https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106075
--- Comment #11 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Eric, maybe you can help with RTL DSE here?
The problem is that add_non_frame_wild_read is exclusive, i.e. the read is
turned into a read from *only* non-frame memory, but can_throw_external
is conservative and may return true for a read from frame memory:
(insn 15 13 16 4 (set (reg:QI 87 [ _20 ])
(mem:QI (plus:DI (reg/f:DI 100)
(reg:DI 92 [ ivtmp.23 ])) [8 MEM <character>
[(interfaces__unsigned_32 *)&value.4 + ivtmp.23_39 * 1]+0 S1 A8]))
"opt47.adb":22:13 91 {*movqi_internal}
value.4 is a local variable but can_throw_external return true on the read.
So you would need to implement an inclusive version of add_non_frame_wild_read
but the change is going to pessimize Ada and Go if the condition to invoke it
is not made more precise.
