DConf 2013 Day 3 Talk 4: LDC by David Nadlinger

[Kai Nacke]

On Monday, 17 June 2013 at 15:41:24 UTC, nazriel wrote:
> On Monday, 17 June 2013 at 13:47:20 UTC, bearophile wrote:
>> Andrei Alexandrescu:
>>
>>> http://www.reddit.com/r/programming/comments/1gie4b/dconf_2013_ldc_the_llvmbased_d_compiler_by_david/
>>
>> Slide 14:
>>
>> PFFT (SSE) seems slow on LDC2: if you can extract a small test
>> case LLVM devs will appreciate a lot a bug report (they fixed
>> many lacks of optimizations submitted by me). If you have a 
>> link
>> to the PFFT code them maybe I can do that myself.
>>
> I don't know what PFFT stands for (can't google it either, 
> funny results shows up) but if it related to vectorization then 
> maybe LDC has been slower because it was built against LLVM 3.3 
> while LLVM 3.4 brings more vector optimizations.
>
> Maybe all what has to be done, is rerunning benchmarks against 
> LDC + LLVM 3.4 ?

As far as I followed the LLVM commit list, the change is that the 
loop vectorizer is now enabled at -O2 (instead of -O3).
I don't know the options David has used but I assume something 
like "ldmd2 -O -inline -release". "-O" from ldmd2 maps to -O3 and 
therefore enables the loop vectorizer.

Regards
Kai

>>
>> Slide 25:
>>> Implicit invariants often hard to track down
>>
>> Then maybe it's a good idea to add such invariants to the dmd
>> front-end code, even before its port to D.
>>
>> Bye,
>> bearophile