LLVM IR influence on compiler debugging

[Adam Wilson]

On Sat, 07 Jul 2012 16:38:27 -0700, Timon Gehr <timon.gehr at gmx.ch> wrote:

> On 07/08/2012 01:28 AM, Adam Wilson wrote:
>> On Sat, 07 Jul 2012 16:15:11 -0700, Walter Bright
>> <newshound2 at digitalmars.com> wrote:
>>
>>> On 7/7/2012 4:08 PM, Adam Wilson wrote:
>>>> On Sat, 07 Jul 2012 11:48:44 -0700, Walter Bright
>>>> <newshound2 at digitalmars.com>
>>>> wrote:
>>>>
>>>>> On 7/7/2012 8:38 AM, Alex Rønne Petersen wrote:
>>>>>> On a high-end 4-core x86, building LLVM and LDC can usually be
>>>>>> done in less than an hour, even when building them in optimized  
>>>>>> mode.
>>>>>
>>>>> Building dmd on my Windows box takes 26 seconds, optimized, using a
>>>>> single core.
>>>>
>>>> Build speed of the compiler itself is an utterly trivial matter, my
>>>> primary
>>>> concern is speed for the end-user. Even the build speed/memory usage
>>>> of my
>>>> projects is not a problem, I can always throw more money at hardware.
>>>> For
>>>> example, I am considering making the next round of developer box
>>>> updates to
>>>> Intel Xeon E1650's with 32GB RAM.
>>>>
>>>> Gentlemen, from a business prospective, compiler and/or project build
>>>> times are
>>>> the least of your problems. How well the code performs and most
>>>> importantly the
>>>> accuracy of the code generation is of key concern.
>>>
>>> Throwing more hardware at a problem isn't going to get you a 120x
>>> increase in speed.
>>
>> I wont argue that, but again, that's not a primary concern. :-)
>>
>>> While you're right that the customer cares not how long it takes to
>>> build the compiler, the speed is important for the edit-compile-debug
>>> loop of developing the compiler. For me, it matters quite a bit.
>>
>> I imagine that it does, and honestly, I am not terribly concerned if DMD
>> stays with it's current backend because once LLVM gets SEH, im gone. But
>> I do wonder if DMD will become increasingly irrelevant as backends like
>> GCC and LLVM advance. And I am particularly troubled by what seems like
>> a duplication of effort in the face of more widely tested backends...
>>
>
> The DMD backend is very fast in comparison to other backends.
>
> LLVM is unlikely to catch up in speed, because it is well architectured
> and more general.
>

Oh, I agree that it is, but as I've been saying, raw compiler speed is  
rarely an important factor outside of small circles of developers, if it  
was, businesses would have given up on C++ LONG ago. It's nice to have,  
but the business case for it is weak comparatively.

>> All that said, I understand the legal predicament. You can't do anything
>> about it and I'm not trying to convince you too. I just want to see more
>> promotion and support of the other options available.
>>
>


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