On Mon, Jan 29, 2024 at 11:29:22PM +0100, Jakub Jelinek wrote:
> On Mon, Jan 29, 2024 at 11:22:44PM +0100, Jakub Jelinek wrote:
> > On Mon, Jan 29, 2024 at 02:01:56PM -0800, H.J. Lu wrote:
> > > > A function accesses a function symbol defined in a comdat group.
> > > > If the function symbol is public, any comdat definition of the same
> > > > group
> > > > signature should provide the function definition. If the function
> > > > symbol
> > > > is private to the comdat group, only functions in the same comdat
> > > > group can access the private function symbol. If a function in a
> > > > different
> > > > comdat group accesses a private symbol, it is a compiler bug and
> > > > link may catch it like in this case.
> > > >
> > >
> > > My patch simply puts the constant pool of the function symbol reference
> > > in the same comdat group as the function definition. I believe it is the
> > > right thing to do.
> >
> > I disagree, I think we should use something like
> > if (current_function_decl)
>
> Or perhaps && DECL_COMDAT_GROUP (current_function_decl) added here as well,
> just to make it change things less often.
>
> > return targetm.asm_out.function_rodata_section (current_function_decl,
> > true);
> >
> > Obviously, for non-reloc or non-pic, we don't want an unconditional
> > if (current_function_decl)
> > return targetm.asm_out.function_rodata_section (current_function_decl,
> > false);
> > that would kill mergeable sections, so perhaps
> > if (current_function_decl
> > && reloc
> > && DECL_COMDAT_GROUP (current_function_decl))
> > return targetm.asm_out.function_rodata_section (current_function_decl,
> > false);
Now, that doesn't actually work, because current_function_decl is always
NULL when the constant pool entries are emitted.
But basing the output section on what it refers rather than what refers to
it seems wrong, plus there is the section anchors support, which treats them
yet differently.
So, I wonder if force_const_mem shouldn't punt if asked to emit from
DECL_COMDAT_GROUP (current_function_decl) a SYMBOL_REF (or CONST PLUS
SYMBOL_REF ...) with the same DECL_COMDAT_GROUP with a private symbol,
or shouldn't punt unless using a per-function (i.e. non-shared) constant
pool, or force a per-function constant pool in that case somehow.
Jakub
