Steve,
I could not get it...
The thing I see is that gcc can omit 'y' from rtl generation but very
unlikely cause you assign a value to it before asm operator...
~d
On Friday 13 September 2002 20:52, Steve Underwood wrote:
> Dmitry wrote:
> >could you please be more specific?
> >Are they eliminated during code generatin phase?
> >Have you tried to make one of them as input?
> >
> >Only whole asm operator can be deleted by gcc. So, try to recombine
> > params.
>
> OK. Here is a specific example - a sqrt function from the 430 apps.
> book, turned into a C function. This version does not work. x and y get
> merged, and are no longer separate working variables inside the asm code.
>
> int32_t isqrt32(register int32_t h)
> {
> register int32_t x;
> register int32_t y;
> register int16_t i;
>
> x =
> y = 0;
> i = 32;
> __asm__ (
> "1: \n"
> " setc \n"
> " rlc %A0 \n"
> " rlc %B0 \n"
> " sub %A0,%A1 \n"
> " subc %B0,%B1 \n"
> " jhs 2f \n"
> " add %A0,%A1 \n"
> " addc %B0,%B1 \n"
> " sub #2,%A0 \n"
> "2: \n"
> " inc %A0 \n"
> " rla %A2 \n"
> " rlc %B2 \n"
> " rlc %A1 \n"
> " rlc %B1 \n"
> " rla %A2 \n"
> " rlc %B2 \n"
> " rlc %A1 \n"
> " rlc %B1 \n"
> " dec %3 \n"
> " jne 1b \n"
>
> : "+r"(x), "+r"(y)
> : "r"(h), "r"(i));
>
> return x;
> }
>
> The works. The values of x and y are now different as we enter the asm
> code, so GCC cannot coalesce them. It allocates two registers for x and
> another 2 for y. All is well, as setting the top bit of x happens to be
> harmless. It wastes code, though. It gets me around the immediate
> problem, but it obviously not the right way to do things.
>
> int32_t isqrt32(register int32_t h)
> {
> register int32_t x;
> register int32_t y;
> register int16_t i;
>
> x = 0x80000000;
> y = 0;
> i = 32;
> __asm__ (
> "1: \n"
> " setc \n"
> " rlc %A0 \n"
> " rlc %B0 \n"
> " sub %A0,%A1 \n"
> " subc %B0,%B1 \n"
> " jhs 2f \n"
> " add %A0,%A1 \n"
> " addc %B0,%B1 \n"
> " sub #2,%A0 \n"
> "2: \n"
> " inc %A0 \n"
> " rla %A2 \n"
> " rlc %B2 \n"
> " rlc %A1 \n"
> " rlc %B1 \n"
> " rla %A2 \n"
> " rlc %B2 \n"
> " rlc %A1 \n"
> " rlc %B1 \n"
> " dec %3 \n"
> " jne 1b \n"
>
> : "+r"(x), "+r"(y)
> : "r"(h), "r"(i));
>
> return x;
> }
>
>
> Regards,
> Steve
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
> Welcome to geek heaven.
> http://thinkgeek.com/sf
> _______________________________________________
> Mspgcc-users mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/mspgcc-users
--
*********************************************************************
("`-''-/").___..--''"`-._ (\ Dimmy the Wild UA1ACZ
`6_ 6 ) `-. ( ).`-.__.`) Enterprise Information Sys
(_Y_.)' ._ ) `._ `. ``-..-' Nevsky prospekt, 20 / 44
_..`--'_..-_/ /--'_.' ,' Saint Petersburg, Russia
(il),-'' (li),' ((!.-' +7 (812) 314-8860, 5585314
*********************************************************************
