Re: [gimplefe] Parsing PHI functions

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Jun 28, 2016 at 4:16 PM, Prasad Ghangal
<prasad.ghangal@gmail.com> wrote:
> Hi,
>
> For handling PHI, it expects cfg to be built before. So I was
> wondering how are we going to handle this? Do we need to build cfg
> while parsing only?

For handling PHIs we need to have a CFG in the sense that the GIMPLE PHI
data structures are built in a way to have the PHI argument index correspond
to CFG predecessor edge index.  As we'd like to parse phis with args
corresponding
to predecessor block labels, like

a:
  i_1 = 1;
  goto p;

b:
  i_2 = 2;
  goto p;

p:
  i_3 = __PHI (a: i_1, b: i_2);

I think that a possibility is to leave those PHIs as internal function
with label / arg
pairs and have CFG construction lower them to real PHIs.

Of course the parser could as well build a CFG on its own but I think
we should use
the easy way out for now.

Thus you'd have to modify CFG construction a bit to lower the internal
function calls.

Richard.
>
>
>
> Thanks,
> Prasad