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* [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation
@ 2008-09-16 15:23 rguenth at gcc dot gnu dot org
2008-09-16 15:23 ` [Bug tree-optimization/37542] " rguenth at gcc dot gnu dot org
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-09-16 15:23 UTC (permalink / raw)
To: gcc-bugs
Related to the XFAIL of gcc.dg/tree-ssa/ssa-pre-15.c (PR37145). The general
issue is that PRE doesn't simplify expressions during phi-translation
which can be seen for example for
int foo (int i, int b)
{
int j = 1;
if (b)
j = i;
return j - i;
}
where j - i is partially redundant.
--
Summary: PRE doesn't simplify during phi-translation
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: rguenth at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
@ 2008-09-16 15:23 ` rguenth at gcc dot gnu dot org
2008-09-16 15:35 ` [Bug tree-optimization/37542] [4.4 Regression] " rguenth at gcc dot gnu dot org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-09-16 15:23 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rguenth at gcc dot gnu dot org 2008-09-16 15:22 -------
Mine. I have some patches.
--
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|UNCONFIRMED |ASSIGNED
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2008-09-16 15:22:36
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
2008-09-16 15:23 ` [Bug tree-optimization/37542] " rguenth at gcc dot gnu dot org
@ 2008-09-16 15:35 ` rguenth at gcc dot gnu dot org
2008-09-22 12:21 ` rguenth at gcc dot gnu dot org
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-09-16 15:35 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from rguenth at gcc dot gnu dot org 2008-09-16 15:34 -------
Hm, actually this is a regression :/ 4.3 produces
foo (i, b)
{
int prephitmp.7;
int pretmp.6;
int j;
int D.1550;
<bb 2>:
if (b_3(D) != 0)
goto <bb 3>;
else
goto <bb 5>;
<bb 5>:
pretmp.6_8 = 1 - i_4(D);
goto <bb 4>;
<bb 3>:
<bb 4>:
# prephitmp.7_9 = PHI <pretmp.6_8(5), 0(3)>
# j_1 = PHI <1(5), i_4(D)(3)>
D.1550_6 = prephitmp.7_9;
return D.1550_6;
}
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work| |4.3.2
Summary|PRE doesn't simplify during |[4.4 Regression] PRE doesn't
|phi-translation |simplify during phi-
| |translation
Target Milestone|--- |4.4.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
2008-09-16 15:23 ` [Bug tree-optimization/37542] " rguenth at gcc dot gnu dot org
2008-09-16 15:35 ` [Bug tree-optimization/37542] [4.4 Regression] " rguenth at gcc dot gnu dot org
@ 2008-09-22 12:21 ` rguenth at gcc dot gnu dot org
2008-10-22 3:47 ` mmitchel at gcc dot gnu dot org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-09-22 12:21 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2008-09-22 12:20 -------
Current PRE simplifies only a subset of previous PRE - see
tree-ssa-pre.c:fully_constant_expression.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
` (2 preceding siblings ...)
2008-09-22 12:21 ` rguenth at gcc dot gnu dot org
@ 2008-10-22 3:47 ` mmitchel at gcc dot gnu dot org
2008-11-01 17:12 ` rguenth at gcc dot gnu dot org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: mmitchel at gcc dot gnu dot org @ 2008-10-22 3:47 UTC (permalink / raw)
To: gcc-bugs
--
mmitchel at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
` (3 preceding siblings ...)
2008-10-22 3:47 ` mmitchel at gcc dot gnu dot org
@ 2008-11-01 17:12 ` rguenth at gcc dot gnu dot org
2008-11-01 17:13 ` rguenth at gcc dot gnu dot org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-11-01 17:12 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from rguenth at gcc dot gnu dot org 2008-11-01 17:11 -------
We need to be careful with simplifying to SSA_NAMEs as the following example
shows:
int foo (int i, int b)
{
int mask;
int result;
if (b)
mask = -1;
else
mask = 0;
result = i + 1;
result = result & mask;
return result;
}
we have a phi-translation for result & mask that is 0 or result dependent
on the path through the CFG. But we cannot insert this as a PHI as one
argument (result with value i + 1) is not available there.
