[Bug fortran/45742] VOLATILE has no effect

[Bug fortran/45742] VOLATILE has no effect

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2010.11.12 20:03:13
                 CC|                            |burnus at gcc dot gnu.org
            Summary|VOLATI                      |VOLATILE has no effect
     Ever Confirmed|0                           |1

--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2010-11-12 20:03:13 UTC ---
Apparently, VOLATILE has no effect at all.  Another test case:

ig25@linux-fd1f:~/Krempel/Volatile> cat op2.f90
subroutine foo(j)  
  integer, volatile :: j                                              
 integer :: b
 b = j + j + j + j                        
  print *,b                                               
end                                                                             
ig25@linux-fd1f:~/Krempel/Volatile> gfortran -S -O3 -fdump-tree-optimized
op2.f90                    
ig25@linux-fd1f:~/Krempel/Volatile> cat op2.f90.144t.optimized

;; Function foo (foo_)

foo (integer(kind=4) & restrict j)
{
  struct __st_parameter_dt dt_parm.0;
  integer(kind=4) b;
  integer(kind=4) b.1;
  integer(kind=4) D.1504;
  integer(kind=4) D.1503;
  integer(kind=4) D.1502;

<bb 2>:
  D.1502_3 = *j_1(D);
  D.1503_4 = D.1502_3 + D.1502_3;
  D.1504_6 = D.1502_3 + D.1503_4;
  b.1_8 = D.1502_3 + D.1504_6;
  b = b.1_8;
  dt_parm.0.common.filename = &"op2.f90"[1]{lb: 1 sz: 1};
  dt_parm.0.common.line = 5;
  dt_parm.0.common.flags = 128;
  dt_parm.0.common.unit = 6;
  _gfortran_st_write (&dt_parm.0);
  _gfortran_transfer_integer_write (&dt_parm.0, &b, 4);
  _gfortran_st_write_done (&dt_parm.0);
  return;

}

Tobias, any ideas?  You implemented this a few years ago, if I remember
correctly :-)

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-12 20:22:24 UTC ---
(In reply to comment #1)
> Apparently, VOLATILE has no effect at all.  Another test case:
[...]
> Tobias, any ideas?

No idea:

$ LANG= gfortran -v 2>&1|grep -E 'experi|Targ'
Target: x86_64-unknown-linux-gnu
gcc version 4.6.0 20101111 (experimental) [trunk revision 166614] (GCC) 

$ gfortran -fdump-tree-original -fdump-tree-optimized -O3 -c test.f90

$ cat test.f90.003t.original
...
  integer(kind=4) b;
  volatile integer(kind=4) j;

  b = ((j + j) + j) + j;
...

$ cat test.f90.144t.optimized
...
  j.1_1 ={v} j;
  j.1_2 ={v} j;
  D.1508_3 = j.1_2 + j.1_2;
  j.1_4 ={v} j;
  D.1509_5 = D.1508_3 + j.1_4;
  j.1_6 ={v} j;
  b.2_7 = D.1509_5 + j.1_6;

Looks good!

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #3 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-12 20:33:36 UTC ---
I think the first test case is wrongly folded already by the front end:

program main
  integer, volatile :: j
  if (j>j) call notfound
end program main

Gives the original dump:

MAIN__ ()
{
  volatile integer(kind=4) j;

  L.1:;
}

 * * *

For some reason, also:

program main
  integer, volatile :: j, k
  if (j>k) call notfound
end program main

does not give a link error. The optimized dump has:
  j.1_8 ={v} j;
  k.2_9 ={v} k;
  if (j.1_8 > k.2_9)
    goto <bb 3>;
<bb 3>:
  notfound ();

which looks OK, but there is no link error?!?

[Bug fortran/45742] VOLATILE has no effect

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #4 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2010-11-12 21:56:08 UTC ---
(In reply to comment #2)
> (In reply to comment #1)
> > Apparently, VOLATILE has no effect at all.  Another test case:
> [...]
> > Tobias, any ideas?
> 
> No idea:
>
> $ cat test.f90.003t.original
> ...
>   integer(kind=4) b;
>   volatile integer(kind=4) j;
> 
>   b = ((j + j) + j) + j;

I see:

foo (integer(kind=4) & restrict j)
{
  integer(kind=4) b;

  b = ((*j + *j) + *j) + *j;
  {
    struct __st_parameter_dt dt_parm.0;

so the volatile is missing.  Huh?

This may be a Heisenbug.  Unfortunately, valgrind doesn't work on
my system.

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-12 23:02:06 UTC ---
(In reply to comment #4)
> >   volatile integer(kind=4) j;

> I see:
> foo (integer(kind=4) & restrict j)
> so the volatile is missing.  Huh?

