 @@ Call_to_gnu (Node_Id gnat_node, tree *gn
gnu_name
= convert (TREE_TYPE (TYPE_FIELDS (TREE_TYPE (gnu_name))), gnu_name);
- /* If we have not saved a GCC object for the formal, it means it is an
- Out parameter not passed by reference and that need not be copied in.
- Otherwise, first see if the parameter is passed by reference. */
+ /* First see if the parameter is passed by reference. */
if (is_true_formal_parm && DECL_BY_REF_P (gnu_formal))
{
if (Ekind (gnat_formal) != E_In_Parameter)
@@ -4178,6 +4176,9 @@ Call_to_gnu (Node_Id gnat_node, tree *gn
gnu_formal_type = TREE_TYPE (gnu_formal);
gnu_actual = build_unary_op (ADDR_EXPR, gnu_formal_type, gnu_actual);
}
+
+ /* Then see if the parameter is an array passed to a foreign convention
+ subprogram. */
else if (is_true_formal_parm && DECL_BY_COMPONENT_PTR_P (gnu_formal))
{
gnu_formal_type = TREE_TYPE (gnu_formal);
@@ -4198,6 +4199,8 @@ Call_to_gnu (Node_Id gnat_node, tree *gn
but this is the most likely to work in all cases. */
gnu_actual = build_unary_op (ADDR_EXPR, gnu_formal_type, gnu_actual);
}
+
+ /* Then see if the parameter is passed by descriptor. */
else if (is_true_formal_parm && DECL_BY_DESCRIPTOR_P (gnu_formal))
{
gnu_actual = convert (gnu_formal_type, gnu_actual);
@@ -4214,6 +4217,8 @@ Call_to_gnu (Node_Id gnat_node, tree *gn
(TREE_TYPE (TREE_TYPE (gnu_formal)),
gnu_actual, gnat_actual));
}
+
+ /* Otherwise the parameter is passed by copy. */
else
{
tree gnu_size;
@@ -4221,11 +4226,18 @@ Call_to_gnu (Node_Id gnat_node, tree *gn
if (Ekind (gnat_formal) != E_In_Parameter)
gnu_name_list = tree_cons (NULL_TREE, gnu_name, gnu_name_list);
+ /* If we didn't create a PARM_DECL for the formal, this means that
+ it is an Out parameter not passed by reference and that need not
+ be copied in. In this case, the value of the actual need not be
+ read. However, we still need to make sure that its side-effects
+ are evaluated before the call, so we evaluate its address. */
if (!is_true_formal_parm)
{
- /* Make sure side-effects are evaluated before the call. */
if (TREE_SIDE_EFFECTS (gnu_name))
- append_to_statement_list (gnu_name, &gnu_stmt_list);
+ {
+ tree addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_name);
+ append_to_statement_list (addr, &gnu_stmt_list);
+ }
continue;
}
-- { dg-do run }
-- { dg-options "-O -gnatp" }
with Volatile11_Pkg; use Volatile11_Pkg;
procedure Volatile11 is
Value : Integer := 1;
Bit1 : Boolean := false;
pragma Volatile (Bit1);
Bit2 : Boolean := false;
pragma Volatile (Bit2);
Bit3 : Boolean := false;
pragma Volatile (Bit3);
Bit4 : Boolean := false;
pragma Volatile (Bit4);
Bit5 : Boolean := false;
pragma Volatile (Bit5);
Bit6 : Boolean := false;
pragma Volatile (Bit6);
Bit7 : Boolean := false;
pragma Volatile (Bit7);
Bit8 : Boolean := false;
pragma Volatile (Bit8);
begin
Bit_Test(Input => Value,
Output1 => Bit1,
Output2 => Bit2,
Output3 => Bit3,
Output4 => Bit4,
Output5 => Bit5,
Output6 => Bit6,
Output7 => Bit7,
Output8 => F.all);
-- Check that F is invoked before Bit_Test
if B /= True then
raise Program_Error;
end if;
end;
package body Volatile11_Pkg is
procedure Bit_Test(Input : in Integer;
Output1 : out Boolean; Output2 : out Boolean;
Output3 : out Boolean; Output4 : out Boolean;
Output5 : out Boolean; Output6 : out Boolean;
Output7 : out Boolean; Output8 : out Boolean) is
begin
Output8 := B;
Output7 := Input = 7;
Output6 := Input = 6;
Output5 := Input = 5;
Output4 := Input = 4;
Output3 := Input = 3;
Output2 := Input = 2;
Output1 := Input = 1;
end Bit_Test;
function F return Ptr is
begin
B := True;
return B'Access;
end;
end Volatile11_Pkg;
package Volatile11_Pkg is
procedure Bit_Test(Input : in Integer;
Output1 : out Boolean; Output2 : out Boolean;
Output3 : out Boolean; Output4 : out Boolean;
Output5 : out Boolean; Output6 : out Boolean;
Output7 : out Boolean; Output8 : out Boolean);
type Ptr is access all Boolean;
B : aliased Boolean := False;
function F return Ptr;
end Volatile11_Pkg;
