[m-rev.] for review: add ll_debug GC grade

[Ian MacLarty]

On Wed, Dec 7, 2011 at 11:04 AM, Julien Fischer
<juliensf at csse.unimelb.edu.au> wrote:
>
> On Wed, 7 Dec 2011, Peter Ross wrote:
>
>> On 6 December 2011 20:29, Ian MacLarty <maclarty at csse.unimelb.edu.au>
>> wrote:
>>>
>>> For review by Julien.
>>>
>>> Branches: main, 11.07
>>>
>>> Add a new GC grade for the .ll_debug Mercury grade.
>>>
>>> Previously the .ll_debug grade used the usual "gc" GC grade.  This was a
>>> problem, because it meant that installing a .ll_debug grade would
>>> overwrite the
>>> libgc library with the unoptimised .ll_debug version, resulting in a
>>> severe
>>> performance loss for applications even if they weren't built in the
>>> .ll_debug
>>> grade.
>>>
>>> compiler/compile_target_code.m:
>>>    Link against the ll_debug GC library if low-level debugging
>>>    is enabled.
>>>
>>> scripts/ml.in:
>>>    Use the new ll_debug GC grade for the .ll_debug Mercury
>>>    grades.
>>>
>> Maybe the ll_debug grade should imply the gcd grade?  Rather than
>> installing a new version of the gc library.
>
>
> I disagree.  I use the ll_debug grade quite a bit for debugging programs
> written in the hlc grade that make heavy use of the C foreign code.
> I have nver required the gcd grades for this; outside of debugging
> interactions between the collector and the rest of the system I think
> they are of too limited use.

But would it hurt to use the .gcd version of boehm in ll_debug grades?
 In ll_debug grades C optimizations are already turned off, so what
difference will also disabling NO_DEBUGGING in boehm make?

It just seems a bit confusing to have two debug versions of the GC library.

What about the following solution:

- Make the .gcd Mercury grade component also imply -g -O0 when building boehm.
- Make the .ll_debug Mercury grade component turn off -DNO_DEBUGGING in boehm.
(So boehm is built the same way if we're using either .ll_debug or
.gcd mercury grade components).
- Make the .ll_debug Mercury grade component imply the gc_debug GC
grade component (i.e. make it use the .gcd version of boehm).

Ian.

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