[tree-ssa] Gimplifying Java

[Jeff Sturm]

On 13 Jun 2003, Diego Novillo wrote:
> On Fri, 2003-06-13 at 17:17, Jeff Sturm wrote:
> > On Fri, 13 Jun 2003, Andrew Haley wrote:
> > > Is this one right?  I thought the copy-in and out of the temporary was
> > > necessary on some architectures.
> >
> > I expected these to be equivalent.  There's still a temporary involved.
> > The trouble with the old code is that a VAR_DECL all by itself doesn't
> > appear to be a valid GIMPLE expression and causes some odd looking tree
> > dumps.
> >
> Does the java gimplifier generate a GIMPLE statement that is nothing but
> a VAR_DECL?  That is not good (and we should probably have a check to
> ICE early)

It did.  I had changed the equivalent of:

  t = {int <tmp>; <tmp> = p->a; <tmp>}

to:

  t = {int <tmp>; <tmp> = p->a;}

Andrew Haley says the latter might produce different code, and I suspect
he's right.  The idea is to not overwrite t if deferencing p causes an
exception.

That said, I'm not sure how to correctly express the former in GIMPLE,
without introducing another temporary.

Jeff