The PRE of 4.3 inserts i + 1, re-generating the expression recursively and
exposing a code hoisting opportunity:
<bb 2>:
if (b_2(D) != 0)
goto <bb 5>;
else
goto <bb 3>;
<bb 5>:
pretmp.6_10 = i_5(D) + 1;
pretmp.6_11 = pretmp.6_10;
goto <bb 4>;
<bb 3>:
pretmp.6_13 = i_5(D) + 1;
<bb 4>:
# prephitmp.7_14 = PHI <pretmp.6_10(5), pretmp.6_13(3)>
# prephitmp.7_12 = PHI <pretmp.6_11(5), 0(3)>
# mask_1 = PHI <-1(5), 0(3)>
result_6 = prephitmp.7_14;
result_7 = prephitmp.7_12;
return result_7;
I don't think we want to do this now (without code hoisting implemented), but
for cases where result_6 is available we surely want it.
I'm trying to find a way to detect whether it is safe to phi-translate to
result_6.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dberlin at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
` (4 preceding siblings ...)
2008-11-01 17:12 ` rguenth at gcc dot gnu dot org
@ 2008-11-01 17:13 ` rguenth at gcc dot gnu dot org
2008-11-02 15:28 ` rguenth at gcc dot gnu dot org
2008-11-02 15:29 ` rguenth at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-11-01 17:13 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2008-11-01 17:12 -------
Created an attachment (id=16609)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16609&action=view)
preliminary patch
preliminary patch, only dealing with optimizing to constants.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
` (5 preceding siblings ...)
2008-11-01 17:13 ` rguenth at gcc dot gnu dot org
@ 2008-11-02 15:28 ` rguenth at gcc dot gnu dot org
2008-11-02 15:29 ` rguenth at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-11-02 15:28 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from rguenth at gcc dot gnu dot org 2008-11-02 15:27 -------
Subject: Bug 37542
Author: rguenth
Date: Sun Nov 2 15:26:04 2008
New Revision: 141534
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=141534
Log:
2008-11-02 Richard Guenther <rguenther@suse.de>
PR tree-optimization/37542
* tree-ssa-pre.c (fully_constant_expression): Handle more cases.
* tree-ssa-sccvn.c (vn_get_expr_for): Fix typo.
(vn_nary_op_lookup_stmt): Adjust for unary reference trees.
(vn_nary_op_insert_stmt): Likewise.
(visit_use): Likewise.
* gcc.dg/tree-ssa/ssa-pre-22.c: New testcase.
* gcc.c-torture/compile/20081101-1.c: Likewise.
Added:
trunk/gcc/testsuite/gcc.c-torture/compile/20081101-1.c
trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-22.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-ssa-pre.c
trunk/gcc/tree-ssa-sccvn.c
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug tree-optimization/37542] [4.4 Regression] PRE doesn't simplify during phi-translation
2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
` (6 preceding siblings ...)
2008-11-02 15:28 ` rguenth at gcc dot gnu dot org
@ 2008-11-02 15:29 ` rguenth at gcc dot gnu dot org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2008-11-02 15:29 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from rguenth at gcc dot gnu dot org 2008-11-02 15:27 -------
Fixed as far as constants are concerned. For the non-constant case I'll open
another bug.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37542
^ permalink raw reply [flat|nested] 9+ messages in thread
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2008-09-16 15:23 [Bug tree-optimization/37542] New: PRE doesn't simplify during phi-translation rguenth at gcc dot gnu dot org
2008-09-16 15:23 ` [Bug tree-optimization/37542] " rguenth at gcc dot gnu dot org
2008-09-16 15:35 ` [Bug tree-optimization/37542] [4.4 Regression] " rguenth at gcc dot gnu dot org
2008-09-22 12:21 ` rguenth at gcc dot gnu dot org
2008-10-22 3:47 ` mmitchel at gcc dot gnu dot org
2008-11-01 17:12 ` rguenth at gcc dot gnu dot org
2008-11-01 17:13 ` rguenth at gcc dot gnu dot org
2008-11-02 15:28 ` rguenth at gcc dot gnu dot org
2008-11-02 15:29 ` rguenth at gcc dot gnu dot org
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