Re: [V4 00/21] Fortran dynamic array support

[Bernhard Heckel <bernhard.heckel@intel.com>]

On 16/08/2016 15:59, Jan Kratochvil wrote:
> Hi Bernhard,
>
> On Tue, 09 Aug 2016 09:55:05 +0200, Heckel, Bernhard wrote:
>> I took a look at "p varw" issue.
>>
>> >From my point of view, the debug information for  the location of varw is wrong.
>>
>> Set a breakpoint at line 68 and run.
>> "P &varw" in GDB gives me same location as the print of "loc(z(2,4,6))" out of the fortran testcase.
>> Nevertheless, "loc(varw)" shows me a different location. Investigating on the dwarf debug info, GDB address calculation
>> of "varw" is correct. From my point of view, the location expression of "varw" is wrong.
>>
>> If you manual examine the content at "loc(varw)" you see the right content.
>>
>> FYI: I added a variable "dummy" in subroutine "foo" in order to get the content of fbreg and do manual address calculation.
>>
>> I attached the testcase + dwarf
> primarily Fedora 24 GDB (and many Fedora releases back) - with the older Intel
> VLA patch series - does PASS the testcase fine with gfortran DWARF so
> completely wrong the DWARF is not.
>
> Also you talk here only about starting address of 'varw'.  But that is not
> a problem, the starting address in inferior + in GDB do match:
>    varw(1, 1, 1) = 6
> vs.
> $23 = (( ( 6, 5, 1, 5, 5) ( 3, 3, 3, 5, 5) ( 5, 5, 5, 3, 3) ( 3, 5, 5, 5, 5) ) ( ( 5, 3, 3, 3, 5) ( 5, 5, 5, 5, 3) ( 3, 3, 3, 3, 3) ( 3, 3, 3, 3, 3) ) ( ( 3, 3, 3, 3, 3) ( 3, 3, 3, 3, 3) ( 3, 3, 3, 3, 3) ( 3, 3, 3, 3, 3) ) )
> (gdb) FAIL: gdb.fortran/dynamic.exp: p varw filled
>   - the value 6 is really the first (1,1,1) value printed.
> The starting address is nothing special for GDB as starting address is
> adjusted/offseted by the inferior caller, GDB just reads the inferior-computed
> address.
>
> What is wrong is accessing 'varw' elements not in the first row of the array
> by GDB - because GDB needs to know the stride for it.
> Stride is described there in DWARF:
>      <231>   DW_AT_upper_bound : 11 byte block: 31 97 23 28 6 97 23 20 6 1c 22   (DW_OP_lit1; DW_OP_push_object_address; DW_OP_plus_uconst: 40; DW_OP_deref; DW_OP_push_object_address; DW_OP_plus_uconst: 32; DW_OP_deref; DW_OP_minus; DW_OP_plus)
>      <23d>   DW_AT_byte_stride : 6 byte block: 97 23 18 6 34 1e  (DW_OP_push_object_address; DW_OP_plus_uconst: 24; DW_OP_deref; DW_OP_lit4; DW_OP_mul)
> and that just fetches the values from gfortran array descriptor - otherwise the
> inferior Fortran function 'foo' would not work.
>
> Why do you think gfortran has the DWARF wrong?  Do your GDB patches PASS with
> ifort?  I no longer have ifort - I got a license from Markus Metzger many
> years ago, it was somehow complicated in Intel to get it for me and the
> license laster only one year.  You would have to send me the ifort-built
> binary (or .s file).
>
>
> I have tried now to re-apply a part of the old working Intel VLA patch of
> value_subscripted_rvalue():
>     unsigned int elt_size = TYPE_LENGTH (elt_type);
> -  unsigned int elt_offs = elt_size * longest_to_int (index - lowerbound);
> +  unsigned int elt_offs = longest_to_int (index - lowerbound);
> +  LONGEST elt_stride = TYPE_BYTE_STRIDE (TYPE_INDEX_TYPE (array_type));
>     struct value *v;
>
> +  if (elt_stride > 0)
> +    elt_offs *= elt_stride;
> +  else if (elt_stride < 0)
> +    {
> +      int offs = (elt_offs + 1) * elt_stride;
> +
> +      elt_offs = TYPE_LENGTH (array_type) + offs;
> +    }
> +  else
> +    elt_offs *= elt_size;
> +
>
> But it does not work (attached).  Maybe because the stride of an array now
> appears to be stored into TYPE_FIELD_BITSIZE of the array itself (not its type)
> while with old Intel VLA patchset there was a special field TYPE_BYTE_STRIDE
> for that.
>
>
> Thanks,
> Jan
Hi Jan,

here is the missing patch in your environment.
https://sourceware.org/ml/gdb-patches/2015-01/msg00385.html
This patch handles strides in DWARF and your fortran program.

Christoph's patch series was about strides in user input, for example 
"print my_vla(1:10:2)"

I will create a branch about all stride patches in the next weeks.



Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Christian Lamprechter
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928