Re: Lazy DECL_RTL breakage for weak alias

[Mark Mitchell <mark at codesourcery dot com>]

>>>>> "Jim" == Jim Wilson <wilson@cygnus.com> writes:

    Jim> You can't reproduce it because of your dwarf2out.c patch late
    Jim> last night which was submitted about the same time I
    Jim> submitted my patch.

    Jim> However, that patch "works" by reducing the debug info.  This

On H.J.'s test-case, it produced identical .s files to what GCC 2.95
produced -- without the change, dwarf2out.c was actually trying to
talk about symbols that didn't exist in the generated object file.
Opposite problem, sort-of.

The difference, perhaps, was that his test-case was for an initialized
constant that we perhaps didn't output at all.

I'll look further at your test-case.

    Jim> The problem with the lazy DECL_RTL code is that a NULL
    Jim> DECL_RTL is now ambiguous.  It could mean that the decl is
    Jim> not supposed to have any DECL_RTL.

True.  

However, if we don't have RTL by the time we hit
rtl_for_decl_location, I think we will never need it.  If there's no
RTL, then there's no location -- and we shouldn't be trying to
describe one to the debugger.

    Jim> A possible solution is to state that we must always generate
    Jim> the DECL_RTL before reaching the debug output routines.  We

I agree -- if there's going to be RTL, we must do it by this point.
That's why I used DECL_RTL_IF_SET there.

    Jim> could then fix my testcase by adding a call to make_decl_rtl
    Jim> someplace appropriate, assemble_alias perhaps.  This still
    Jim> needs my make_decl_rtl patch to work though.

Right -- if we really need RTL for this entity.

Thanks for the revised test-case.  I'll look at that.  

What does it mean if something is TREE_PUBLIC, not TREE_STATIC, and
not DECL_EXTERNAL is that always an alias?  That means it has external
linkage, is defined here, but no storage.  One example of such a thing
is a constant (like `const int i = 3;') which me might not output.
But, there's no RTL for something like that.  

It may well be that your patch is correct; I'm just trying to
understand a little better.

All right, I suggest this:

  - Leave in the dwarf2out.c patch.

  - Add in your make_decl_rtl patch.

  - Explicitly call make_decl_rtl in assemble_alias.

How does that sound?

--
Mark Mitchell                   mark@codesourcery.com
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