Re: Fix g++.dg/torture/stackalign/eh-alloca-1.C with LTO plugin

[Richard Guenther <rguenther at suse dot de>]

On Thu, 2 Dec 2010, Jan Hubicka wrote:

> > 
> > How so?  Maybe via TREE_CONSTANT_POOL_ADDRESS_P stuff?  And why
> 
> The code does not set TREE_CONSTANT_POOL_ADDRESS_P. It does sort of its own constant pool.
> 
> /* Put X, a SYMBOL_REF, in memory.  Return a SYMBOL_REF to the allocated
>    memory.  Differs from force_const_mem in that a single pool is used for
>    the entire unit of translation, and the memory is not guaranteed to be
>    "near" the function in any interesting sense.  IS_PUBLIC controls whether
>    the symbol can be shared across the entire application (or DSO).  *
> 
> As I've explained earlier, the problem is that the code is organized in a way
> first producing label:
> 
>           ASM_GENERATE_INTERNAL_LABEL (label, "LDFCM", dw2_const_labelno);
>           ++dw2_const_labelno;
>           gcc_assert (!maybe_get_identifier (label));
>           decl_id = get_identifier (label);
> 
> (in dw2_force_const_mem)
> Then we happily use decl_id to reffer to the value.
> 
> At the end of compilation dw2_output_indirect_constants build the decl that
> must match the decl_id computed above.  the decl is created as:
> 
> decl = build_decl (UNKNOWN_LOCATION, VAR_DECL, id, ptr_type_node);
> where ID is the DECL_ID produced and used earlier.
> 
> build_decl then store ID in DECL_NAME.  Later DECL_ASSEMBLER_NAME calls
> 
> tree
> decl_assembler_name (tree decl)
> {
>   if (!DECL_ASSEMBLER_NAME_SET_P (decl))
>     lang_hooks.set_decl_assembler_name (decl);
>   return DECL_WITH_VIS_CHECK (decl)->decl_with_vis.assembler_name; 
> }
> 
> and finally we get into
> 
> static void
> lto_set_decl_assembler_name (tree decl)
> {
>   /* This is almost the same as lhd_set_decl_assembler_name, except that
>      we need to uniquify file-scope names, even if they are not
>      TREE_PUBLIC, to avoid conflicts between individual files.  */
>   tree id;
> 
>   if (TREE_PUBLIC (decl))
>     id = targetm.mangle_decl_assembler_name (decl, DECL_NAME (decl));
>   else
>     { 
>       const char *name = IDENTIFIER_POINTER (DECL_NAME (decl));
>       char *label;
> 
>       ASM_FORMAT_PRIVATE_NAME (label, name, DECL_UID (decl));
>       id = get_identifier (label);
>     }
> 
>   SET_DECL_ASSEMBLER_NAME (decl, id);
> }
> 
> I guess LTO frontend might be first one that mangles even names starting with
> '*', but the code above really wants to build a variable with assembler name
> matching internal label produced earlier, so setting assembler name instead of
> going through frontend hooks seems sane to me.
> 
> It would be perhaps bit saner to if we produced decls early, but I am not sure
> I want to reorganize that code now...

Ok, well, at least move setting the assembler name to before we
possibly call DECL_ASSEMBLER_NAME.

Richard.