[PATCH] Adjust subprogram DIE re-usal

[Jeff Law]

On 06/26/2018 06:43 AM, Richard Biener wrote:
> 
> A patch from Honza not LTO streaming DECL_ORIGINAL_TYPE ends up
> ICEing during LTO bootstrap because we end up not re-using the
> DIE we create late during LTRANS for a subprogram because its
> parent is a namespace rather than a CU DIE (or a module).
> 
> I'm wondering of the general reason why we enforce (inconsistently)
> "We always want the DIE for this function that has the *_pc attributes to 
> be under comp_unit_die so the debugger can find it."
> We indeed generate a specification DIE rooted at the CU in addition to the
> declaration DIE inside the namespace for sth as simple as
> 
> namespace Foo { void foo () {} }
> 
> anyhow - the comment also says "We also need to do this [re-use the DIE]
> for abstract instances of inlines, since the spec requires the out-of-line
> copy to have the same parent.".  Not sure what condition this part of
> the comment applies to.
> 
> So my fix is to move the || get_AT (old_die, DW_AT_abstract_origin)
> check I added for early LTO debug to a global override - forcing
> DIE re-use for any DIE with an abstract origin set.  That is, all
> concrete instances are fine where they are.  That also avoids
> double-indirection DW_AT_specification -> DW_AT_abstract_origin -> DIE.
> 
> But as said, I wonder about the overall condition, esp. the
> DW_TAG_module special-casing (but not at the same time
> special-casing DW_TAG_namespace or DW_TAG_partial_unit).
> 
> LTO bootstrap is in progress on x86_64-unknown-linux-gnu.
> 
> OK if that succeeds?
> 
> Thanks,
> Richard.
> 
> 2018-06-26  Richard Biener  <rguenther@suse.de>
> 
> 	* dwarf2out.c (gen_subprogram_die): Always re-use DIEs with an
> 	DW_AT_abstract_origin attribute.
Explicitly deferring to Jason here.

jeff