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Date: Tue, 09 Aug 2011 16:22:00 -0000
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Subject: Re: Why does a 'new' statement produce so many temporary variables
From: Andrew Pinski <pinskia@gmail.com>
To: Li junsong <ljs.darkfish@gmail.com>
Cc: java@gcc.gnu.org
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On Tue, Aug 9, 2011 at 12:18 AM, Li junsong <ljs.darkfish@gmail.com> wrote:
> =C2=A03. I find that there is no document to describe the implementation =
of
> Java front end.
> =C2=A0=C2=A0=C2=A0=C2=A0 I don't understand why we need so many temporary=
 variables:
>
> =C2=A0=C2=A0=C2=A0=C2=A0 #ref#2#4 =3D _Jv_AllocObjectNoFinalizer (&Number=
.class$$);
> =C2=A0=C2=A0=C2=A0=C2=A0 #ref#3#6 =3D #ref#2#4;
> =C2=A0=C2=A0=C2=A0=C2=A0 #ref#2#4 =3D #ref#3#6;
>
> =C2=A0=C2=A0=C2=A0=C2=A0 Here, the #ref#3#6 and #ref#2#4 is a kind waste.=
 But each "new" statement
> =C2=A0=C2=A0=C2=A0=C2=A0 does the same thing.

The reason is because this is an exact translation of the java
byte-code.  Most source to java byte-code compilers don't do any
optimizations which is why we get a lot of temporary variables here
(this includes the one included with Eclipse which is what GCJ uses as
the source compiler).

Thanks,
Andrew Pinski