[Bug inline-asm/37895] AVR inline assembly clobbers input value

["avr at gjlay dot de" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37895

Georg-Johann Lay <avr at gjlay dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eric.weddington at atmel
                   |                            |dot com

--- Comment #2 from Georg-Johann Lay <avr at gjlay dot de> 2011-03-12 13:01:13 UTC ---
I can not confirm the problems for WinAVR-20071221 (gcc 4.2.2)

With the following function

int32_t test_mul (void)
{
    int32_t res = mul_16_8(0x1234, 0x56);
    return res;
}

Both the generated code and the result of the computation (400760 in that
specific case) are as expected.

Presumably there is an error in your code outside the snippet (which we aren't
allowed to see), maybe some signed/undigned clashes, promotion problems,
overflows, etc.

The code compiles with 
  -S -Os -mmcu=atmega88 -fverbose-asm
to

<asm>
test_mul:
/* prologue: frame size=0 */
/* prologue end (size=0) */
    ldi r24,lo8(4660)     ;  tmp43,
    ldi r25,hi8(4660)     ;  tmp43,
    ldi r18,lo8(86)     ;  tmp44,
    movw r20,r24     ; , tmp43
/* #APP */
    clr r24;     ;  res
    clr r25;     ;  res
    mul r20, r18;     ; , tmp44
    movw r22, r0;     ;  res
    mul r21, r18;     ; , tmp44
    add r23, r0;     ;  res
    adc r24, r1;     ;  res
    clr __zero_reg__

/* #NOAPP */
/* epilogue: frame size=0 */
    ret
</asm>
which is correct. gcc respects the early-clobber, i.e. the output operand
(r22-r25) does not overlap an input operand (r20-r21 and r18).

IMO this bug is invalid and can be closed.

Johann