Re: Performing inter-procedural dataflow analysis

[Martin Jambor <mjambor@suse.cz>]

Hi,

On Thu, Feb 18 2021, Shuai Wang via Gcc wrote:
> Hello,
>
> I am doing interprocedural dataflow analysis and countered the following
> issue. Suppose I have an GIMPLE IR code as follows, which is after the
> "simdclone" pass while before my own SIMPLE IPA pass:
>
>
> foo (int a, int b)
> {
>   int c;
>   int d;
>   int D.2425;
>   int _5;
>
>   <bb 2> :
> *  c_4 = a_2(D) + b_3(D);  *
> *  _5 = c_4;*
>   ....
>
> As you can see, while propagating certain dataflow facts among local
> variables are smooth (e.g., from c_4 --> c_4 --> _5), I can hardly somehow
> "link" function parameter "a" (or "b") with its first local usage "a_2(D)"
> or "b_3(D)".

are you perhaps looking for function ssa_default_def (defined in tree-dfa.c)?

>
> So my question is, when traversing the GIMPLE statements and encounter SSA
> variables like "a_2(D)" or "b_3(D)", how do I know they originate from
> parameter "a" and "b"?

You check that SSA_NAME_IS_DEFAULT_DEF is true (and that their
SSA_NAME_VAR is the PARM_DECL you are after).

Martin