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* [Bug other/63440] New: -Og does enable -fmerge-constants too
@ 2014-10-02 9:24 rdiezmail-gcc at yahoo dot de
2014-10-06 12:06 ` [Bug other/63440] " rguenth at gcc dot gnu.org
2014-10-06 13:36 ` rdiezmail-gcc at yahoo dot de
0 siblings, 2 replies; 3+ messages in thread
From: rdiezmail-gcc at yahoo dot de @ 2014-10-02 9:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63440
Bug ID: 63440
Summary: -Og does enable -fmerge-constants too
Product: gcc
Version: 4.9.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: rdiezmail-gcc at yahoo dot de
The documentation for -fmerge-constants does not mention that the new
optimization level -Og does enable -fmerge-constants too. Or at least it seems
to do, judging by the generated code size in my tests.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug other/63440] -Og does enable -fmerge-constants too
2014-10-02 9:24 [Bug other/63440] New: -Og does enable -fmerge-constants too rdiezmail-gcc at yahoo dot de
@ 2014-10-06 12:06 ` rguenth at gcc dot gnu.org
2014-10-06 13:36 ` rdiezmail-gcc at yahoo dot de
1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-10-06 12:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63440
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-10-06
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. Do you think it is ok to enable -fmerge-constants with -Og? Note
that the various "Enabled at levels ..." were not updated for -Og.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug other/63440] -Og does enable -fmerge-constants too
2014-10-02 9:24 [Bug other/63440] New: -Og does enable -fmerge-constants too rdiezmail-gcc at yahoo dot de
2014-10-06 12:06 ` [Bug other/63440] " rguenth at gcc dot gnu.org
@ 2014-10-06 13:36 ` rdiezmail-gcc at yahoo dot de
1 sibling, 0 replies; 3+ messages in thread
From: rdiezmail-gcc at yahoo dot de @ 2014-10-06 13:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63440
--- Comment #2 from R. Diez <rdiezmail-gcc at yahoo dot de> ---
Yes, I would enable -fmerge-constants with -Og.
I would do it even for -O0. Merging constants should be safe, and it saves
precious program space when generating debug builds for small embedded targets.
Besides, in my opinion, it does not make sense that the addresses of some
literal strings suddenly change when you enable optimisations, because they get
collapsed. Any bugs because of such shared addresses should be apparent in
debug builds too.
Note that GCC already seems to apply some optimisations when building with -O0.
Specifically, I believe that at least some dead code elimination does occur.
That would make sense, as you do not want to bloat your debug builds
unnecessary.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-10-02 9:24 [Bug other/63440] New: -Og does enable -fmerge-constants too rdiezmail-gcc at yahoo dot de
2014-10-06 12:06 ` [Bug other/63440] " rguenth at gcc dot gnu.org
2014-10-06 13:36 ` rdiezmail-gcc at yahoo dot de
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