[Dwarf-Discuss] DwarfExtensions

[David Anderson]

On 07/26/2012 03:11 AM, Mark Wielaard wrote:
> Hi,
>
> For the elfutils project (https://fedorahosted.org/elfutils/), which
> includes libdw a DWARF consumer library used by programs like perf,
> systemtap and the dwarves tools, I wrote up a wiki page with all the
> DWARF extensions known to the library:
>
> https://fedorahosted.org/elfutils/wiki/DwarfExtensions
>

Some comments.

Some of the DW_AT_MIPS extensions were invented in the mid 1990's at SGI but 

were never emitted.  No SGI compiler emitted them that I am aware of
(I was in the compiler group 1988-2006 and responsible for libdwarf and 
for SGI debuggers
among other things).   These were given the designation MIPS (instead of 
SGI)
because we thought that was just a better thing to do.


DW_TAG_MIPS_loop
DW_AT_MIPS_loop_begin
DW_AT_MIPS_tail_loop_begin
DW_AT_MIPS_epilog_begin
DW_AT_MIPS_loop_unroll_factor
DW_AT_MIPS_software_pipeline_depth

are in the class of attributes that were never implemented at SGI/MIPS. 
So I doubt if anyone
ever emitted them.  The implied compiler optimizations were done at SGI 
in-period, but no
DWARF was emitted describing the optimizations.

The mips_extensions pdf (written by me at SGI
in-period and still distributed with libdwarf and dwarfdump)  which 
explains
what some of the original MIPS
extensions (only a couple of which were widely used)
meant. (I emailed Mark the pdf in separate email).

Corrections are welcome.

David Anderson

-- 
I told the doctor I broke my leg in two places. He told me to quit going to those places. -- Henny Youngman