LLVM IR influence on compiler debugging

[Timon Gehr]

On 07/08/2012 01:54 AM, Adam Wilson wrote:
> 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.
>

'raw compiler speed is rarely the most important factor' does not
necessarily imply 'raw compiler speed is rarely an important factor'.