[Bug target/45291] avr miscompilations related to frame pointer registers

[Bug target/45291] avr miscompilations related to frame pointer registers

[avr at gjlay dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45291

Georg Lay <avr at gjlay dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |avr at gjlay dot de

--- Comment #2 from Georg Lay <avr at gjlay dot de> 2010-11-04 16:04:02 UTC ---
insn 34 renders insn 33 invalid. This is due to subreg semantics. There are
several places in several versions of avr backend that use this technique and
will introduce similar bugs that might look different or become visible in
different passes. Amongst them are: 

o bytewise shift
o bytewise rotate
o zero-extending
o bytewise insert
o perhaps many more

Without tracking it down, this particular case semms to be generated by a
zero-extend.

Moreover, there are several optimization flaws that are connected with this
resp. optimization opportunities not implemented yet. As some recrafting will
be needed to fix this anyway, I propose to write the backend so that these
optimization issues will be kicked out (or will vanish without any effort if
patterns are defined appropriately).

As I see Erik CC'ed and I think he has a better overview of bugs/optimization
flaws related to this issue, maybe it's best if he picks one bug and marks the
others as duplicate of it.

[Bug target/45291] avr miscompilations related to frame pointer registers

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45291

--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-04-14 18:50:15 UTC ---
Author: gjl
Date: Thu Apr 14 18:50:02 2011
New Revision: 172442

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=172442
Log:
    PR target/46779
    PR target/45291
    PR target/41894
    * gcc.target/avr/pr46779-1.c: New test case
    * gcc.target/avr/pr46779-2.c: New test case


Added:
    trunk/gcc/testsuite/gcc.target/avr/pr46779-1.c
    trunk/gcc/testsuite/gcc.target/avr/pr46779-2.c
Modified:
    trunk/gcc/testsuite/ChangeLog

[Bug target/45291] avr miscompilations related to frame pointer registers

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45291

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE
   Target Milestone|---                         |4.6.2

--- Comment #4 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-07-08 17:52:08 UTC ---
This is same artifact as PR46779: IRA generates subreg of hard-reg that's not
handled by reload.

*** This bug has been marked as a duplicate of bug 46779 ***

[Bug target/45291] avr miscompilations related to frame pointer registers

[otaylor at redhat dot com]

------- Comment #1 from otaylor at redhat dot com  2010-08-15 20:27 -------
Created an attachment (id=21484)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21484&action=view)
Patch removing the frame pointer from general regs

Here's the patch described; I don't have any sort of extensive framework for
testing the AVR backend - doing such tests would likely be a good idea before
applying this if the general idea is right.

(Patch is git formatted and against 4.5.1 but it should apply to the trunk of
svn fine.)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45291