Seemingly, we have tested different things - I looked a local variable "j"
which works while you looked at a dummy variable, which does not seem to work.
Thus, not a Heisenbug.


If one prints the symbol "j" one gets as backend declaration:

(gdb) p debug_tree (...->symtree->n.sym->backend_decl)
 <parm_decl 0x2aaaace2e880 j
    type <reference_type 0x2aaaacf1d930
        type <integer_type 0x2aaaace37498 integer(kind=4) public SI
            size <integer_cst 0x2aaaace276e0 constant 32>
            unit size <integer_cst 0x2aaaace273e8 constant 4>
            align 32 symtab 0 alias set -1 canonical type 0x2aaaace37498
precision 32 min <integer_cst 0x2aaaace27668 -2147483648> max <integer_cst
0x2aaaace27690 2147483647>
            pointer_to_this <pointer_type 0x2aaaace443f0> reference_to_this
<reference_type 0x2aaaacf1d888>>
        unsigned restrict DI
        size <integer_cst 0x2aaaace277a8 constant 64>
        unit size <integer_cst 0x2aaaace277d0 constant 8>
        align 64 symtab 0 alias set -1 canonical type 0x2aaaacf1d930>
    readonly used unsigned DI passed-by-reference file jfff4322.f90 line 1 col
0 size <integer_cst 0x2aaaace277a8 64> unit size <integer_cst 0x2aaaace277d0 8>
    align 64 context <function_decl 0x2aaaacf1e600 foo> arg-type
<reference_type 0x2aaaacf1d930>>


While for my local variable, one gets:

 <var_decl 0x2aaaacf200a0 j
    type <integer_type 0x2aaaacf1d9d8 integer(kind=4) volatile SI
        size <integer_cst 0x2aaaace276e0 constant 32>
        unit size <integer_cst 0x2aaaace273e8 constant 4>
        align 32 symtab 0 alias set -1 canonical type 0x2aaaacf1d9d8 precision
32 min <integer_cst 0x2aaaace27668 -2147483648> max <integer_cst 0x2aaaace27690
2147483647>>
    volatile used SI file jfff4322.f90 line 2 col 0 size <integer_cst
0x2aaaace276e0 32> unit size <integer_cst 0x2aaaace273e8 4>
    align 32 context <function_decl 0x2aaaacf1e600 foo> chain <var_decl
0x2aaaacf20000 b>>


Thus, the latter properly has the proper values. Seemingly, a THREE_IS_VOLATILE
or TYPE_QUAL_VOLATILE is missing somewhere.

 * * *

For the test case in comment 0 alias comment 3 part one, the reason is clear:
The fold-const.c's fold_build2_stat_loc with code=GT_EXPR always and
unconditionally folds "j > j" to "false".

I have no idea whether that's OK or not - but as a C test case behaves
differently, that's now tracked as PR 46458.

 * * *

Second test case of comment 3: Why is the "volatile" lost between the SSA tree
(-fdump-tree-optimize still has it) and RTL (-fdump-rtl-all, which does not
have any "mem/v" reference)? I am currently looking into that issue.

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

Bug 45742 depends on bug 46458, which changed state.

Bug 46458 Summary: Volatile status ignored for  "(j > j)" during fold_comparison of fold-const.c
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46458

           What    |Old Value                   |New Value
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #6 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-12 23:30:00 UTC ---
*** Bug 46458 has been marked as a duplicate of this bug. ***

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #7 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-12 23:32:06 UTC ---
OK. The (j>j) and the tree->RTL issue are solved by the following patch. Thanks
to Andrew, Ian, Richard et al. (at #gcc) for the debugging help.


diff --git a/gcc/fortran/trans-common.c b/gcc/fortran/trans-common.c
index 486fbbb..1f59a69 100644
--- a/gcc/fortran/trans-common.c
+++ b/gcc/fortran/trans-common.c
@@ -322,6 +322,7 @@ build_field (segment_info *h, tree union_type,
record_layout_info rli)
     {
       tree new_type;
       TREE_THIS_VOLATILE (field) = 1;
+      TREE_SIDE_EFFECTS (field) = 1;
       new_type = build_qualified_type (TREE_TYPE (field), TYPE_QUAL_VOLATILE);
       TREE_TYPE (field) = new_type;
     }
diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
index 3f068de..845c96b 100644
--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -555,6 +555,7 @@ gfc_finish_var_decl (tree decl, gfc_symbol * sym)
   if (sym->attr.volatile_)
     {
       TREE_THIS_VOLATILE (decl) = 1;
+      TREE_SIDE_EFFECTS (decl) = 1;
       new_type = build_qualified_type (TREE_TYPE (decl), TYPE_QUAL_VOLATILE);
       TREE_TYPE (decl) = new_type;
     }

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #8 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-12 23:55:06 UTC ---
The issue with the dummy is: Volatile will be set in gfc_get_symbol_decl - but
only if there is no backend declaration. For DUMMY arguments there is.

