[Bug c++/13413] New: need "o" inline asm constraint

[Bug c++/13413] New: need "o" inline asm constraint

[melkov at comptek dot ru]

I think that having no "o" constraint is asm for i386 target is unfair, because 
in effect all the "m" values are actually offsetable.
For example, when I write:
movl 4+%5, %2
- I always get correct code.
The only problem here is that I get gas warning each time %5 happens to be a 
base register without an offset, i.e. something like (%ebx) turns the above 
line into
movl 4+(%ebx), %eax

If there was "o" constraing that behaves like "m" in most cases but prints zero 
in case of zero offset, some people like me would be happy.

What I want, once again:
%5 == (%ebx)
"m" prints (%ebx)
"o" prints 0(%ebx)
-> quite correct movl 4+0(%ebx), %eax in "o" case.

%5 == 12(%ebx)
both "m" and "o" print (%ebx)
-> still correct movl 4+12(%ebx), %eax code.

I hope that's easy to do. Thanks in advance :)

-- 
           Summary: need "o" inline asm constraint
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: melkov at comptek dot ru
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-freebsd-gnu
  GCC host triplet: i686-freebsd-gnu
GCC target triplet: i686-freebsd-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13413

[Bug inline-asm/13413] need "o" inline asm constraint

[bangerth at dealii dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |inline-asm


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13413

[Bug target/13413] need "o" inline asm constraint

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|inline-asm                  |target


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13413

[Bug target/13413] need "o" inline asm constraint

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-19 07:36 -------
So this is what you want:
int f(int *i){int t; asm("a %1":"=r"(t):"o"(*i)); return t;}
0(%eax) and not (%eax) which it currently is now, right?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-12-19 07:36:29
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13413

[Bug target/13413] need "o" inline asm constraint

[melkov at comptek dot ru]

------- Additional Comments From melkov at comptek dot ru  2003-12-19 21:35 -------
(In reply to comment #1)
> So this is what you want:
> int f(int *i){int t; asm("a %1":"=r"(t):"o"(*i)); return t;}
> 0(%eax) and not (%eax) which it currently is now, right?
Yes, that's right.

But that's not enough. Nowadays gcc doesn't like "o" at all, it says: "error: 
impossible constraint in `asm'".

/usr/local/egcs-3/bin/c++ -O -Wall mo.cpp
mo.cpp: In function `int main(int, char**)':
mo.cpp:3: error: impossible constraint in `asm'

==> mo.cpp <==
int main(int argc, char *[]) {
    long long A = argc;
    asm volatile(
        ""
        : "=o" (A)
        :
        : "cc"
    );
    return A;
}

With "m", it compiles fine. (note -O switch)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13413