Re: [PATCH] PR: 19885 [4.0/4.1 Regression] avr dwarf-2 support is broken for head 4.0/4.1

[Björn Haase <bjoern dot m dot haase at web dot de>]

Am Dienstag, 17. Mai 2005 09:07 schrieb Richard Henderson:
> On Tue, May 17, 2005 at 08:08:33AM +0200, Björn Haase wrote:
> > I could provide a more detailed failure report, e.g. post the generated
> > rtx that causes the bootstrap failure when using --with-dwarf2.
>
> I was thinking that there's some portion of dwarf2out that isn't
> using ptr_mode properly.  So I think this may be useful.

Preliminary analysis, of what is causing PR19885:

1.) "dw2_assemble_integer (int size, rtx x)"

is called with 

size == 4 

and 

x == minus:HI (symbol_ref:HI ("*.LELT0")) (symbol_ref:HI ("*.LSLT0")))

. This call itself is generated by 

dw2_asm_output_delta (int size, const char *lab1, const char *lab2,
                      const char *comment, ...)
{
  va_list ap;
    
  va_start (ap, comment);
    
#ifdef ASM_OUTPUT_DWARF_DELTA
  ASM_OUTPUT_DWARF_DELTA (asm_out_file, size, lab1, lab2);
#else
  dw2_assemble_integer (size,
                        gen_rtx_MINUS (Pmode,
                                       gen_rtx_SYMBOL_REF (Pmode, lab1),
                                       gen_rtx_SYMBOL_REF (Pmode, lab2)));

I.e. "dw2_asm_output_delta" passes the parameters size and an expression of 
mode Pmode without checking that they are having the same width.

"dw2_asm_output_delta" itself is called by

static void
output_line_info (void)

and the call reads:

dw2_asm_output_delta (DWARF_OFFSET_SIZE, l2, l1,
                        "Length of Source Line Info");

The problem, therefore always seem to show up, if DWARF_OFFSET_SIZE does not 
correspond to the same width as Pmode.

The patch I have suggested is not affected by the problem since it does not 
use RTL for implementing the calculation of the difference between the two 
lable references but emits the corresponding asm source itself.

Unfortunately, I am lacking the knowledge on how the dwarf2 output generator 
is supposed to behave in order to be able to resolve this issue myself.

Yours,

Björn