Re: [tuples] gimple_assign_subcode for GIMPLE_SINGLE_RHS

[Diego Novillo <dnovillo at google dot com>]

On 3/9/08 11:31 AM, Richard Guenther wrote:
> On Sun, Mar 9, 2008 at 3:46 PM, Zdenek Dvorak <rakdver@kam.mff.cuni.cz> wrote:
> > Hi,
> >
> >
> >  > So, what about adding a GIMPLE_COPY code?  The code would have 0
> >  > operands and used only for its numeric value.
> >
> >  another possibility would be to make GIMPLE_COPY an unary operator, and
> >  get rid of the SINGLE_RHS case altogether (of course, unlike any other
> >  unary operator, it would not require its operand to be gimple_val, so
> >  special handling might still be necessary at some places. but it might
> >  be less cumbersome),
>
> I like that.  Maybe I even suggested this some time ago after some
> beer in some IRC
> session.  (I don't see how unary should be fundamentally different from single).

The major difference is that GIMPLE_COPY never exists as a GENERIC tree 
node.  Unary operators do exist in GENERIC.

When converting to GIMPLE, a unary operator will be flattened by putting 
its tree code in gimple_subcode() and its TREE_OPERAND (t, 0) in the RHS.

Instead, a single operand will be put in its entirety in the RHS.  The 
subcode in that case becomes GIMPLE_COPY.  No need to build a one 
operand operator in order to flatten it immediately.


Diego.