[Bug inline-asm/36558] New: "V" inline asm constraint not working on sparc64

["jakub at jermar dot eu" <gcc-bugzilla at gcc dot gnu dot org>]

The following program:

---&<---
static volatile long last;

main()
{
        long a, b;

        a = last;
        b = a + 1;
        asm volatile ("casx %0, %2, %1\n" : "+V" (last), "+r" (b) :"r" (a));
}
--->&---

will not compile.  The error message printed is:

jermar@phantom:~/x$ /usr/local/sparc64/bin/sparc64-linux-gnu-gcc -c test.c
test.c: In function 'main':
test.c:9: error: inconsistent operand constraints in an 'asm'

Even though the use of the "m" constraint will fix this testcase, "m" cannot be
used in general, because it allows the operand to be offsetable.  The casx
instruction will not tolerate an offset. According to gcc info page, "V" should
be just like "m", but not offsetable. Wonder why "V" does not work when "m"
does in this case.

Moreover, there are more or less ugly workarounds for this, but this has been
bugging me for some time and I think it should be fixed.

The gcc has been configured using:
configure --target=sparc64-linux-gnu --prefix=/usr/local/sparc64
--program-prefix=sparc64-linux-gnu- --with-gnu-as --with-gnu-ld --disable-nls
--disable-threads --enable-languages=c,objc,c++,obj-c++ --disable-multilib
--disable-libgcj --without-headers --disable-shared

Thanks,
Jakub


-- 
           Summary: "V" inline asm constraint not working on sparc64
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: inline-asm
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at jermar dot eu
 GCC build triplet: 4.3.1
  GCC host triplet: i486-linux-gnu
GCC target triplet: sparc64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36558