On Thu, Jul 9, 2020 at 8:29 PM David Edelsohn <dje....@gmail.com> wrote:
>
> output_constant_def_contents() can call get_constant_section() with an
> EXP that is a CONSTRUCTOR, which is not a declaration. This can hit
> asserts in GCC machinery to choose a named section for the initialization
> data that expects the parameters to be DECLs.
>
> get_constant_section() is a wrapper around TARGET_ASM_SELECT_SECTION,
> which is documented as:
>
> Return the section into which @var{exp} should be placed. You can
> assume that @var{exp} is either a @code{VAR_DECL} node or a constant of
> some sort.
>
> A CONSTRUCTOR initializer is a "constant of some sort", but isn't
> consistent with DECL_SECTION_NAME, etc.
>
> This patch changes get_constant_section() and its callers to pass the
> DECL within the EXP instead of the EXP, and to explicitly pass the reloc
> information that must be determined from the EXP.
>
> Another option is to remove get_constant_section() completely, replace
> it with direct calls to targetm.asm_out.select_section() (for which it
> now is a complete pass-through), and update the Target Hook
> documentation.
>
> What's the preferred path forward?
Given we can always pass a decl - in the cases you change the former
parameter is simply DECL_INITIAL of the now passed decl - this is
a welcome cleanup of the TARGET_ASM_SELECT_SECTION
interface and it should be amended with adjusting its documentation.
That in turn might be an opportunity to cleanup target code.
I think we cannot rule out that targets special-case say STRING_CST
but not DECL_INITIAL (decl) == STRING_CST so some kind of
auditing is probably required.
David - I know you need this for AIX - I think the target hook implementation
is supposed to assume that if it doesn't get passed a decl then it's
a "random constant" without any special attributes attached. What's
your requirement that can possibly only be fulfilled with seeing a decl?
Richard.
> Thanks, David
>
> gcc/ChangeLog
>
> 2020-07-09 David Edelsohn <dje....@gmail.com>
>
> * varasm.c (get_constant_section): Change first parameter from
> EXP to DECL and insert reloc second parameter.
> (build_constant_desc): Adjust call.
> (output_constant_def_contents): Adjust call.
