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* [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header
@ 2010-03-01 23:03 pinskia at gcc dot gnu dot org
2010-03-01 23:06 ` [Bug debug/43222] " pinskia at gcc dot gnu dot org
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2010-03-01 23:03 UTC (permalink / raw)
To: gcc-bugs
I Noticed this while looking into the testcase of 42897, sometimes we generate
a second DEBUG i => 0 when doing a loop copy header. The second debug
statement does not even have a line number associated with it either (but that
might be because it was from the phi).
Simple testcase:
int gif_read_lzw(int input_code_size)
{
int i, incode;
static short fresh = 0, code_size, set_code_size, clear_code, table[4096],
*sp;
set_code_size = input_code_size;
clear_code = 1 << input_code_size;
for (i = 0; i < clear_code; i ++)
table[i] = i;
}
--
Summary: two DEBUG i => 0 generated after loop copy header
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pinskia at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
@ 2010-03-01 23:06 ` pinskia at gcc dot gnu dot org
2010-03-01 23:14 ` pinskia at gcc dot gnu dot org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2010-03-01 23:06 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2010-03-01 23:05 -------
And there are actually two duplicated debug statements. One for the i => 0 and
then one for i => i_11
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
2010-03-01 23:06 ` [Bug debug/43222] " pinskia at gcc dot gnu dot org
@ 2010-03-01 23:14 ` pinskia at gcc dot gnu dot org
2010-03-01 23:20 ` pinskia at gcc dot gnu dot org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2010-03-01 23:14 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2010-03-01 23:14 -------
Here is a simplier testcase which shows the problem is even worse:
int gif_read_lzw(int input_code_size)
{
int i;
short code_size = 0;
for (i = 0; i < input_code_size; i ++)
code_size ++;
return code_size;
}
--- CUT ---
We have now 8 debug statements after loop copy header when we really only need
4 (2 before the loop and 2 inside the loop). Why are we duplicating already
emitted debug statements?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
2010-03-01 23:06 ` [Bug debug/43222] " pinskia at gcc dot gnu dot org
2010-03-01 23:14 ` pinskia at gcc dot gnu dot org
@ 2010-03-01 23:20 ` pinskia at gcc dot gnu dot org
2010-03-02 7:55 ` jakub at gcc dot gnu dot org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2010-03-01 23:20 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from pinskia at gcc dot gnu dot org 2010-03-01 23:20 -------
And nothing removes the duplicated debug statements that are outside the loop
until rtl dce comes around. And it removes the debug statements which had line
information too.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
` (2 preceding siblings ...)
2010-03-01 23:20 ` pinskia at gcc dot gnu dot org
@ 2010-03-02 7:55 ` jakub at gcc dot gnu dot org
2010-03-02 11:13 ` jakub at gcc dot gnu dot org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakub at gcc dot gnu dot org @ 2010-03-02 7:55 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from jakub at gcc dot gnu dot org 2010-03-02 07:54 -------
Line info on debug stmts/DEBUG_INSNs is ignored.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
` (3 preceding siblings ...)
2010-03-02 7:55 ` jakub at gcc dot gnu dot org
@ 2010-03-02 11:13 ` jakub at gcc dot gnu dot org
2010-06-02 6:28 ` aoliva at gcc dot gnu dot org
2010-06-11 11:45 ` aoliva at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: jakub at gcc dot gnu dot org @ 2010-03-02 11:13 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from jakub at gcc dot gnu dot org 2010-03-02 11:12 -------
The extra DEBUG stmts or DEBUG_INSNs only consume memory, they shouldn't affect
debug info generation, though perhaps it wouldn't hurt once or twice during
gimple optimizations and once or twice during RTL optimizations to get rid of
redundant DEBUG stmts resp. DEBUG_INSNs (where redundant is one where for the
same variable there is another DEBUG stmt or DEBUG_INSN after it not separated
by any real statements or insns/labels.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
` (4 preceding siblings ...)
2010-03-02 11:13 ` jakub at gcc dot gnu dot org
@ 2010-06-02 6:28 ` aoliva at gcc dot gnu dot org
2010-06-11 11:45 ` aoliva at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: aoliva at gcc dot gnu dot org @ 2010-06-02 6:28 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from aoliva at gcc dot gnu dot org 2010-06-02 06:28 -------
Andrew, the debug stmts are indeed originally from the loop header's PHI nodes.
Before ch we have:
i_1 = <init>;
# i => i_1
goto <header>;
<body>:
i_3 = <whatever>(i_2);
# i => i_3
<header>:
i_2 = PHI <i_1, i_3>;
# i => i_2
if (<cond>) goto <body>; else goto <exit>;
copy_loop_header turns this into:
i_1 = <init>;
# i => i_1
<copy>:
i_4 = PHI <i_1>;
# i => i_4
if (<cond>) goto <body>; else goto <exit>;
<body>:
i_3 = <whatever>(i_2);
# i => i_3
<header>:
i_2 = PHI <i_3>;
# i => i_2
if (<cond>) goto <body>; else goto <exit>;
and that's correct. Then cfgcleanup realizes the headers can be merged with
their preds, and that kills the PHI nodes, but there's no reason why this
should kill the debug stmts.
Of course we could arrange for some cleanup passes to detect and remove debug
stmts in case they become redundant, but I don't see that we have a bug here.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug debug/43222] two DEBUG i => 0 generated after loop copy header
2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
` (5 preceding siblings ...)
2010-06-02 6:28 ` aoliva at gcc dot gnu dot org
@ 2010-06-11 11:45 ` aoliva at gcc dot gnu dot org
6 siblings, 0 replies; 8+ messages in thread
From: aoliva at gcc dot gnu dot org @ 2010-06-11 11:45 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from aoliva at gcc dot gnu dot org 2010-06-11 11:45 -------
Not a bug
--
aoliva at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43222
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2010-06-11 11:45 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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2010-03-01 23:03 [Bug debug/43222] New: two DEBUG i => 0 generated after loop copy header pinskia at gcc dot gnu dot org
2010-03-01 23:06 ` [Bug debug/43222] " pinskia at gcc dot gnu dot org
2010-03-01 23:14 ` pinskia at gcc dot gnu dot org
2010-03-01 23:20 ` pinskia at gcc dot gnu dot org
2010-03-02 7:55 ` jakub at gcc dot gnu dot org
2010-03-02 11:13 ` jakub at gcc dot gnu dot org
2010-06-02 6:28 ` aoliva at gcc dot gnu dot org
2010-06-11 11:45 ` aoliva at gcc dot gnu dot org
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