Can someone explain to me, this is a compilation error in the experimental
branch MSPGCC, or some feature of the compiler?
int main(void)
{
WDTCTL=WDTPW|WDTTMSEL|WDTSSEL|WDTIS0;
volatile uint8_t a, b, c;
a=0b10000111;
b=0b10000101;
if((a^b)&0x80) c=0xAA; //checking MSB (a xor b), must be 0
else c=0xBB;
if(c==0xAA) led_on();
/*
In experimental version of GCC (mspgcc-20120224-experimental) this condition
is TRUE, while should be FALSE.
Stable version mspgcc-20110716-p20111105 works correctly (condition is FALSE)
*/
}
ASM listing:
---mspgcc-20120224-experimental:
a=0b10000111;
cc8c: f1 40 87 ff mov.b #-121, 2(r1) ;#0xff87, 0x0002(r1)
cc90: 02 00
b=0b10000101;
cc92: f1 40 85 ff mov.b #-123, 1(r1) ;#0xff85, 0x0001(r1)
cc96: 01 00
if((a^b)&0x80) c=0xAA;
cc98: 5e 41 02 00 mov.b 2(r1), r14 ;0x0002(r1)
cc9c: 5f 41 01 00 mov.b 1(r1), r15 ;0x0001(r1)
cca0: 4f ee xor.b r14, r15
cca2: 04 34 jge $+10 ;abs 0xccac <---------
cca4: f1 40 aa ff mov.b #-86, 0(r1) ;#0xffaa, 0x0000(r1)
cca8: 00 00
ccaa: 03 3c jmp $+8 ;abs 0xccb2
else c=0xBB;
ccac: f1 40 bb ff mov.b #-69, 0(r1) ;#0xffbb, 0x0000(r1)
ccb0: 00 00
---mspgcc-20110716-p20111105:
a=0b10000111;
ccda: f1 40 87 ff mov.b #-121, 0(r1) ;#0xff87, 0x0000(r1)
ccde: 00 00
b=0b10000101;
cce0: f1 40 85 ff mov.b #-123, 1(r1) ;#0xff85, 0x0001(r1)
cce4: 01 00
if((a^b)&0x80) c=0xAA;
cce6: 5f 41 01 00 mov.b 1(r1), r15 ;0x0001(r1)
ccea: 6f e1 xor.b @r1, r15
ccec: 4f 93 tst.b r15 <---------
ccee: 04 34 jge $+10 ;abs 0xccf8
ccf0: f1 40 aa ff mov.b #-86, 2(r1) ;#0xffaa, 0x0002(r1)
ccf4: 02 00
ccf6: 03 3c jmp $+8 ;abs 0xccfe
else c=0xBB;
ccf8: f1 40 bb ff mov.b #-69, 2(r1) ;#0xffbb, 0x0002(r1)
ccfc: 02 00
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