https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111591
--- Comment #24 from Kewen Lin <linkw at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #22)
> I see the mems properly get their base adjusted:
>
> (insn 384 383 0 (set (mem/c:V2DI (plus:DI (reg/f:DI 112 virtual-stack-vars)
> (const_int 16 [0x10])) [7 MEM[(struct Vec128D.30433 *)_10]+0
> S16 A128])
> (reg:V2DI 616)) -1
> (nil))
>
> vs.
>
> (insn 389 388 390 (set (reg:HI 619)
> (mem/c:HI (plus:DI (reg/f:DI 112 virtual-stack-vars)
> (const_int 16 [0x10])) [4 MEM[(struct Vec128D.30212
> *)_10].rawD.30221[0]+0 S2 A128])) "test.cc":218:14 -1
> (nil))
>
> both are based off a fake _10. But we get alias sets 7 and 4 used here
> which might be a problem.
>
> See update_alias_info_with_stack_vars and uses of decls_to_pointers,
> in particular from set_mem_attributes_minus_bitpos where we preserve
> TBAA info with the rewrite. I'm not sure why that should be OK ...
> (but I'm sure I must have thought of this problem back in time)
>
> Does the following fix the testcase?
>
> diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
> index 84b6833225e..81c0a63eddc 100644
> --- a/gcc/emit-rtl.cc
> +++ b/gcc/emit-rtl.cc
> @@ -2128,7 +2128,7 @@ set_mem_attributes_minus_bitpos (rtx ref, tree t, int
> objectp,
> tree *orig_base = &attrs.expr;
> while (handled_component_p (*orig_base))
> orig_base = &TREE_OPERAND (*orig_base, 0);
> - tree aptrt = reference_alias_ptr_type (*orig_base);
> + tree aptrt = ptr_type_node;
> *orig_base = build2 (MEM_REF, TREE_TYPE (*orig_base), *namep,
> build_int_cst (aptrt, 0));
> }
Sorry, this doesn't help.
I noticed that it makes insns 384 and 389 become to:
(insn 384 383 0 (set (mem/c:V2DI (plus:DI (reg/f:DI 112 virtual-stack-vars)
(const_int 16 [0x10])) [7 MEM <struct Vec128D.30433> [(voidD.48
*)_10]+0 S16 A128])
(reg:V2DI 616)) -1
(nil))
(insn 389 388 390 (set (reg:HI 619)
(mem/c:HI (plus:DI (reg/f:DI 112 virtual-stack-vars)
(const_int 16 [0x10])) [4 MEM <struct Vec128D.30212> [(voidD.48
*)_10].rawD.30221[0]+0 S2 A128])) "test.cc":218:14 -1
(nil))
alias sets are not changed. Aggressively further hacking with attrs.alias = 0
can make it pass. Can we make an new alias set for each partition? then all
involved decls in the same partition is aliased. For a particular involved
decl, it's aliased to the previous ones and the new ones in its own partitions.
