------- Comment #131 from rguenther at suse dot de 2007-05-23 16:54 -------
Subject: Re: [4.0/4.1/4.2/4.3 Regression] placement
new does not change the dynamic type as it should
On Wed, 23 May 2007, ian at airs dot com wrote:
> ------- Comment #130 from ian at airs dot com 2007-05-23 16:43 -------
> In this example
>
> void foo(int *p)
> {
> float *f = (float *)p;
> new (p) float;
> *f = 1.0;
> }
>
> the pointer is p. In fact the relevant pointer is always the argument to
> placement new, and every pointer which PTA can associate with it.
I don't read that into the semantics of placement new ;) Placement
new doesn't care about the pointer used to refer to the memory it
operates on.
> We may simply have an impasse here. You have a set of rules which will change
> the compiler to support placement new while giving better results for your
> code. I believe that your change will penalize the code I used to work with.
Ok, fair enough. I'll try to teach load-store-motion for loops to not
re-order the inserted stores compared to the order on the loop exit path.
This is the only transformation on the tree-level I came across that
violates my proposed semantics.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29286
