[Bug target/126434] [17 Regression] ICE: invalid rtl sharing found in the insn {zero_extendsidi2} since r17-1375

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126434

--- Comment #6 from Konstantinos Eleftheriou <konstantinos.eleftheriou at vrull dot eu> ---
(In reply to Jakub Jelinek from comment #3)
> --- gcc/avoid-store-forwarding.cc.jj	2026-06-05 20:39:09.411516351 +0200
> +++ gcc/avoid-store-forwarding.cc	2026-07-28 11:50:15.835271670 +0200
> @@ -444,7 +444,7 @@ process_store_forwarding (vec<store_fwd_
>        else
>  	move_src = dest;
>  
> -      rtx move = gen_rtx_SET (SET_DEST (load), move_src);
> +      rtx move = gen_rtx_SET (copy_rtx (SET_DEST (load)), move_src);
>  
>        start_sequence ();
>        rtx_insn *insn = emit_insn (move);
> 
> fixes this exact case, but wonder how many other RTX sharing bugs are in the
> pass.
> E.g. dest = SET_DEST (load); and tons of uses of dest in various new insns,
> etc.

Currently there are not any other sharing concerns that I can see,
purely by luck though.

`dest = SET_DEST (load);` passes through `store_bit_field`, which uses
`unshare_all_rtl_in_chain`. The other instances reuse RTX from stores that
are getting deleted. We could use `copy_rtx` for those instances too, just
for hardening.