On Fri, Apr 5, 2024 at 3:44 PM Pierrick Philippe
<pierrick.phili...@irisa.fr> wrote:
>
> On 05/04/2024 14:46, Richard Biener wrote:
>
> On Fri, Apr 5, 2024 at 1:59 PM Pierrick Philippe
> <pierrick.phili...@irisa.fr> wrote:
>
> Hi all,
>
> I do have a question regarding ssa_name and result_decl.
>
> For example on the following gimple function:
>
> int f ()
> {
> int x;
> int D.2747;
> int _2;
>
> <bb 2> :
> x_1 = 42;
> _2 = x_1;
>
> <bb 3> :
> <L0>:
> return _2;
>
> }
>
> On the above example, using the macro SSA_NAME_VAR() on _2 does not
> yield anything usable.
> Neither to call ssa_default_def() on the result of the result_decl
> obtain through macro DECL_RESULT().
>
> Is there a way to get the ssa_name corresponding to the result_decl of a
> function obtained through the use of macro DECL_RESULT() on a fn_decl?
> And/or the other way around? I.e., from the returned ssa_name of a
> function to the result_decl of that function?
>
> I totally might be missing something here, but I cannot figure out what.
>
> DECL_RESULT isn't always used (as in your example). Not all SSA names
> have corresponding declarations, we have "anonymous" SSA names which
> have a NULL_TREE SSA_NAME_VAR (such as the _2 in your example).
>
> I see, that makes so much more sense to me now.
>
> What do you try to find in the end? If you want to find all returns you can
> walk predecessors of EXIT_BLOCK and look at their last stmt whether they
> are greturn statements.
>
> I am implementing a state_machine within the analyzer, and I am trying to
> understand where would be the best place to propagate the state of the return
> value.
> I intuitively thought it would be best to do so in the
> state_machine::on_pop_frame() method, which is called by the analyzer between
> the two frames of the caller and the callee. What I do have access to is the
> struct function of the callee/caller, the gcall instruction in the caller and
> the callee have been processed by my analysis.
It might make sense to record the analysis of the return value in
meta-data that the analyzer keeps and access it that way.
Other than that you'd have to do it the way I said with finding the
greturn stmts again and look at what is returned there.
> And to illustrate, here I do have the _2 ssa_name and its state which I know
> in that case should be propagate to the lhs of the caller gcall instruction.
>
> Again I might be taking this in a wrong way.
>
> Richard.
>
> Thanks for your time,
>
> Pierrick
