[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #11 from rguenth at gcc dot gnu dot org 2007-09-06 12:13
---
The extra store you still see is caused by -ftracer duplicating it.
Optimizations
after that don't catch that (because of the intervening possibly aliasing loads
I guess):
(insn 25 24 27 4 t.ii:3 (set (mem/s:SI (reg/f:DI 102) [4 .D.2014.a+0
S4 A64])
(reg:SI 75)) 47 {*movsi_1} (expr_list:REG_DEAD (reg:SI 75)
(expr_list:REG_EQUAL (plus:SI (mem/s:SI (reg/f:DI 102) [4
.D.2014.a+0 S4 A64])
(const_int 4 [0x4]))
(nil
(insn 27 25 28 4 t.ii:18 (set (reg:DI 78 [ .addr ])
(zero_extend:DI (mem/s:SI (reg/f:DI 101) [4 .addr+0 S4
A64]))) 120 {zero_extendsidi2_rex64} (nil))
...
(insn 96 95 97 4 t.ii:3 (parallel [
(set (reg:SI 83)
(plus:SI (reg:SI 76 [ .D.2014.a ])
(const_int 6 [0x6])))
(clobber (reg:CC 17 flags))
]) 235 {*addsi_1} (expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_DEAD (reg:SI 84 [ .D.2014.a ])
(nil
(insn 97 96 98 4 t.ii:3 (set (mem/s:SI (reg/f:DI 102) [4 .D.2014.a+0
S4 A64])
(reg:SI 83)) 47 {*movsi_1} (expr_list:REG_EQUAL (plus:SI (mem/s:SI
(reg/f:DI 102) [4 .D.2014.a+0 S4 A64])
(const_int 2 [0x2]))
(expr_list:REG_DEAD (reg:SI 83)
(nil
If you build without -ftracer or without -fforce-addr it works (but won't
combine the add on one path). But.. -ftracer was supposed to be moved
to the tree level...
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #10 from wouter dot vermaelen at scarlet dot be 2007-09-06 11:48 --- I'm sorry, but can you recheck? The testcase at the top of this bug report still generates the same asm code for me. -- wouter dot vermaelen at scarlet dot be changed: What|Removed |Added Severity|enhancement |normal http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #9 from rguenth at gcc dot gnu dot org 2007-09-06 09:06 --- Subject: Bug 33302 Author: rguenth Date: Thu Sep 6 09:05:58 2007 New Revision: 128180 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128180 Log: 2007-09-06 Richard Guenther <[EMAIL PROTECTED]> PR tree-optimization/33302 * tree-ssa-dse.c (tree_ssa_dse): Connect infinite loops to the exit block before doing the post-dominator walk. * domwalk.c (walk_dominator_tree): The exit block is interesting even if it is not reachable. * gcc.dg/tree-ssa/ssa-dse-11.c: New testcase. Added: trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-11.c Modified: trunk/gcc/ChangeLog trunk/gcc/domwalk.c trunk/gcc/testsuite/ChangeLog -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #8 from rguenth at gcc dot gnu dot org 2007-09-06 09:06 --- Fixed. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution||FIXED Target Milestone|--- |4.3.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #7 from rakdver at kam dot mff dot cuni dot cz 2007-09-05
14:30 ---
Subject: Re: dead-store not eliminated
> > > Ah, I only found add_noreturn_fake_exit_edges which obviously didn't help.
> > > connect_infinite_loops_to_exit does. Thx.
> >
> > dominance.c contains code (probably buggy) that adds such edges implicitly,
> > so
> > this should not be needed.
>
> Maybe, but then domwalk.c is buggy as walk_dominator_tree does
>
> while (true)
> {
> /* Don't worry about unreachable blocks. */
> if (EDGE_COUNT (bb->preds) > 0 || bb == ENTRY_BLOCK_PTR)
> {
>
> and obviously in my case bb (the exit block) has no preds. Maybe
> simply special-casing EXIT_BLOCK_PTR as well helps.
