[Bug c/57931] New: There are superfluous movw instructions in when using GCC-AVR (WinAVR) asm code.

[Bug c/57931] New: There are superfluous movw instructions in when using GCC-AVR (WinAVR) asm code.

[NickParker at Eaton dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57931

            Bug ID: 57931
           Summary: There are superfluous movw instructions in when using
                    GCC-AVR (WinAVR) asm code.
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: NickParker at Eaton dot com

Created attachment 30526
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30526&action=edit
C code and a listing

There are superfluous movw instructions in when using GCC-AVR (WinAVR) asm
code.

Might as well make some tighter code here!

[Bug target/57931] There are superfluous movw instructions in generated ASM code with GCC-AVR (WinAVR)

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57931

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Target|                            |avr
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |gjl at gcc dot gnu.org
         Resolution|---                         |WORKSFORME
              Build|avr                         |

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Newest "WinAVR" is avr-gcc 4.3.3 and thus is pretty much outdated.

I cannot confirm this with 4.8 where the generated code (after adding #include
<stdint> to the source) reads:

$ avr-gcc foo.c -mmcu=attiny85 -Os -std=gnu99 -S

median:
/* prologue: function */
/* frame size = 0 */
/* stack size = 0 */
.L__stack_usage = 0
    cp r24,r22
    cpc r25,r23
    brge .L2
    cp r24,r20
    cpc r25,r21
    brge .L3
    movw r24,r22
    rjmp .L10
.L2:
    cp r22,r20
    cpc r23,r21
    brge .L7
.L10:
    cp r20,r24
    cpc r21,r25
    brge .L3
    movw r24,r20
    ret
.L7:
    movw r24,r22
.L3:
    ret