AST files instead of DI interface files for faster compilation and easier distribution

[Iain Buclaw]

On 13 June 2012 09:07, Don Clugston <dac at nospam.com> wrote:
> On 12/06/12 18:46, Walter Bright wrote:
>>
>> On 6/12/2012 2:07 AM, timotheecour wrote:
>>>
>>> There's a current pull request to improve di file generation
>>> (https://github.com/D-Programming-Language/dmd/pull/945); I'd like to
>>> suggest
>>> further ideas.
>>> As far as I understand, di interface files try to achieve these
>>> conflicting goals:
>>>
>>> 1) speed up compilation by avoiding having to reparse large files over
>>> and over.
>>> 2) hide implementation details for proprietary reasons
>>> 3) still maintain source code in some form to allow inlining and CTFE
>>> 4) be human readable
>>
>>
>> (4) was not a goal.
>>
>> A .di file could very well be a binary file, but making it look like D
>> source enabled them to be loaded with no additional implementation work
>> in the compiler.
>
>
> I don't understand (1) actually.
>
> For two reasons:
> (a) Is lexing + parsing really a significant part of the compilation time?
> Has anyone done some solid profiling?
>

Lexing and Parsing are miniscule tasks in comparison to the three
semantic runs done on the code.

I added speed counters into the glue code of GDC some time ago.
http://iainbuclaw.wordpress.com/2010/09/18/implementing-speed-counters-in-gdc/

And here is the relavent report to go with it.
http://iainbuclaw.files.wordpress.com/2010/09/d2-time-report2.pdf


Example: std/xml.d
Module::parse : 0.01 ( 0%)
Module::semantic : 0.50 ( 9%)
Module::semantic2 : 0.02 ( 0%)
Module::semantic3 : 0.04 ( 1%)
Module::genobjfile : 0.10 ( 2%)

For the entire time it took to compile the one file (5.22 seconds) -
it spent almost 10% of it's time running the first semantic analysis.


But that was the D2 frontend / phobos as of September 2010.  I should
re-run a report on updated times and draw some comparisons. :~)


Regards
-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';