[Dri-devel] Re: Inline assembly question

[Mike A. H. <mh...@re...>]

On Sat, 31 Mar 2001, Greg Hughes wrote:

>Inline assembly experts,
>
>I've been palying with RedHat 7.1 Beta.  This ships with gcc 2.96.77,
>which is much better than the 2.96 bundled with RedHat 7.0.  This
>compiler can build the xc tree from the trunk, but it chokes trying to
>build the mesa-3-5-branch.  It doesn't like the COPY_DWORDS macro in the
>r128, radeon, and i810 directories.
>
>
>#define COPY_DWORDS( j, vb, vertsize, v )       \
>   __asm__ __volatile__( "rep ; movsl"          \
>                         : "=%c" (j), "=D" (vb) \
>                         : "0" (vertsize),      \
>                           "D" ((long)vb),      \
>                           "S" ((long)v)        \
>                         : "esi" )
>
>The error is:
>
>  Can't find a register in class `SIREG' while reloading `asm'.
>
>My question:  Is this a compiler defect, or is the compiler just being
>more strict?

I asked Jakub Jelinek about this and here is his response to the
question for you:

-----------------------------------------------------------------
This is wrong. Either is "S" used in input (or output or both
lists), or it is a clobber, never both. The above pattern
requests that v is to be passed in one-register class containing
%esi (SIREG) but compiler is not allowed to use %esi for that.

Doing something like:

#define COPY_DWORDS( j, vb, vertsize, v )       \
  do {                                            \
    unsigned int __x;                             \
    __asm__ __volatile__( "rep ; movsl"           \
                           : "=%c" (j), "=D" (vb),\
                             "=S" (__x)           \
                           : "0" (vertsize),      \
                             "1" ((long)vb),      \
                             "2" ((long)v));      \
  } while (0)

should fix it.

        Jakub
----------------------------------------------------------------

Hope this helps.

Take care!
TTYL



-- 
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