c inline assembly

c inline assembly

[ratheesh kannoth]

I am using gcc on a 32bit  intel machine.  i have defined an inline function.


This function is inline .  what all registers needs to pushed and
poped in the inline assembly so that the functions wont
disturb the registers in  the function ( in which it is C inlined  ).


inline unsigned long hello(unsigned long a)

{
 int b;
 asm ("movl %1, %%eax;
      " movl %1, %%ebx;
       "movl  %1, %%ecx;
       "movl  %1, %%esi;
       "movl  %1, %%edi;

       "movl %%eax, %0;"
       :"=r"(b)        /* output */
       :"r"(a)         /* input */
 );
}
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Re: c inline assembly

[Ian Lance Taylor]

ratheesh kannoth <ratheesh.ksz@gmail.com> writes:

> This function is inline .  what all registers needs to pushed and
> poped in the inline assembly so that the functions wont
> disturb the registers in  the function ( in which it is C inlined  ).

Your asm statement should list the registers that it clobbers.

One i386 you normally can not clobber %ebp.  When compiling with
-fpic/-fPIC you normally can not clobber %ebx.

Ian

Re: c inline assembly

[Gedare Bloom]

On Sat, Feb 18, 2012 at 1:01 AM, ratheesh kannoth
<ratheesh.ksz@gmail.com> wrote:
> I am using gcc on a 32bit  intel machine.  i have defined an inline function.
>
>
> This function is inline .  what all registers needs to pushed and
> poped in the inline assembly so that the functions wont
> disturb the registers in  the function ( in which it is C inlined  ).
>
Use the clobber list:
http://ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html#ss5.3

>
> inline unsigned long hello(unsigned long a)
>
> {
>  int b;
>  asm ("movl %1, %%eax;
>      " movl %1, %%ebx;
>       "movl  %1, %%ecx;
>       "movl  %1, %%esi;
>       "movl  %1, %%edi;
>
>       "movl %%eax, %0;"
>       :"=r"(b)        /* output */
>       :"r"(a)         /* input */
         : "eax","ecx","esi","edi" /* clobber */
>  );
> }
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Re: c inline assembly

[Vladimir Murzin]

Hi!

What is you question or request? ;-)

------Original Message------
From: ratheesh kannoth
Sender: linux-c-programming-owner@vger.kernel.org
To: linux-c-programming@vger.kernel.org
To: gcc-help@gcc.gnu.org
Subject: c inline assembly
Sent: 18 Feb 2012 10:01

I am using gcc on a 32bit  intel machine.  i have defined an inline function.


This function is inline .  what all registers needs to pushed and
poped in the inline assembly so that the functions wont
disturb the registers in  the function ( in which it is C inlined  ).


inline unsigned long hello(unsigned long a)

{
 int b;
 asm ("movl %1, %%eax;
      " movl %1, %%ebx;
       "movl  %1, %%ecx;
       "movl  %1, %%esi;
       "movl  %1, %%edi;

       "movl %%eax, %0;"
       :"=r"(b)        /* output */
       :"r"(a)         /* input */
 );
}
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Best wishes,
Vladimir Murzin