Technical information

Operating Precautions for CPDW9X/NT-CDR-V85X, Y-GHS-MULTI-V800

Customer Notification r20tu0003ed1812 38

No. a29

Wrong optimization for "Common-subexpr elimination”

Version Information

V3.5.1

Details

The compiler generates incorrect accesses to a volatile object. The problem only arises when the

set1 / clr1 instructions are used.

Example: test.c:

typedef struct Outputs_T {

unsigned char High:1 ;

unsigned char Low:1 ; } Outputs_T;

struct st_P3

{ unsigned int P30_b :1;

unsigned int P31_b :1;

unsigned int P32_b :1;

unsigned int P33_b :1;

unsigned int P34_b :1;

unsigned int P35_b :1;

unsigned int P36_b :1;

unsigned int P37_b :1;

unsigned int P38_b :1;

unsigned int P39_b :1;};

struct st_P5

{ unsigned int P50_b :1;

unsigned int P51_b :1;

unsigned int P52_b :1;

unsigned int P53_b :1;

unsigned int P54_b :1;

unsigned int P55_b :1;};

struct st_SFR

{ struct st_P3 P3;

struct st_P5 P5;};

volatile struct st_SFR REG;

void Output(Outputs_T APOut)

{

REG.P3.P39_b =3D APOut.High;

REG.P5.P50_b =3D APOut.Low;

}

void main(void)

{

Outputs_T a;

while(1) { Output(a); }

}