* [Bug lto/44150] [4.6 regression] g++.dg/lto/20081109 cp_lto_20081109_0.o-cp_lto_20081109_1.o
2010-05-15 13:59 [Bug middle-end/44150] New: " hjl dot tools at gmail dot com
@ 2010-05-15 22:50 ` jason at gcc dot gnu dot org
2010-05-15 23:04 ` steven at gcc dot gnu dot org
` (4 subsequent siblings)
5 siblings, 0 replies; 11+ messages in thread
From: jason at gcc dot gnu dot org @ 2010-05-15 22:50 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from jason at gcc dot gnu dot org 2010-05-15 22:49 -------
OK, here's what's going wrong:
The LTO design is such that EH is only enabled if we encounter a function with
an EH personality.
With -fwhopr we process one translation unit at a time, so when we look at
20081109_1.C we only see foo(int).
Before my patch foo(int) contained an ERT_MUST_NOT_THROW region, so we required
the C++ personality function. After my patch, it contains an ERT_CLEANUP
region instead, which doesn't require the C++ personality function
So cgraph doesn't set DECL_FUNCTION_PERSONALITY, so lto1 doesn't think that foo
needs EH, so it never sets flag_exceptions, so we don't get unwind information,
so the throw can't unwind through foo.
There seem to be two issues here:
1) lto1 incorrectly thinks foo doesn't need EH.
2) -fwhopr means that lto1 can make different decisions about EH for different
translation units, so things blow up when linked together.
With #2 fixed, #1 isn't as big a problem--but it could still be an issue if we
aren't compiling the entire program, i.e. a shared library wants to throw from
a callback. If anything we call can throw, we need unwind information and
should turn on -fexceptions.
--
jason at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|jason at gcc dot gnu dot org|unassigned at gcc dot gnu
| |dot org
Status|ASSIGNED |NEW
Component|middle-end |lto
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44150
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug lto/44150] [4.6 regression] g++.dg/lto/20081109 cp_lto_20081109_0.o-cp_lto_20081109_1.o
2010-05-15 13:59 [Bug middle-end/44150] New: " hjl dot tools at gmail dot com
2010-05-15 22:50 ` [Bug lto/44150] " jason at gcc dot gnu dot org
@ 2010-05-15 23:04 ` steven at gcc dot gnu dot org
2010-05-16 10:56 ` rguenth at gcc dot gnu dot org
` (3 subsequent siblings)
5 siblings, 0 replies; 11+ messages in thread
From: steven at gcc dot gnu dot org @ 2010-05-15 23:04 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from steven at gcc dot gnu dot org 2010-05-15 23:04 -------
Why is flag_exceptions not just streamed out/in with other options?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44150
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug lto/44150] [4.6 regression] g++.dg/lto/20081109 cp_lto_20081109_0.o-cp_lto_20081109_1.o
2010-05-15 13:59 [Bug middle-end/44150] New: " hjl dot tools at gmail dot com
2010-05-15 22:50 ` [Bug lto/44150] " jason at gcc dot gnu dot org
2010-05-15 23:04 ` steven at gcc dot gnu dot org
@ 2010-05-16 10:56 ` rguenth at gcc dot gnu dot org
2010-05-16 10:59 ` rguenth at gcc dot gnu dot org
` (2 subsequent siblings)
5 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-05-16 10:56 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from rguenth at gcc dot gnu dot org 2010-05-16 10:56 -------
(In reply to comment #3)
> Why is flag_exceptions not just streamed out/in with other options?
It is, but the option merging is basically broken by design (and comes too
late anyway).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44150
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug lto/44150] [4.6 regression] g++.dg/lto/20081109 cp_lto_20081109_0.o-cp_lto_20081109_1.o
2010-05-15 13:59 [Bug middle-end/44150] New: " hjl dot tools at gmail dot com
` (2 preceding siblings ...)
2010-05-16 10:56 ` rguenth at gcc dot gnu dot org
@ 2010-05-16 10:59 ` rguenth at gcc dot gnu dot org
2010-05-26 12:12 ` rguenth at gcc dot gnu dot org
2010-09-02 10:47 ` rguenth at gcc dot gnu dot org
5 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-05-16 10:59 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2010-05-16 10:58 -------
(In reply to comment #2)
> OK, here's what's going wrong:
>
> The LTO design is such that EH is only enabled if we encounter a function with
> an EH personality.
>
> With -fwhopr we process one translation unit at a time, so when we look at
> 20081109_1.C we only see foo(int).
>
> Before my patch foo(int) contained an ERT_MUST_NOT_THROW region, so we required
> the C++ personality function. After my patch, it contains an ERT_CLEANUP
> region instead, which doesn't require the C++ personality function
>
> So cgraph doesn't set DECL_FUNCTION_PERSONALITY, so lto1 doesn't think that foo
> needs EH, so it never sets flag_exceptions, so we don't get unwind information,
> so the throw can't unwind through foo.
>
> There seem to be two issues here:
> 1) lto1 incorrectly thinks foo doesn't need EH.
> 2) -fwhopr means that lto1 can make different decisions about EH for different
> translation units, so things blow up when linked together.
>
> With #2 fixed, #1 isn't as big a problem--but it could still be an issue if we
> aren't compiling the entire program, i.e. a shared library wants to throw from
> a callback. If anything we call can throw, we need unwind information and
> should turn on -fexceptions.
2) should be fixed by deciding on EH info at WPA stage (and not re-deciding
at LTRANS stage for every translation unit).
The current way of detecting whether to init EH is somewhat of a hack, and
there is no convenient place to store such overall properties (no, the
current option saving/restoring machiner is not it).
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hubicka at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44150
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug lto/44150] [4.6 regression] g++.dg/lto/20081109 cp_lto_20081109_0.o-cp_lto_20081109_1.o
2010-05-15 13:59 [Bug middle-end/44150] New: " hjl dot tools at gmail dot com
` (3 preceding siblings ...)
2010-05-16 10:59 ` rguenth at gcc dot gnu dot org
@ 2010-05-26 12:12 ` rguenth at gcc dot gnu dot org
2010-09-02 10:47 ` rguenth at gcc dot gnu dot org
5 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-05-26 12:12 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from rguenth at gcc dot gnu dot org 2010-05-26 12:11 -------
Mine.
--
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|2010-05-15 21:40:13 |2010-05-26 12:11:52
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44150
^ permalink raw reply [flat|nested] 11+ messages in thread* [Bug lto/44150] [4.6 regression] g++.dg/lto/20081109 cp_lto_20081109_0.o-cp_lto_20081109_1.o
2010-05-15 13:59 [Bug middle-end/44150] New: " hjl dot tools at gmail dot com
` (4 preceding siblings ...)
2010-05-26 12:12 ` rguenth at gcc dot gnu dot org
@ 2010-09-02 10:47 ` rguenth at gcc dot gnu dot org
5 siblings, 0 replies; 11+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-09-02 10:47 UTC (permalink / raw)
To: gcc-bugs
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44150
^ permalink raw reply [flat|nested] 11+ messages in thread