Late SIMPLE_IPA_PASS, DECL_INITIAL and error mark nodes

Late SIMPLE_IPA_PASS, DECL_INITIAL and error mark nodes

[Erick Ochoa]

Hi,

I am looking for a small clarification. I understand that during late
SIMPLE_IPA_PASSes some statically initialized global variables might
have error_mark_node trees in their DECL_INITIAL field.

I believe that I read something similar in the past about how to get
the tree expressions in these situations, and I believe it said one
had to stream in those symbols from the .gnu.lto_.decl section.

However, on the GCC Internals there is also the following mention: "If
the DECL_INITIAL is the error_mark_node, there is an initializer, but
it is given by an explicit statement later in the code; no bitwise
copy is required. " [0]

What (if any) is the correct way to get these expressions?

As a note, when running this pass as an IPA_PASS I am able to see the
DECL_INITIAL node of the variable of interest during LGEN.

Thanks!

[0] https://gcc.gnu.org/onlinedocs/gccint/Working-with-declarations.html

Re: Late SIMPLE_IPA_PASS, DECL_INITIAL and error mark nodes

[Richard Biener]

On Fri, Jun 11, 2021 at 12:07 PM Erick Ochoa via Gcc <gcc@gcc.gnu.org> wrote:
>
> Hi,
>
> I am looking for a small clarification. I understand that during late
> SIMPLE_IPA_PASSes some statically initialized global variables might
> have error_mark_node trees in their DECL_INITIAL field.
>
> I believe that I read something similar in the past about how to get
> the tree expressions in these situations, and I believe it said one
> had to stream in those symbols from the .gnu.lto_.decl section.
>
> However, on the GCC Internals there is also the following mention: "If
> the DECL_INITIAL is the error_mark_node, there is an initializer, but
> it is given by an explicit statement later in the code; no bitwise
> copy is required. " [0]
>
> What (if any) is the correct way to get these expressions?

Use ctor_for_folding (decl) to access a known initializer.  error_mark_node
is returned when there is no known constant initializer, NULL for
zero-init and an actual value otherwise.

> As a note, when running this pass as an IPA_PASS I am able to see the
> DECL_INITIAL node of the variable of interest during LGEN.
>
> Thanks!
>
> [0] https://gcc.gnu.org/onlinedocs/gccint/Working-with-declarations.html