Thus, one needs to handle them differently.

Patch:

--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -1944,10 +1945,19 @@ create_function_arglist (gfc_symbol * sym)
       if (f->sym->attr.proc_pointer)
         type = build_pointer_type (type);

+      if (f->sym->attr.volatile_)
+       type = build_qualified_type (type, TYPE_QUAL_VOLATILE);
+
       /* Build the argument declaration.  */
       parm = build_decl (input_location,
                         PARM_DECL, gfc_sym_identifier (f->sym), type);

+      if (f->sym->attr.volatile_)
+       {
+         TREE_THIS_VOLATILE (parm) = 1;
+         TREE_SIDE_EFFECTS (parm) = 1;
+       }
+
       /* Fill in arg stuff.  */
       DECL_CONTEXT (parm) = fndecl;
       DECL_ARG_TYPE (parm) = TREE_VALUE (typelist);

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #9 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-13 00:25:13 UTC ---
Test case:

--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/volatile12.f90
@@ -0,0 +1,16 @@
+! { dg-do compile }
+! { dg-options "-fdump-tree-optimized -O3" }
+!
+! PR fortran/45742
+!
+
+subroutine sub(arg)
+  integer, volatile :: arg
+  if (arg /= arg) call I_dont_exist()
+end
+
+! { dg-final { scan-tree-dump "integer.kind=.. . volatile arg" "optimized" } }
+! { dg-final { scan-tree-dump-times " =.v. arg;" 2 "optimized" } }
+! { dg-final { scan-tree-dump "i_dont_exist" "optimized" } }
+! { dg-final { cleanup-tree-dump "original" } }

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #10 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-13 10:29:08 UTC ---
Author: burnus
Date: Sat Nov 13 10:29:04 2010
New Revision: 166701

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166701
Log:
2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * trans-common.c (build_field): Add TREE_SIDE_EFFECTS for
        * volatile.
        * trans-decl.c (gfc_finish_var_decl): Ditto.
        (create_function_arglist): Handle volatile dummy arguments.

2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * gfortran.dg/volatile12.f90: New.


Added:
    trunk/gcc/testsuite/gfortran.dg/volatile12.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/trans-common.c
    trunk/gcc/fortran/trans-decl.c
    trunk/gcc/testsuite/ChangeLog

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #11 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-13 11:46:32 UTC ---
Author: burnus
Date: Sat Nov 13 11:46:25 2010
New Revision: 166702

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166702
Log:
2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * gfortran.dg/volatile12.f90: Use the right three in
        * cleanup-tree-dump.


Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/volatile12.f90

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #13 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-13 17:25:31 UTC ---
Author: burnus
Date: Sat Nov 13 17:25:28 2010
New Revision: 166715

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166715
Log:
2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * trans-common.c (build_field): Add TREE_SIDE_EFFECTS for
        * volatile.
        * trans-decl.c (gfc_finish_var_decl): Ditto.
        (create_function_arglist): Handle volatile dummy arguments.

2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * gfortran.dg/volatile12.f90: New.


Added:
    branches/gcc-4_4-branch/gcc/testsuite/gfortran.dg/volatile12.f90
Modified:
    branches/gcc-4_4-branch/gcc/fortran/ChangeLog
    branches/gcc-4_4-branch/gcc/fortran/trans-common.c
    branches/gcc-4_4-branch/gcc/fortran/trans-decl.c
    branches/gcc-4_4-branch/gcc/testsuite/ChangeLog

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

--- Comment #12 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-13 17:23:54 UTC ---
Author: burnus
Date: Sat Nov 13 17:23:49 2010
New Revision: 166714

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=166714
Log:
2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * trans-common.c (build_field): Add TREE_SIDE_EFFECTS for
        * volatile.
        * trans-decl.c (gfc_finish_var_decl): Ditto.
        (create_function_arglist): Handle volatile dummy arguments.

2010-11-13  Tobias Burnus  <burnus@net-b.de>

        PR fortran/45742
        * gfortran.dg/volatile12.f90: New.


Added:
    branches/gcc-4_5-branch/gcc/testsuite/gfortran.dg/volatile12.f90
Modified:
    branches/gcc-4_5-branch/gcc/fortran/ChangeLog
    branches/gcc-4_5-branch/gcc/fortran/trans-common.c
    branches/gcc-4_5-branch/gcc/fortran/trans-decl.c
    branches/gcc-4_5-branch/gcc/testsuite/ChangeLog

[Bug fortran/45742] VOLATILE has no effect

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45742

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #14 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-11-13 17:27:06 UTC ---
FIXED on the trunk (4.6) and the 4.5 and 4.4 branches.

Thanks for the report.