🚀 go-pugleaf

In the following example, the powerpc version of gcc produces an
RS6000 opcode that isn't understood by the powerpc assembler.  The
example source file is abstracted from cluster_read() in vfs_cluster.c
in the BSD/OS kernel...  For what it's worth, I'm still cross-compiling
from i386 to powerpc, although I don't think that matters here.

% cc -v -O2 -c max.c
gcc version 2.7.1
 /u/donn/ppclibexec/cpp -lang-c -v -iprefix /u/donn/ppclibexec/powerpc/2.7.1/ -undef -D__GNUC__=2 -D__GNUC_MINOR__=7 -D__bsdi__ -Dbsdi -Dunix -D__powerpc__ -D__bsdi__ -D__bsdi__ -D__unix__ -D__powerpc__ -D__bsdi -D__unix -Asystem(unix) -Asystem(bsd) -Acpu(powerpc) -Amachine(powerpc) -D__CHAR_UNSIGNED__ -D__OPTIMIZE__ -D_CALL_SYSV -D_BIG_ENDIAN -Amachine(bigendian) -D_ARCH_PPC max.c /tmp/cc021147.i
GNU CPP version 2.7.1 (PowerPC BSD/OS)
#include "..." search starts here:
#include <...> search starts here:
 /u/donn/ppclibexec/powerpc/2.7.1/local/include
 /u/donn/ppclibexec/powerpc/2.7.1/include
 /u/donn/ppclibexec/powerpc/2.7.1/include
 /u/donn/ppclibexec/powerpc/2.7.1/include
 /usr/local/include
 /usr/include
 /usr/include
 /usr/include
End of search list.
 /u/donn/ppclibexec/cc1 /tmp/cc021147.i -quiet -dumpbase max.c -O2 -version -o /tmp/cc021147.s
GNU C version 2.7.2 (PowerPC BSD/OS) compiled by GNU C version 2.7.1.
 as -u -mppc -V -Qy -o max.o /tmp/cc021147.s
GNU assembler version 2.6 (bsd/os), using BFD version 2.6
/tmp/cc021147.s: Assembler messages:
/tmp/cc021147.s:23: Error: Unrecognized opcode: `ai'
% cat max.c
struct v { unsigned int v_maxra, v_ralen; };

void
maxbug(struct v *vp, unsigned int ioblkno)
{

                if (ioblkno <= vp->v_maxra)
                        vp->v_ralen = ({ unsigned int _a = ( vp->v_ralen >> 1 ),
 _b = (  1 ); _a > _b ? _a : _b; }) ;
}
% 

The following patch seems to fix it, or at least makes 2.7.2 compile
the example into legal powerpc assembly:

Index: rs6000.md
===================================================================
RCS file: /master/usr.bin/gcc2/config/rs6000/rs6000.md,v
retrieving revision 2.3
diff -c -r2.3 rs6000.md
*** 2.3	1995/12/06 09:31:49
--- rs6000.md	1995/12/08 00:03:41
***************
*** 6909,6915 ****
    ""
    "@
     {sf|subfc} %0,%2,%1\;{sfe|subfe} %0,%0,%0\;nand %0,%0,%0
!    {sfi|subfic} %0,%1,-1\;a%I2 %0,%0,%2\;{sfe|subfe} %0,%0,%0"
    [(set_attr "length" "12")])
  
  (define_insn ""
--- 6909,6915 ----
    ""
    "@
     {sf|subfc} %0,%2,%1\;{sfe|subfe} %0,%0,%0\;nand %0,%0,%0
!    {sfi|subfic} %0,%1,-1\;{a%I2|add%I2} %0,%0,%2\;{sfe|subfe} %0,%0,%0"
    [(set_attr "length" "12")])
  
  (define_insn ""

Donn Seeley / BSDI Engineering