Re: [PATCH 1/2] select .rodata for const volatile variables.

[Cupertino Miranda <cupertino.miranda@oracle.com>]

Richard Biener writes:

> On Mon, Dec 5, 2022 at 7:07 PM Jeff Law via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>>
>>
>>
>> On 12/2/22 10:52, Cupertino Miranda via Gcc-patches wrote:
>> > Changed target code to select .rodata section for 'const volatile'
>> > defined variables.
>> > This change is in the context of the bugzilla #170181.
>> >
>> > gcc/ChangeLog:
>> >
>> >       v850.c(v850_select_section): Changed function.
>> I'm not sure this is safe/correct.  ISTM that you need to look at the
>> underlying TREE_TYPE to check for const-volatile rather than
>> TREE_SIDE_EFFECTS.
>
> Just to quote tree.h:
>
> /* In any expression, decl, or constant, nonzero means it has side effects or
>    reevaluation of the whole expression could produce a different value.
>    This is set if any subexpression is a function call, a side effect or a
>    reference to a volatile variable.  In a ..._DECL, this is set only if the
>    declaration said `volatile'.  This will never be set for a constant.  */
> #define TREE_SIDE_EFFECTS(NODE) \
>   (NON_TYPE_CHECK (NODE)->base.side_effects_flag)
>
> so if exp is a decl then that's the volatile check.
>

Thank you Richard for the review.
Jeff: Can you please let me know if Richard comments reply to your
concerns?

Cupertino

>> Of secondary importance is the ChangeLog.  Just saying "Changed
>> function" provides no real information.  Something like this would be
>> better:
>>
>>         * config/v850/v850.c (v850_select_section): Put const volatile
>>         objects into read-only sections.
>>
>>
>> Jeff
>>
>>
>>
>>
>> > ---
>> >   gcc/config/v850/v850.cc | 1 -
>> >   1 file changed, 1 deletion(-)
>> >
>> > diff --git a/gcc/config/v850/v850.cc b/gcc/config/v850/v850.cc
>> > index c7d432990ab..e66893fede4 100644
>> > --- a/gcc/config/v850/v850.cc
>> > +++ b/gcc/config/v850/v850.cc
>> > @@ -2865,7 +2865,6 @@ v850_select_section (tree exp,
>> >       {
>> >         int is_const;
>> >         if (!TREE_READONLY (exp)
>> > -       || TREE_SIDE_EFFECTS (exp)
>> >         || !DECL_INITIAL (exp)
>> >         || (DECL_INITIAL (exp) != error_mark_node
>> >             && !TREE_CONSTANT (DECL_INITIAL (exp))))