Re: Incorrect bitfield aliasing with Tree SSA

[Adam Nemet]

Eric Botcazou writes:
> For the Ada testcase:
> 
> ;; s->i = 0
> (insn 7 6 0 p.adb:5 (set (mem/s/j:SI (reg/v/f:DI 59 [ s ]) [4 <variable>.i+0 
> S4 A32])
>         (const_int 0 [0x0])) -1 (nil))
> 
> ;; *p = 1
> (insn 8 7 0 p.adb:6 (set (mem:SI (reg/v/f:DI 60 [ p ]) [2 S4 A32])
>         (const_int 1 [0x1])) -1 (nil))
> 
> ;; return s->i
> (insn 9 8 10 p.adb:6 (set (reg:SI 62)
>         (mem/s/j:SI (reg/v/f:DI 59 [ s ]) [4 <variable>.i+0 S4 A32])) -1 
> (nil))
> 
> i.e. s->i is accessed with the alias set of 'S'.

Thanks, that helped.  I think you're right.  Obviously we don't have
this issue with bitfields in C.

I am trying now to prototype a new approach along the lines of
returning true in component_uses_parent_alias_set for SFT's with
DECL_NONADDRESSABLE_P.

Adam