LLVM IR influence on compiler debugging

[Adam Wilson]

On Sat, 07 Jul 2012 21:05:12 -0700, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

> On 7/7/12 11:26 PM, Adam Wilson wrote:
>> On Sat, 07 Jul 2012 19:33:22 -0700, Andrei Alexandrescu
>> <SeeWebsiteForEmail at erdani.org> wrote:
>>
>>> On 7/7/12 8:29 PM, Adam Wilson wrote:
>>>> Sure they complain, but they would complain harder if the generated  
>>>> code
>>>> was sub-optimal or had bugs in it. And I imagine that multiple hour
>>>> build times are more the exception than rule even in C++, my
>>>> understanding is that all 50mloc of Windows can compile overnight  
>>>> using
>>>> distributed compiling. Essentially, my argument is that for business
>>>> compilation time is something that can be attacked with money, where
>>>> code generation and perf bugs are not.
>>>
>>> I'm sorry, but I think you got that precisely backwards.
>>>
>>> Andrei
>>
>> Why is that?
>
> Compilation is a huge bottleneck for any major C++ code base, and adding  
> hardware (distributing compilation etc) is survival, but definitely  
> doesn't scale to make the problem negligible.
>
> In contrast, programmers have considerable control about generating fast  
> code.
>
>
> Andrei
>
>

So work around backend bugs and slowness? I could see that, but the most  
widely used C++ compilers are based on GCC and LLVM and those have very  
few backend problems to begin with. I still see pretty heinous backend  
problems crop up in the bug reports for DMD.

As to compile speed, is LDC really *THAT* much slower than DMD so as to  
cause C++ style speed issues? I thought one of the whole points of D is  
that it doesn't need the epic numbers of passes and preprocessor that C++  
does precisely because that's what slows down C++ so much...

-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/