#2539 expression with bool result assigned to bitfield generates wrong code

[Heinz Saathoff]

Code generated in following example only tests for bit #0

struct sBITS {
   unsigned  b0 : 1;
   unsigned  b1 : 1;
   unsigned  b2 : 1;
   unsigned  b3 : 1;
   unsigned  b4 : 1;
   unsigned  b5 : 1;
   unsigned  b6 : 1;
   unsigned  b7 : 1;
};
struct sBITS vb;
__bit  not_0;

void SetIf(uint8_t x) {
   vb.b3 = (x != 0); // only bit 0 of 'x' testet
   not_0 = (x != 0);  // works
}   

void main() {
   SetIf(13);
}

Resulting Code (from rst-file)

_SetIf:
    mov r7,dpl
;   sd1.c:17: vb.b3 = (x != 0); // only bit 0 of 'x' testet
    mov r0,#_vb
    mov a,r7
    rrc a           ; <-- BUG: only bit 0 tested
    mov a,@r0
    mov acc.3,c
    mov @r0,a
;   sd1.c:18: not_0 = (x != 0);  // works
    mov a,r7
    add a,#0xff
    mov _not_0,c
    ret

Compiler Version:
SDCC : mcs51/z80/z180/r2k/r3ka/gbz80/tlcs90/ds390/pic16/pic14/TININative/ds400/hc08/s08/stm8 3.6.0 #9615 (MINGW32)

command to compile:
sdcc.exe -mmcs51 --std-sdcc99 sample.c

• Heinz

[Philipp Klaus Krause]

I can reproduce the issue in sdcc 3.6.1 #9667. And it really is mcs51-specific: The code for stm8 and z80 looks okay.

Philipp

[Ben Shi]

I am afraid this is a bug will affect all ports.

The following test case fails.

/* bug-2539.c
  */

#include <testfwk.h>
#include <stdlib.h>

struct sBITS {
   unsigned  b0 : 1;
   unsigned  b1 : 1;
   unsigned  b2 : 1;
   unsigned  b3 : 1;
   unsigned  b4 : 1;
   unsigned  b5 : 1;
   unsigned  b6 : 1;
   unsigned  b7 : 1;
};
struct sBITS vb;

void SetIf(char x) {
   vb.b3 = (x != 0); // only bit 0 of 'x' testet
}

void
testBug(void)
{
        vb.b3 = 0;
        SetIf(0x60);
        ASSERT(vb.b3 == 1);

        vb.b3 = 0;

       SetIf(0x02);
        ASSERT(vb.b3 == 1);
}

Here is the wrong AST

Ben@Ben-PC /cygdrive/d/sdcc/qwe
$ sdcc a.c -c --dump-ast
FUNCTION (_SetIf=0x60016a140) type (void fixed) args (unsigned-char fixed)
tree (0x60016a0a0) not decorated
(null):0:{ L1 B0
(null):0:  DECLARE SYMBOL (L1 B1 x=0x6001695a0) type (unsigned-char fixed)
a.c:14:  ASSIGN(=) (0x600169460) type (unsigned-bitfield {3,1} data)
a.c:14:    PTR_ACCESS (0x600168d00) type (unsigned-bitfield {3,1} data)
a.c:14:      ADDRESS_OF (0x600168c60) type (struct sBITS near* fixed)
a.c:14:        SYMBOL (L0 B0 vb=0x600168580 @ 0x600166f30) type (struct sBITS fixed)
a.c:14:      SYMBOL (L1 B2 b3=0x600168bc0 @ 0x600168870)
a.c:14:    SYMBOL (L1 B1 x=0x6001690f0 @ 0x600167990) type (unsigned-char fixed)
(null):0:}

Ben@Ben-PC /cygdrive/d/sdcc/qwe
$ cat a.c
struct sBITS {
   unsigned  b0 : 1;
   unsigned  b1 : 1;
   unsigned  b2 : 1;
   unsigned  b3 : 1;
   unsigned  b4 : 1;
   unsigned  b5 : 1;
   unsigned  b6 : 1;
   unsigned  b7 : 1;
};
struct sBITS vb;

void SetIf(char x) {
   vb.b3 = (x != 0); // only bit 0 of 'x' testet
}

[Philipp Klaus Krause]

Seems this got fixed with the double negation stuff a while ago. To be sure it doesn't come back I added a test in rev. #9873.

Philipp