[Bug optimization/11181] New: [avr-gcc] Optimization of "uchar/xor/and/single_bit" produced wrong code.

[dmixm@marine.febras.ru]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11181

           Summary: [avr-gcc] Optimization of "uchar/xor/and/single_bit"
                    produced wrong code.
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dmixm@marine.febras.ru
                CC: gcc-bugs@gcc.gnu.org
GCC target triplet: avr-unknown-none

Optimization of next program produced infinite loop: 
 
	unsigned char f(void); 
 
	void foo(void) 
	{ 
	    while ( ((f() ^ 1) & 1) == 0 ) ; 
	} 
 
Result is (avr-gcc -W -Wall -O1 -S xor.c): 
 
        .file   "xor.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 "xor.c": code    3 = 0x0003 (   2), prologues   1, epilogues   0 */