[sdcc-devel] [ sdcc-Bugs-1292721 ] variable load wrongly optimized away

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Bugs item #1292721, was opened at 2005-09-16 11:30
Message generated for change (Comment added) made by spth
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Category: z80 port
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Thomas Tensi (ttensi)
Assigned to: Nobody/Anonymous (nobody)
Summary: variable load wrongly optimized away

Initial Comment:
Dear all,


I am not sure if this is Z80 port related at all, but for
the following code SDCC#1076 produces wrong code:

====================
#include <string.h>

typedef unsigned char UINT8;
typedef signed char INT8;

void globalReplace (char *st, char *pattern, char 
*replacement)
  /* replaces all occurrences of <pattern> in <st> by 
<replacement> */
{
  UINT8 replacementLength = strlen(replacement);
  INT8 shiftOffset = replacementLength - strlen(pattern);

  for (;;) {
    /* find the first position of pattern */
    char *ptr = strstr(st, pattern);

    if (ptr == NULL) {
      break;
    } else {
      /* do an in-place character shift by shiftOffset */
      if (shiftOffset == 0) {
	/* no shift */
      } else {
        ...
      }
      ...
    }
    ...
  }
  ...
}
====================

The Z80 assembler code (with the i-code wrapped 
around for
clarity) looks like this:

====================
;sdcc-bug3.c:17: if (ptr == NULL) {
;
;ic:20:	iTemp12 [k22 lr19:20 so:0]{ ia0 a2p0 re0 rm0 
nos0 ru0 dp0}
;       {char} = iTemp8 [k15 lr18:50 so:0]{ ia0 a2p0 re1 
rm0 nos0
;       ru0 dp0}{char generic* }{ sir@ 
_globalReplace_ptr_2_2}
;       [_globalReplace_ptr_2_2] == 0x0 {void literal-
generic* }
;
;	genCmpEq
;	AOP_STK for _globalReplace_ptr_2_2
; genCmpEq: left 2, right 2, result 0
	ld	a,-4(ix)
	or	a,-3(ix)
	jp	z,00113$
00121$:

;ic:21: if iTemp12 [k22 lr19:20 so:0]{ ia0 a2p0 re0 rm0 
nos0 ru0
        dp0}{char} != 0 goto _return($13)

;sdcc-bug3.c:21: if (shiftOffset == 0) {
;
;ic:28: if iTemp13 [k23 lr13:52 so:0]{ ia0 a2p0 re0 rm0
;       nos0 ru0 dp0}{char} != 0 goto _ifend_1($6)
;
;	genIfx
	or	a,a
	jp	nz,00106$
====================

This means that the variable <shiftOffset> is not loaded,
but the compiler seems to assume it is already in the
accumulator.

Any ideas on that?


	  Best regards

	       Thomas



----------------------------------------------------------------------

Comment By: Philipp Krause (spth)
Date: 2007-04-15 01:13

Message:
Logged In: YES 
user_id=564030
Originator: NO

I can not reproduce this problem in sdcc  2.6.5 #4749.

----------------------------------------------------------------------

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