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* [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization
@ 2004-11-20 16:30 falk at debian dot org
2004-11-20 16:32 ` [Bug rtl-optimization/18577] " pinskia at gcc dot gnu dot org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: falk at debian dot org @ 2004-11-20 16:30 UTC (permalink / raw)
To: gcc-bugs
Test case:
static float tfcos12[3];
__attribute__((noinline)) double f(double x) { return x; }
int g;
int main(void) {
int i, j;
for (i = 0; i < 1; i++)
tfcos12[i] = 0.5;
for (i = 0; i < 1; i++) {
tfcos12[i] = 0.5 * f(i);
for (j = 0; j < 12; j++)
g++;
}
return 0;
}
% gcc -funroll-all-loops -O2 test.c && ./a.out
zsh: floating point exception (core dumped) ./a.out
The reason is that the constant 0.5 is first used and then loaded:
[...]
cpys $f10,$f10,$f2 # use $f10
lds $f10,$LC0($1) !gprellow # before loading it
[...]
mult $f2,$f0,$f0 # and this FPEs
This does not happen without -funroll-all-loops. Also not at -O, or with
3.4.
--
Summary: [3.3 regression] variable use moved before
initialization
Product: gcc
Version: 3.3.5
Status: UNCONFIRMED
Keywords: wrong-code
Severity: critical
Priority: P2
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: falk at debian dot org
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: alphaev68-unknown-linux-gnu
GCC host triplet: alphaev68-unknown-linux-gnu
GCC target triplet: alphaev68-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug rtl-optimization/18577] [3.3 regression] variable use moved before initialization
2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
@ 2004-11-20 16:32 ` pinskia at gcc dot gnu dot org
2004-11-21 2:33 ` falk at debian dot org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-11-20 16:32 UTC (permalink / raw)
To: gcc-bugs
--
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |3.3.6
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug rtl-optimization/18577] [3.3 regression] variable use moved before initialization
2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
2004-11-20 16:32 ` [Bug rtl-optimization/18577] " pinskia at gcc dot gnu dot org
@ 2004-11-21 2:33 ` falk at debian dot org
2004-11-21 7:14 ` ebotcazou at gcc dot gnu dot org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: falk at debian dot org @ 2004-11-21 2:33 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From falk at debian dot org 2004-11-21 02:33 -------
The bug seems to be caused by the loop unroller making a pseudo local
to be able to duplicate it while it is still needed outside of the loop.
Reverting Eric Botcazou's patch for rtl-optimization/11841, which is
also about this, fixes the problem. I don't really understand what's going
on, but is it possible we still have to look at the pseudo luids and not
only the note luids? Like this?
diff -u -p -r1.184.2.9 unroll.c
--- unroll.c 17 May 2004 21:05:48 -0000 1.184.2.9
+++ unroll.c 21 Nov 2004 02:30:41 -0000
@@ -794,6 +794,8 @@ unroll_loop (loop, insn_count, strength_
for (r = FIRST_PSEUDO_REGISTER; r < max_reg_before_loop; ++r)
if (REGNO_FIRST_UID (r) > 0 && REGNO_FIRST_UID (r) < max_uid_for_loop
&& REGNO_FIRST_LUID (r) >= copy_start_luid
+ && REGNO_LAST_UID (r) > 0 && REGNO_LAST_UID (r) < max_uid_for_loop
+ && REGNO_LAST_LUID (r) <= copy_end_luid
&& REGNO_LAST_NOTE_UID (r) > 0 && REGNO_LAST_NOTE_UID (r) <
max_uid_for_loop
&& REGNO_LAST_NOTE_LUID (r) <= copy_end_luid)
{
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |ebotcazou at gcc dot gnu dot
| |org
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug rtl-optimization/18577] [3.3 regression] variable use moved before initialization
2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
2004-11-20 16:32 ` [Bug rtl-optimization/18577] " pinskia at gcc dot gnu dot org
2004-11-21 2:33 ` falk at debian dot org
@ 2004-11-21 7:14 ` ebotcazou at gcc dot gnu dot org
2004-11-21 9:07 ` ebotcazou at gcc dot gnu dot org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2004-11-21 7:14 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ebotcazou at gcc dot gnu dot org 2004-11-21 07:14 -------
> The bug seems to be caused by the loop unroller making a pseudo local
> to be able to duplicate it while it is still needed outside of the loop.
> Reverting Eric Botcazou's patch for rtl-optimization/11841, which is
> also about this, fixes the problem.
Thanks for investigating.
> I don't really understand what's going on, but is it possible we still have to
> look at the pseudo luids and not only the note luids? Like this?
