From: Diego Novillo <dnovillo@redhat.com>
To: Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
Cc: Richard Henderson <rth@redhat.com>, "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: Serious problems with tree-ssa operand handling
Date: Tue, 07 Sep 2004 14:12:00 -0000 [thread overview]
Message-ID: <1094566367.21733.25.camel@localhost.localdomain> (raw)
In-Reply-To: <10409071147.AA24235@vlsi1.ultra.nyu.edu>
On Tue, 2004-09-07 at 07:47, Richard Kenner wrote:
> As I said originally, this puts a pointer into the stack of that function
> into the operands of the statement. That causes an access of junk when
> the operands are referenced.
>
No, it does not. VAR is not a GIMPLE register, follow what happens to
non-GIMPLE registers in add_stmt_operand:
1424 add_stmt_operand (tree *var_p, tree stmt, int flags)
1425 {
[ ... ]
1430
1431 var = *var_p;
1432 STRIP_NOPS (var);
[ ... ]
1445 is_real_op = is_gimple_reg (var);
1446 if (!is_real_op && !DECL_P (var))
1447 var = get_virtual_var (var);
[ ... ]
1463
1464 if (is_real_op)
1465 {
1466 /* The variable is a GIMPLE register. Add it to real operands. */
1467 if (flags & opf_is_def)
1468 append_def (var_p);
1469 else
1470 append_use (var_p);
1471 }
1472 else
1473 {
[ ... ]
1497 append_v_may_def (var);
[ ... ]
1509 append_v_must_def (var);
1510 }
[ ...]
1515 append_v_may_def (var);
[ ... ]
1520 append_vuse (var);
[ ... ]
1543 append_v_may_def (var);
1544
[ ... ]
1546 append_v_may_def (VARRAY_TREE (aliases, i));
[ ... ]
1556 append_vuse (var);
1557
[ ... ]
1559 append_vuse (VARRAY_TREE (aliases, i));
[ ... ]
1565 }
I have elided most of the logic. But you see that we only ever use
VAR_P if we are given a real operand (i.e., a symbol that
is_gimple_reg). The only reason we take the address of the variable is
because for GIMPLE regs we want to store a pointer into the operand so
that we can simplify operand replacement.
We could probably split add_stmt_operand in two so that we have a
version for GIMPLE regs and a version for others. The downside is that
some of the preparatory logic in add_stmt_operands may have to move to
the callers.
> But I shouldn't have to put in that kludge and disable both checks.
>
No. Both kludges are papering over the real problem and are wrong. I
would need a test case. Do you have a variable that is a GIMPLE reg and
at the same time belongs to an alias set or its address is taken?
Diego.
next prev parent reply other threads:[~2004-09-07 14:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-07 11:45 Richard Kenner
2004-09-07 14:12 ` Diego Novillo [this message]
2004-09-07 15:24 Richard Kenner
2004-09-07 15:27 ` Diego Novillo
2004-09-15 18:39 ` Joe Buck
2004-09-15 18:52 ` Gabriel Dos Reis
2004-09-07 20:41 Richard Kenner
2004-09-16 3:11 Richard Kenner
2004-09-16 3:23 ` Gabriel Dos Reis
2004-09-16 5:45 ` Richard Henderson
2004-09-16 11:32 Richard Kenner
2004-09-16 12:25 ` Gabriel Dos Reis
2004-09-16 15:39 ` Robert Dewar
2004-09-16 11:54 Richard Kenner
2004-09-16 14:30 ` Daniel Berlin
2004-09-16 13:31 Richard Kenner
2004-09-16 14:48 Richard Kenner
2004-09-16 15:16 ` Richard Earnshaw
2004-09-16 23:26 ` Kai Henningsen
2004-09-17 1:27 ` Erik Trulsson
2004-09-17 1:33 Richard Kenner
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