I can only reset the pointer ver, not the ivar_occ to invalid the FSA on
this node.
2014-10-14 10:32 GMT+08:00 Yiran Wang <yiran.w...@gmail.com>:
> It sounds like no way to update the alias information. In that case, it
> has to be set to NULL.
> For this specific case here, only the FSA information becomes invalid, I
> think, and is there any way to ignore this part only?
>
> Regards,
> Yiran
>
> On Mon, Oct 13, 2014 at 8:11 AM, Jian-Xin Lai <laij...@gmail.com> wrote:
>
>> Hi,
>>
>> I found a wopt epre/sr bug existing in current open64 trunk.
>>
>> Here is a case:
>> p[0] = expr1;
>> while (1) {
>> temp = p[0]; // A
>> stmts (use of temp)
>> if (...)
>> break;
>> p[4] = expr2; // B
>> p += 4; // C
>> }
>>
>> In FSA phase, the points-to for ILOAD in stmt A is set to
>> "Pointer_is_named_symbol" and the Pointer is "p", Pointer_ver is the index
>> of the VSE entry of p. For stmt A and B, they are not aliased because they
>> have the same "pointer" and different offset.
>>
>> After epre/sr, A is eliminated and a new computation is inserted into the
>> end of loop body:
>> temp = expr1;
>> p[0] = temp;
>> while (1) {
>> stmts (use of temp)
>> if (...)
>> break;
>> p[4] = expr2; // B
>> p += 4; // C
>> temp = p[0]; // A'
>> }
>>
>> The IVAR used in A' was created from A. When rehashing the new IVAR, the
>> Ivar_occ is also copied in Rehash_tree_rec in opt_expr.cxx:
>> 196 if (newcr->Ivar_occ() != NULL)
>> 197
>> newcr->Set_ivar_occ(CXX_NEW(OCC_TAB_ENTRY(*newcr->Ivar_occ()),
>> 198 htable->Sym()->Occ_pool()));
>> 199 else
>> 200 newcr->Set_ivar_occ(NULL);
>>
>> Now both A' and A have the same Ivar_occ. Based on the
>> Aliased_Indirect_Rule, the new ILOAD in A' is still not aliased with the
>> ISTORE B. In later CG phase, the scheduler will reorder A' and B.
>>
>> Here is the question, it looks like it's illegal to copy the Ivar_occ
>> from an existing CR to a new CR considering the case of the Ilod/Istr base
>> is changed. But how can we update the Ivar_occ with precise points-to info?
>> The VSE table has been destroyed when WHIRL is converted into CODEMAP.
>>
>>
>> --
>> Regards,
>> Lai Jian-Xin
>>
>>
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>>
>
--
Regards,
Lai Jian-Xin
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