The following listing shows that the ~ operation is expanded to a short when
used in a conditional expression.
Attached is code with the problem, and the workaround.
----
unsigned char g()
{
return 0x5a;
}
void p(unsigned char c)
{
volatile unsigned char tmp;
tmp = c;
}
int main(int argc, char * argv[])
{
unsigned char XOR = 0xa5;
unsigned char tmp = 0;
if (g() == ~XOR)
p(tmp);
tmp = ~XOR;
if (g() == tmp)
p(tmp);
return 0;
}
----
if (g() == ~XOR)
ea: 0e 94 52 00 call 0xa4 ; 0xa4 <g>
ee: 28 2f mov r18, r24
f0: 30 e0 ldi r19, 0x00 ; 0
f2: 8a 81 ldd r24, Y+2 ; 0x02
f4: 88 2f mov r24, r24
f6: 90 e0 ldi r25, 0x00 ; 0
f8: 80 95 com r24
fa: 90 95 com r25
fc: 28 17 cp r18, r24
fe: 39 07 cpc r19, r25
100: 19 f4 brne .+6 ; 0x108 <main+0x3a>
p(tmp);
102: 89 81 ldd r24, Y+1 ; 0x01
104: 0e 94 5a 00 call 0xb4 ; 0xb4 <p>
tmp = ~XOR;
108: 8a 81 ldd r24, Y+2 ; 0x02
10a: 80 95 com r24
10c: 89 83 std Y+1, r24 ; 0x01
if (g() == tmp)
10e: 0e 94 52 00 call 0xa4 ; 0xa4 <g>
112: 98 2f mov r25, r24
114: 89 81 ldd r24, Y+1 ; 0x01
116: 98 17 cp r25, r24
118: 19 f4 brne .+6 ; 0x120 <main+0x52>
p(tmp);
11a: 89 81 ldd r24, Y+1 ; 0x01
11c: 0e 94 5a 00 call 0xb4 ; 0xb4 <p>
--
Summary: [avr] conditional comparison uses short instead of char
Product: gcc
Version: 4.3.2
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: najay at najay dot com
GCC host triplet: x86
GCC target triplet: avr-*-*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40935
