[Bug c/19835] New: [AVR] Loop variable gets widened to LONG instead of int

[andrewhutchinson at cox dot net]

GNU C version 4.0.0 20041205 (experimental) (avr)

Loop variable gets widened to LONG instead of unsigned int (or perhaps even
int). Seems we forgeot how big the target is?

Testcase:

struct S19 { unsigned char i[19]; };
void                                            
init (struct S19 *p, int i)                     
{                                               
  int j;                                        
  for (j = 0; j < 19; j++)                      
    p->i[j] = i + j;                            
}       


tree dump:


;; Function init (init)

init (p, i)
{
  long unsigned int ivtmp.3;

<bb 0>:
  ivtmp.3 = 0;

<L0>:;
  ((unsigned char *) ivtmp.3 + &p->i[0])->i[0] = (unsigned char) ivtmp.3 +
(unsigned char) (signed char) i;
  ivtmp.3 = ivtmp.3 + 1;
  if (ivtmp.3 != 19) goto <L0>; else goto <L2>;

<L2>:;
  return;

}

Not surprisingly, backend code reflects long (SImode) decrement and compare :

/* prologue: frame size=0 */
/* prologue end (size=0) */
        movw r26,r24
        ldi r18,lo8(0)
        ldi r19,hi8(0)
        ldi r20,hlo8(0)
        ldi r21,hhi8(0)
.L2:
        movw r30,r26
        add r30,r18
        adc r31,r19
        mov r24,r18
        add r24,r22
        st Z,r24
        subi r18,lo8(-(1))
        sbci r19,hi8(-(1))
        sbci r20,hlo8(-(1))
        sbci r21,hhi8(-(1))
        cpi r18,lo8(19)
        cpc r19,__zero_reg__
        cpc r20,__zero_reg__
        cpc r21,__zero_reg__
        brne .L2
/* epilogue: frame size=0 */
        ret

-- 
           Summary: [AVR] Loop variable gets widened to LONG instead of int
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: andrewhutchinson at cox dot net
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: cygwin
GCC target triplet: avr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19835