[Bug target/33050] [avr] unnessary register save

["wvangulik at xs4all dot nl" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from wvangulik at xs4all dot nl  2007-08-24 19:36 -------
(In reply to comment #2)
> 4.3.0 20070817 snapshot generates this for the testcase:
> 

<snip>

Well at least the extra clr r25 is gone...


I just tried some simpler code:

extern unsigned char foo();
unsigned char test(unsigned char input) {
  return input += foo();
}

The result is:
/* prologue: frame size=0 */
        push r17
/* prologue end (size=1) */
        mov r17,r24
        call foo
        add r17,r24            <<Could do "add r24,r17"
        mov r24,r17            <<This could then be gone
        clr r25                <<This is maybe gone in 4.3.0??
/* epilogue: frame size=0 */
        pop r17
        ret
/* epilogue end (size=2) */

Here the add is also done non-optimal. So maybe solving this prevents the extra
register save?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33050