Hi,

while I wrote a module using inline assembler, I saw that DMC assumes that EBX will never change. Are there any other registers that must not be altered while compiling with -mn?

Best regards,
Mark Junker

Mark Junker wrote:

> Hi,
> 
> while I wrote a module using inline assembler, I saw that DMC assumes that  EBX will never change. Are there any other registers that must not be altered  while compiling with -mn?
> 
> Best regards,
> Mark Junker
> 
> 


16 bit models:

must preserve si,di,bp,sp,ss,cs,ds
direction flag (df) must stay forward

32 bit models:

must preserve ebx,esi,edi,ebp,esp,ss,fs,gs,cs,ds
direction flag (df) must stay forward
direction flag (df) must stay forward


roland

roland schrieb...
> 32 bit models:
> 
> must preserve ebx,esi,edi,ebp,esp,ss,fs,gs,cs,ds
> direction flag (df) must stay forward

Are fs dn gs used at all by the compiler (or RTL)?

- Heinz

Heinz Saathoff wrote:

> roland schrieb...
> 
>>32 bit models:
>>
>>must preserve ebx,esi,edi,ebp,esp,ss,fs,gs,cs,ds
>>direction flag (df) must stay forward
>>
> 
> Are fs dn gs used at all by the compiler (or RTL)?
> 
> - Heinz
> 


That is on my Symantec old docs. ( yes paper doc ! )
Never seen fs dn gs used when i disassembled.
May be Walter kept them at harm lenght just in case ..

by

roland

roland schrieb...
> Never seen fs dn gs used when i disassembled.
> May be Walter kept them at harm lenght just in case ..

That's what I also discovered. But I am not sure about the RTL where some support functions are written in assembler.

- Heinz

"Heinz Saathoff" <hsaat@bre.ipnet.de> wrote in message news:MPG.195a519c170ac08c9896c5@news.digitalmars.com...
> roland schrieb...
> > 32 bit models:
> >
> > must preserve ebx,esi,edi,ebp,esp,ss,fs,gs,cs,ds
> > direction flag (df) must stay forward
>
> Are fs dn gs used at all by the compiler (or RTL)?

FS is used by the Win32 operating system for thread-specific data, and is generated by the compiler for SEH stack frames. DS, of course, points to the data segment. I don't know what GS is used for.

Walter schrieb...
> FS is used by the Win32 operating system for thread-specific data, and is generated by the compiler for SEH stack frames.

What is a SEH stack frame? Has it to do with exception handlers (EH)?

- Heinz

"Heinz Saathoff" <hsaat@bre.ipnet.de> wrote in message news:MPG.195ccc6abe340d149896c7@news.digitalmars.com...
> Walter schrieb...
> > FS is used by the Win32 operating system for thread-specific data, and
is
> > generated by the compiler for SEH stack frames.
> What is a SEH stack frame?

Structured Exception Handling.

> Has it to do with exception handlers (EH)?

Yup. Compile some code with exceptions enabled, put some classes with destructors on the stack, and OBJ2ASM it.