Re: PR41357: libgomp broken debug info vs. TLS emu

[Dave Korn <dave dot korn dot cygwin at googlemail dot com>]

Dave Korn wrote:
>     Hi all, and Ping! Alex :)
> 
>   Since the recent vta changes, libgomp build seems to be broken on at least
> some platforms that rely on tls emulation.  All references to tls variables in
> the generated source are prefixed with "__emutls_v" by the action of
> get_emutls_object_name() in varasm.c, but the debug information ends up with a
> reference to the un-prefixed original version of the variable's name.

  The problem appears to lie in the generation of the NOTE_VAR_LOCATION for a
local variable in the affected function:

> (gdb) call debug_tree(0x7fe190c0)
>  <var_decl 0x7fe190c0 gomp_tls_data
>     type <record_type 0x7fe7df90 gomp_thread asm_written type_0 BLK
>         size <integer_cst 0x7fe2a8e0 constant 416>
>         unit size <integer_cst 0x7fe87dc0 constant 52>
>         align 32 symtab 2145789512 alias set 7 canonical type 0x7fe7df90
>         fields <field_decl 0x7fe18ca0 fn type <pointer_type 0x7fda5e10>
>             unsigned SI file /gnu/gcc/gcc/libgomp/libgomp.h line 327 col 10
>             size <integer_cst 0x7fef0580 constant 32>
>             unit size <integer_cst 0x7fef0320 constant 4>
>             align 32 offset_align 128
>             offset <integer_cst 0x7fef0340 constant 0>
>             bit offset <integer_cst 0x7fef0b60 constant 0> context <record_type 0x7fe7df90 gomp_thread> chain <field_decl 0x7fe18d00 data>> context <translation_unit_decl 0x7fcac550 D.3329>
>         pointer_to_this <pointer_type 0x7fe7e230> chain <type_decl 0x7fe7e000 D.2396>>
>     addressable used public external tls-local-exec BLK file /gnu/gcc/gcc/libgomp/libgomp.h line 361 col 36 size <integer_cst 0x7fe2a8e0 416> unit size <integer_cst 0x7fe87dc0 52>
>     align 32
>     (mem/s/c:BLK (symbol_ref:SI ("gomp_tls_data") [flags 0x42] <var_decl 0x7fe190c0 gomp_tls_data>) [7 gomp_tls_data+0 S52 A32]) chain <function_decl 0x7fdfb000 gomp_new_icv>>
> (gdb)

  Notice that in this var_decl, the DECL_TLS_MODEL is "tls-local-exec", but
this is not reflected in the RTL, which has no tls model set in bits 3:5 of
the flags.  I'm now about to start digging into where this note is created; as
before, if anyone has any pointers or theories, that would really help speed
me on my way.

    cheers,
      DaveK