IIRC note luids are supposed to be a superset of regular luids, so your check
should be redundant (see regclass.c:reg_scan_mark_refs). Now something could
have invalidated this relationship.
--
What |Removed |Added
----------------------------------------------------------------------------
CC|ebotcazou at gcc dot gnu dot|
|org |
AssignedTo|unassigned at gcc dot gnu |ebotcazou at gcc dot gnu dot
|dot org |org
Status|NEW |ASSIGNED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug rtl-optimization/18577] [3.3 regression] variable use moved before initialization
2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
` (2 preceding siblings ...)
2004-11-21 7:14 ` ebotcazou at gcc dot gnu dot org
@ 2004-11-21 9:07 ` ebotcazou at gcc dot gnu dot org
2004-11-27 16:59 ` cvs-commit at gcc dot gnu dot org
2004-11-27 17:05 ` ebotcazou at gcc dot gnu dot org
5 siblings, 0 replies; 7+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2004-11-21 9:07 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ebotcazou at gcc dot gnu dot org 2004-11-21 09:07 -------
> IIRC note luids are supposed to be a superset of regular luids, so your check
> should be redundant (see regclass.c:reg_scan_mark_refs). Now something could
> have invalidated this relationship.
It's this chunk of code in load_mems:
set = gen_move_insn (reg, best);
set = loop_insn_hoist (loop, set);
if (REG_P (best))
{
for (p = prev_ebb_head; p != loop->start; p = NEXT_INSN (p))
if (REGNO_LAST_UID (REGNO (best)) == INSN_UID (p))
{
REGNO_LAST_UID (REGNO (best)) = INSN_UID (set);
break;
}
}
which changes REGNO_LAST_UID without updating REGNO_LAST_NOTE_UID for pseudo 78.
Note that there is no note mentioning pseudo 78 so REGNO_LAST_NOTE_UID points
to garbage after it is executed.
We could probably update REGNO_LAST_NOTE_UID too here, but there might be other
places with the same problem so I think your proposed fix is the safest one.
I'm going to test it on x86.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug rtl-optimization/18577] [3.3 regression] variable use moved before initialization
2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
` (3 preceding siblings ...)
2004-11-21 9:07 ` ebotcazou at gcc dot gnu dot org
@ 2004-11-27 16:59 ` cvs-commit at gcc dot gnu dot org
2004-11-27 17:05 ` ebotcazou at gcc dot gnu dot org
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu dot org @ 2004-11-27 16:59 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From cvs-commit at gcc dot gnu dot org 2004-11-27 16:59 -------
Subject: Bug 18577
CVSROOT: /cvs/gcc
Module name: gcc
Branch: gcc-3_3-branch
Changes by: ebotcazou@gcc.gnu.org 2004-11-27 16:59:18
Modified files:
gcc : ChangeLog regclass.c regs.h unroll.c
Added files:
gcc/testsuite/gcc.dg: loop-6.c
Log message:
PR optimization/18577
* unroll.c (unroll_loop): Test both REGNO_LAST_UID and
REGNO_LAST_NOTE_UID to decide whether a pseudo is local
to the loop.
Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.16114.2.1027&r2=1.16114.2.1028
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regclass.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.160.4.5&r2=1.160.4.6
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/regs.h.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.26.4.1&r2=1.26.4.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/unroll.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.184.2.9&r2=1.184.2.10
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/loop-6.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=NONE&r2=1.1.4.1
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug rtl-optimization/18577] [3.3 regression] variable use moved before initialization
2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
` (4 preceding siblings ...)
2004-11-27 16:59 ` cvs-commit at gcc dot gnu dot org
@ 2004-11-27 17:05 ` ebotcazou at gcc dot gnu dot org
5 siblings, 0 replies; 7+ messages in thread
From: ebotcazou at gcc dot gnu dot org @ 2004-11-27 17:05 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From ebotcazou at gcc dot gnu dot org 2004-11-27 17:05 -------
See http://gcc.gnu.org/ml/gcc-patches/2004-11/msg02385.html
--
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18577
^ permalink raw reply [flat|nested] 7+ messages in thread
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2004-11-20 16:30 [Bug rtl-optimization/18577] New: [3.3 regression] variable use moved before initialization falk at debian dot org
2004-11-20 16:32 ` [Bug rtl-optimization/18577] " pinskia at gcc dot gnu dot org
2004-11-21 2:33 ` falk at debian dot org
2004-11-21 7:14 ` ebotcazou at gcc dot gnu dot org
2004-11-21 9:07 ` ebotcazou at gcc dot gnu dot org
2004-11-27 16:59 ` cvs-commit at gcc dot gnu dot org
2004-11-27 17:05 ` ebotcazou at gcc dot gnu dot org
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