Help needed on inline assembly

[Don Clugston]

Hendrik Renken wrote:
> Jarrett Billingsley wrote:
>> "Hendrik Renken" <funsheep at -[no-spam]-gmx.net> wrote in message 
>> news:fnqet1$1on0$1 at digitalmars.com...
>>
>>> Doesnt seem to work for me (using DMD 1.026 on linux). Or the aligment
>>> is in 1.026 broken again...
>>
>> Ah, it's probably because of Linux.  That code works on Windows.  I 
>> forgot that DMD uses ELF on Linux like GDC.  DMD maybe can't control 
>> the alignment of the data there.
>>
>> Either that, or it's a genuine bug.  :\ 
> 
> i did some more testing, it seems that dynamically allocated data is 
> aligned. for that i can use movaps. however statically allocated data is 
> not aligned. but we can allocate 1 to 3 ints/floats/etc before the data, 
> until it is aligned ;)

That's what I found on Windows, and persuaded Walter to fix it. I didn't realise 
it wasn't working on Linux yet.
I hope that eventually we'll get stack data properly aligned; if it gets into 
the D ABI, then we only have to worry about callbacks from C -- ie, only 
extern() functions would need to align the stack.

> thanks for the help, got it working - and a speedup factor of 240! yeah. 
> from 480 millisec down to 2 millisec with sse instructions.
> 
> that rocks!

Oh yeah!
DMD's floating point code generation is very basic; it does almost no 
optimisation; and it's excellent support for inline asm makes asm particularly 
attractive.
But a factor of 240 is pretty extreme.