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digitalmars.D - Does D (DMD/Win) use ES, FS & GS for anything?

reply "Me Here" <p9e883002 sneakemail.com> writes:
The subject pretty much says it all. I'd like to use one (or if possible, two)
of these registers in some assmbly code and want to know if I need to preserve
them or if D will just ignore them and leave them untouched between callbacks
into the assembler code?

Thanks, b.
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May 21 2008
next sibling parent Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:
Me Here wrote:

 The subject pretty much says it all. I'd like to use one (or if possible, two)
 of these registers in some assmbly code and want to know if I need to preserve
 them or if D will just ignore them and leave them untouched between callbacks
 into the assembler code?


ES is used by certain instructions the compiler generates (movs & 
friends, IIRC)
Windows exception handling uses FS.
I'm not sure about GS (nor FS on Linux, but you specified Windows so you 
don't care).
May 21 2008
prev sibling parent reply Walter Bright <newshound1 digitalmars.com> writes:
Me Here wrote:

 The subject pretty much says it all. I'd like to use one (or if possible, two)
 of these registers in some assmbly code and want to know if I need to preserve
 them or if D will just ignore them and leave them untouched between callbacks
 into the assembler code?


I recommend save/restoring them. GS, for example, is used in Linux for 
thread local storage. FS is used for exception handling. ES is used for 
string instructions.
May 21 2008
parent reply Sean Kelly <sean invisibleduck.org> writes:
== Quote from Walter Bright (newshound1 digitalmars.com)'s article

 Me Here wrote:

 The subject pretty much says it all. I'd like to use one (or if possible, two)
 of these registers in some assmbly code and want to know if I need to preserve
 them or if D will just ignore them and leave them untouched between callbacks
 into the assembler code?


 I recommend save/restoring them. GS, for example, is used in Linux for
 thread local storage. FS is used for exception handling. ES is used for
 string instructions.


In general, I think following the x86 C ABI is the best approach insofar as
register allocation and such is concerned.  I don't have the link handy, but
I believe it was published by Sun.  If I remember correctly, the only scratch
registers are EAX and EDX.


Sean
May 21 2008
parent reply "Me Here" <p9e883002 sneakemail.com> writes:
Sean Kelly wrote:


 In general, I think following the x86 C ABI is the best approach insofar as
 register allocation and such is concerned.  I don't have the link handy, but
 I believe it was published by Sun.


I don't suppose I could impose on you for a few more clues as to what you are
remembering?

Every search I've done looking for x86 ABI (with or without C and/or Sun) is
turning up the
AMD64 ABI...which doesn't seem to applicable to what I'm trying to do. 

(It may in the future if I ever try to code for 64-bit, but what I'm working on 
is so machine wordsize specific that everything will have to change anyway).

Thanks for any and all latent memory pointers you can provide :)

b.
--
May 21 2008
next sibling parent Walter Bright <newshound1 digitalmars.com> writes:
Me Here wrote:

 Thanks for any and all latent memory pointers you can provide :)


On windows and linux, you can modify EAX, ECX and EDX. The rest must be 
preserved.
May 21 2008
prev sibling parent reply Sean Kelly <sean invisibleduck.org> writes:
Me Here wrote:

 Sean Kelly wrote:
 

 In general, I think following the x86 C ABI is the best approach insofar as
 register allocation and such is concerned.  I don't have the link handy, but
 I believe it was published by Sun.


 
 I don't suppose I could impose on you for a few more clues as to what you are
 remembering?
 
 Every search I've done looking for x86 ABI (with or without C and/or Sun) is
 turning up the
 AMD64 ABI...which doesn't seem to applicable to what I'm trying to do. 
 
 (It may in the future if I ever try to code for 64-bit, but what I'm working
on 
 is so machine wordsize specific that everything will have to change anyway).
 
 Thanks for any and all latent memory pointers you can provide :)


I think this is the one I was referring to:

http://www.sco.com/developers/devspecs/abi386-4.pdf


Sean
May 25 2008
parent "Me Here" <p9e883002 sneakemail.com> writes:
Sean Kelly wrote:


 Me Here wrote:

 Sean Kelly wrote:
 

 In general, I think following the x86 C ABI is the best approach insofar
 as register allocation and such is concerned.  I don't have the link
 handy, but I believe it was published by Sun.







 Thanks for any and all latent memory pointers you can provide :)


 
 I think this is the one I was referring to:
 
 http://www.sco.com/developers/devspecs/abi386-4.pdf
 
 
 Sean


Many thanks. That is very useful.
b.
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May 26 2008