[Bug c/33674] New: Nonexistent i386 register name `%SIL' used

["richardpku at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

GCC tries to use a register `%SIL' in my test on an i386 machine. However, the
lowest 8 bits of ESI can be directly accessed only in x86-64, but not i386. I
also observe in other tests the use of another two bad register names `%DIL'
and `%BPL'.

The following code can reproduce the bug:

static inline char contain (const char *ptr, int len, char c)
{
        char    r;
        int     od,oc;
        asm volatile (
                "cld\n\t"
                "repnz scasb\n\t"
                "sete %0"
                :"=r"(r),"=D"(od),"=c"(oc)
                :"c"(len),"a"(c),"D"(ptr)
        );
        return r;
}

__attribute__((regparm(3)))
int     test(int a, int b, int c, int d, const char *buf, int len, int ch)
{
        d += a * b;
        if (contain (buf, len, ch))
                a++;
        return a+b+c+d;
}


The command line and the error message:
$ gcc -save-temps -O1 -c test.c -Wall -Wextra
test.s: Assembler messages:
test.s:21: Error: bad register name `%sil'

I checked the assembly output and found that GCC had allocated `%SIL' for `r'
in function `contain'.

The following is my GCC version info:
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2
--enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr
--enable-targets=all --enable-checking=release --build=i486-linux-gnu
--host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.2.1 (Debian 4.2.1-6)


-- 
           Summary: Nonexistent i386 register name `%SIL' used
           Product: gcc
           Version: 4.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: richardpku at gmail dot com
 GCC build triplet: i486-linux-gnu
  GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33674