Yes, that seems reasonable (I think domwalk was originally only used
for dominator tree walks, so it may contain this kind of bugs for
post-dominator walks)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #6 from rguenther at suse dot de 2007-09-05 14:17 ---
Subject: Re: dead-store not eliminated
On Wed, 5 Sep 2007, rakdver at gcc dot gnu dot org wrote:
> (In reply to comment #4)
> > Ah, I only found add_noreturn_fake_exit_edges which obviously didn't help.
> > connect_infinite_loops_to_exit does. Thx.
>
> dominance.c contains code (probably buggy) that adds such edges implicitly, so
> this should not be needed.
Maybe, but then domwalk.c is buggy as walk_dominator_tree does
while (true)
{
/* Don't worry about unreachable blocks. */
if (EDGE_COUNT (bb->preds) > 0 || bb == ENTRY_BLOCK_PTR)
{
and obviously in my case bb (the exit block) has no preds. Maybe
simply special-casing EXIT_BLOCK_PTR as well helps.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #5 from rakdver at gcc dot gnu dot org 2007-09-05 12:51 --- (In reply to comment #4) > Ah, I only found add_noreturn_fake_exit_edges which obviously didn't help. > connect_infinite_loops_to_exit does. Thx. dominance.c contains code (probably buggy) that adds such edges implicitly, so this should not be needed. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #4 from rguenth at gcc dot gnu dot org 2007-09-05 12:41 --- Ah, I only found add_noreturn_fake_exit_edges which obviously didn't help. connect_infinite_loops_to_exit does. Thx. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot |dot org |org Status|NEW |ASSIGNED Last reconfirmed|2007-09-05 11:33:31 |2007-09-05 12:41:53 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #3 from steven at gcc dot gnu dot org 2007-09-05 12:35 --- You can connect the exits by inserting fake edges. See add_noreturn_fake_exit_edges and connect_infinite_loops_to_exit. Not sure which one you would need in this case. Just be sure to call it before computing (post)dominator info. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #2 from rguenth at gcc dot gnu dot org 2007-09-05 11:48 ---
DSE does a post-dominator walk starting from the exit block. But the exit
block
has no predecessors because the function does never exit ;)
void foo(int *p)
{
while (1)
{
*p = 0;
*p = 0;
}
}
after DSE:
foo (p)
{
:
:
*p_1(D) = 0;
*p_1(D) = 0;
goto ;
}
I suppose more post-dom walk optimizations are affected by this "bug".
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
[Bug tree-optimization/33302] dead-store not eliminated
--- Comment #1 from rguenth at gcc dot gnu dot org 2007-09-05 11:33 --- While RTL dse eliminates the redundant store to this->D.2013.a, tree-level DSE does not do so. (RTL dse also fails with -O3 -fforce-addr -ftracer) : # VUSE D.2089_34 = this_2(D)->D.2013.a; D.2090_35 = (unsigned int) D.2089_34; D.2091_36 = D.2090_35 + 2; D.2092_37 = (int) D.2091_36; # tab_62 = VDEF # SMT.9_63 = VDEF this_2(D)->D.2013.a = D.2092_37; D.2095_40 = D.2091_36 + 2; D.2096_41 = (int) D.2095_40; # tab_64 = VDEF # SMT.9_65 = VDEF this_2(D)->D.2013.a = D.2096_41; # VUSE D.2087_42 = this_2(D)->addr; D.2097_43 = (long unsigned int) D.2087_42; D.2098_44 = D.2097_43 & 255; D.2099_45 = p_33 + D.2098_44; # VUSE b_46 = *D.2099_45; goto ; clearly there is no reason for DSE not to discard the store. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added CC||rguenth at gcc dot gnu dot ||org Severity|normal |enhancement Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Keywords||missed-optimization, TREE Last reconfirmed|-00-00 00:00:00 |2007-09-05 11:33:31 date|| Summary|follow-up on bug 33291 |dead-store not eliminated |dead-store not eliminated | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33302
