> From: Berin Loritsch [mailto:[EMAIL PROTECTED]
>
> J�rg Schaible wrote:
>
> >
> > Sure? I would suppose, that an object is created and
> directly handed
> > over to the GC. Otherwise the Compiler must have knowledge of the
> > (possibly empty) implementation of any inherited c'tors.
> >
>
> All I am saying is that optimizing compilers look at things
> like initializing variables that will never be used, and then
> remove them from use. Very few people have constructors that
> have side-effects outside of the actual object that they are
> using. I would call it a bug if they did.
>
> All that aside, it would be a legal optimization for the
> compiler to make to strip out the contents of the loop and
> merely compile an empty loop. If the compiler doesn't do it,
> then the HotSpot VM sure will.
Classic example is a loop that strobes a memory-mapped port
(C++ code below):
char* port = (char*) 0x1000;
*port = 0;
for (int i = 0; i < 10; i++)
{
*port = 1;
*port = 0;
}
Since the value of *port is unchanged by the whole loop, the
loop can be reduced to:
char* port = (char*) 0x1000;
*port = 0;
for (int i = 0; i < 10; i++)
{
}
And then the compiler can remove the loop altogether and
feel really good about how clever it was:
char* port = (char*) 0x1000;
*port = 0;
But that wasn't really what the programmer intended.
/LS
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