[Bug c/28306] New: const / pure call with ignored argument emitted.

[Bug c/28306] New: const / pure call with ignored argument emitted.

[amylaar at gcc dot gnu dot org]

There is code in the expanders which is supposed to avoid emitting calls
to pure functions which have their result ignored, but it doesn't appear to
work when the function called is represented as a COND_EXPR.


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           Summary: const / pure call with ignored argument emitted.
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: amylaar at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu
OtherBugsDependingO 28289
             nThis:


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28306

[Bug c/28306] const / pure call with ignored argument emitted.

[amylaar at gcc dot gnu dot org]

------- Comment #1 from amylaar at gcc dot gnu dot org  2006-07-07 16:54 -------
Created an attachment (id=11850)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11850&action=view)
test case

The available source code for the functions allows the compiler to
see that the called functions are const.
This should be sufficient for the compiler to figure out the call is not
needed.
Likewise, the pure attributes should also be sufficient to figure this out.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28306

[Bug c/28306] const / pure call with ignored argument emitted.

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2006-07-07 17:30 -------
Confirmed.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-07-07 17:30:13
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28306

[Bug c/28306] const / pure call with ignored argument emitted.

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2008-01-13 18:22 -------
This works for 'const' functions because they stick on the function type as
well.
The attributes are only on the DECL and do not get merged and transfered to the
resulting function type of the COND_EXPR.

So this again asks for streamlining attributes on types vs. decls.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28306