[Bug ipa/90401] Missed propagation of by-ref constant argument to callee function

[fxue at os dot amperecomputing.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90401

--- Comment #2 from Feng Xue <fxue at os dot amperecomputing.com> ---
(In reply to Richard Biener from comment #1)
> Huh.  IPA-CP dump difference:
> 
> @@ -26,6 +26,8 @@
>           Unknown VR
>      callsite  int caller(int, int&)/2 -> int callee(int&)/1 : 
>         param 0: UNKNOWN
> +         Aggregate passed by reference:
> +           offset: 0, cst: 1
>           value: 0x0, mask: 0xfffffffffffffffc
>           VR  ~[0, 0]
>    Jump functions of caller  int callee(int&)/1:

This jump function is for the 2nd call. For the 1st call, IPA-CP can not deduce
that. So there is no enough benefit to convince IPA-CP to clone the "callee()".

> 
> I guess somehow IPA-CP walks stmts for defs instead of virtual operands?

Yes, it is. IPA-CP only walks stmts in callsite basic block.