[avr-gcc-list] Prologue keeps registers which will not be restored ?

[Dmitry K.]

Good evening!

Prologue keeps registers which will not be restored ?
By the way, in the received code an appreciable error.

Programm:

        unsigned char f(void);

        void foo (void)
        {
           while ( ((f() ^ 1) & 1) == 0 ) ;
        }

Options:

        avr-gcc -W -Wall -S -O2 prol-155.c

Result:

        .file   "prol-155.c"
        .arch avr2
__SREG__ = 0x3f
__SP_H__ = 0x3e
__SP_L__ = 0x3d
__tmp_reg__ = 0
__zero_reg__ = 1
        .global __do_copy_data
        .global __do_clear_bss
        .text
.global foo
        .type   foo, @function
foo:
/* prologue: frame size=0 */
        push r28
/* prologue end (size=1) */
.L2:
        rcall f
        rjmp .L2
/* epilogue: frame size=0 */
/* epilogue: noreturn */
/* epilogue end (size=0) */
/* function foo size 3 (2) */
        .size   foo, .-foo
/* File "prol-155.c": code    3 = 0x0003 (   2), prologues   1, epilogues   0 
*/