Re: Don't generate NullPointerExceptions for arraylength and arrayload

[Ranjit Mathew <rmathew at gmail dot com>]

>  > > -  if (type == ptr_type_node)
>  > > -    return build3 (CALL_EXPR, int_type_node,
>  > > -                  build_address_of (soft_nullpointer_node),
>  > > -                  NULL_TREE, NULL_TREE);
>  > > -
>  >
>  > Doesn't doing this make "Array_3 -O3 bytecode -> native"
>  > fail for you?

Now that you've committed it, it does for me.


> No.  We already discussed this in
> http://gcc.gnu.org/ml/gcc-patches/2005-03/msg00465.html.
> 
> I already answered this question in
> http://gcc.gnu.org/ml/gcc-patches/2005-03/msg00746.html

Yes. I'm not that far down the slope of senility yet
to have forgotten such a recent discussion. :-)


> It's possible that the code I removed in this latest patch was
> papering over the real bug, and so Array_3 triggers now where it
> didn't before.

"If a tree falls in a forest and no one hears it,
does it make a sound?" :-)

In other words, if you access a variable and
do not use it, does it not allow an aggressively
optimising compiler to remove the access?
Is this not similar to removing empty loops?

My personal belief is that a compiler should
be allowed to do so and we should put in an
"xfail-at-O3" for this testcase and get on with
our lives.


> I'm interested to know whether people think we should make these loads
> volatile.

IMHO, no. (Though I haven't read the JLS,
JSR-133, etc. carefully for this bit...)

My 2p,
Ranjit.

-- 
Ranjit Mathew      Email: rmathew AT gmail DOT com

Bangalore, INDIA.    Web: http://ranjitmathew.hostingzero.com/