[Bug java/17187] New: Call to java.lang.Object constructor is redundant

[Bug java/17187] New: Call to java.lang.Object constructor is redundant

[mckinlay at redhat dot com]

The constructor for java.lang.Object does nothing. Its probably a reasonable
assumption that it will always do nothing, so, we should change the compiler to
not generate calls to it when generating native code. This would save 1 call for
every "new" operation, and also improve the number of inlining opportunities
available to the compiler, as many constructor calls could now be fully inlined.

One way to do this might be to extend the java "builtins" mechanism to allow us
to  turn other well known calls, not just Math.* calls, into inlined trees. If
we see a java.lang.Object() call, check_for_builtin() would just return an empty
statement tree.

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           Summary: Call to java.lang.Object constructor is redundant
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: java
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mckinlay at redhat dot com
                CC: gcc-bugs at gcc dot gnu dot org,java-prs at gcc dot gnu
                    dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17187

[Bug java/17187] Call to java.lang.Object constructor is redundant

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-08-25 15:58 -------
Confirmed.  But I should note that even the Sun's javac does not do this optimization so ...

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           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-08-25 15:58:47
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17187

[Bug java/17187] Call to java.lang.Object constructor is redundant

[mckinlay at redhat dot com]

------- Additional Comments From mckinlay at redhat dot com  2004-08-25 16:16 -------
pinskia: bytecode compilation is a different story. Obviously we should only do
this when compiling to _native_ code. We know our java.lang.Object constructor
doesn't do anything, but we can't make that assumption about other implementations.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17187

[Bug java/17187] Call to java.lang.Object constructor is redundant

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-08 02:49 -------
Man this is a semi hard problem, I could figure out where the call expression is built but we patch it up 
which makes it harder (maybe we should pass a pointer to the tree which we patch up and then change 
it to a nop).

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17187