Re: [fpc-devel] Vectorization

[J. Gareth Moreton]

The idea I had currently (this is without 
looking at any previous theory) was to use 
a kind of sliding window, similar to how 
ZIP and other LZ77-based algorithms work 
when compressing repeating strings, to 
look backwards in the current block for a 
matching command and then scan forward. If 
the scan gets up to the instruction right 
before the starting point, then it's 
potential for vectorisable code. Using the 
previous example:

movss 16(%rsp),%xmm0
addss 32(%rsp),%xmm0
movss %xmm0,(%rax)
movss 20(%rsp),%xmm0
addss 36(%rsp),%xmm0
movss %xmm0,4(%rax)

Starting at the 4th command, it looks back 
to find a match in the 1st command, albeit 
with Ann address that differs only by 4. 
As it scans forward, it finds similar 
matches in subsequent commands, and 
eventually realises the entire block could 
potentially be vectorised. If it 
continues, it finds the code fragment 
repeats 4 times and can be vectorised with 
little difficulty. Being only SSE commands 
helps too.

Kit

P.S. I did look at the loop unrolling 
code, but it almost never triggers due to 
the small instruction cache that's 
assumed. For x86-64, is it safe to assume 
a cache length of 60 instead of 30, since 
almost all modern Intel and AMD processors 
have 56+ elements in their queues.

On Sun 10/12/17 13:50 , "Florian Klämpfl" 
flor...@freepascal.org sent:
> Am 10.12.2017 um 02:29 schrieb J. Gareth 
Moreton:
> 
> > Hi everyone,
> 
> > 
> 
> > Since I'm masochistic in my desire to 
understand
> and improve the Free Pascal Compiler, I 
would like to add 
> > some vectorisation support in its 
optimisation
> cycle, since that is one thing that many 
other compilers 
> > attempt to do these days.  But before 
I begin,
> does FPC support any kind of 
vectorisation already?  If it 
> > does I haven't been able to find it 
yet, and I
> don't want to end up reinventing the 
wheel.
> 
> 
> I started once to work on this, but 
never merged it into fpc trunk, it
> might be even only in my
> local git check out, I can look for it.
> 
> 
> 
> > 
> 
> > I'm sure it's a mammoth task, but I 
would like
> to start somewhere with it - however, 
are there any design 
> > plans that I should be adhering to so 
I don't
> end up designing something that is 
disliked?
> > 
> 
> 
> 
> Well, basically it means that another 
pass (like e.g. unroll_loop in
> optloop.pas) of the tree must
> be added which generated operations as 
they can be encoded by -Sv. To do
> this efficiently, probably
> some previous simplification of the tree 
is needed. But this is something
> for later.
> 
__
_
> 
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de...@lists.freepascal.org
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bin/mailman/listinfo/fpc-devel
> 
> 
> 
> 

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Re: [fpc-devel] Compiler error for target AVR - r37660

[Florian Klämpfl]

Am 04.12.2017 um 20:19 schrieb Christo:
>>
>> I guess I'm missing something?
> 
> OK, missed a comment marker in the config file which is now fixed. Now I get 
> the origninal error
> - Cannot find system type "variant"

It should be fixed meanwhile.

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Re: [fpc-devel] Quickly recompiling fpc

[Ondrej Pokorny]

On 09.12.2017 16:57, Sven Barth via fpc-devel wrote:
Am 09.12.2017 14:57 schrieb "Benito van der Zander" 
>:


Hi,

how do you recompile fpc after making a small change in the
compiler, like enabling the debugmsg define in x86/aoptx86.pas?

make buildbase says nothing was changed, and make clean; make
buildbase recompiles not just the compiler, but also the rtl,
which is a waste of time.


Build it in the Lazarus IDE using the corresponding project for your 
platform (this will result in a compiler//pp(.exe) binary).
Other than that "make cycle" inside the compiler directory *is* the 
recommended way to rebuild the compiler even if it rebuilds both the 
compiler and the RTL multiple times.


I only extend: don't forget you can use the "Run Parameters" dialog to 
debug the modified compiler with a sample PAS program.


Ondrej
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Re: [fpc-devel] Quickly recompiling fpc

[Florian Klämpfl]

Am 09.12.2017 um 14:49 schrieb Benito van der Zander:
> Hi,
> 
> how do you recompile fpc after making a small change in the compiler, like 
> enabling the debugmsg
> define in x86/aoptx86.pas?
> 
> make buildbase says nothing was changed, and make clean; make buildbase 
> recompiles not just the
> compiler, but also the rtl, which is a waste of time.

For compiler development, I do not use the makefiles, I just use lazarus and 
work with the
executables fpc builds when invoked from lazarus. Alternatively, you can do 
something like
cd fpc/compiler
rm ppc386
make
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Re: [fpc-devel] Vectorization

[Florian Klämpfl]

Am 10.12.2017 um 02:29 schrieb J. Gareth Moreton:
> Hi everyone,
> 
> Since I'm masochistic in my desire to understand and improve the Free Pascal 
> Compiler, I would like to add 
> some vectorisation support in its optimisation cycle, since that is one thing 
> that many other compilers 
> attempt to do these days.  But before I begin, does FPC support any kind of 
> vectorisation already?  If it 
> does I haven't been able to find it yet, and I don't want to end up 
> reinventing the wheel.

I started once to work on this, but never merged it into fpc trunk, it might be 
even only in my
local git check out, I can look for it.

> 
> I'm sure it's a mammoth task, but I would like to start somewhere with it - 
> however, are there any design 
> plans that I should be adhering to so I don't end up designing something that 
> is disliked?
> 

Well, basically it means that another pass (like e.g. unroll_loop in 
optloop.pas) of the tree must
be added which generated operations as they can be encoded by -Sv. To do this 
efficiently, probably
some previous simplification of the tree is needed. But this is something for 
later.
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Re: [fpc-devel] Vectorization

[Florian Klämpfl]

Am 10.12.2017 um 14:03 schrieb Marco van de Voort:
> In our previous episode, J. Gareth Moreton said:
>> Since I'm masochistic in my desire to understand and improve the Free Pascal 
>> Compiler, I would like to add 
>> some vectorisation support in its optimisation cycle, since that is one 
>> thing that many other compilers 
>> attempt to do these days.  But before I begin, does FPC support any kind of 
>> vectorisation already?  
> 
> Yes, -Sv, but it is buggy.

Well, -Sv means that operations on vectors are supported but it does not mean 
that FPC detects
vectorizable operations by itself.


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Re: [fpc-devel] Vectorization

[Marco van de Voort]

In our previous episode, J. Gareth Moreton said:
> Since I'm masochistic in my desire to understand and improve the Free Pascal 
> Compiler, I would like to add 
> some vectorisation support in its optimisation cycle, since that is one thing 
> that many other compilers 
> attempt to do these days.  But before I begin, does FPC support any kind of 
> vectorisation already?  

Yes, -Sv, but it is buggy.
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