[sdcc-devel] [ sdcc-Bugs-1605880 ] Assignment optimized out of critical block

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Bugs item #1605880, was opened at 2006-11-30 01:36
Message generated for change (Settings changed) made by epetrich
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Category: None
>Group: fixed
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Erik Petrich (epetrich)
Assigned to: Erik Petrich (epetrich)
Summary: Assignment optimized out of critical block

Initial Comment:
Since an update to a volatile variable is probably non-atomic, I've protected the assignment to it by enclosing the assignment within a __critical {} block. However, in some cases the assignment is optimized and moved to a point at which interrupts might still be enabled.

volatile int x;

void setx(int newx)
{
  __critical
    {
      x=newx;
    }
}

_setx:
;       genReceive
        mov     _x,dpl
        mov     (_x + 1),dph   ; assignment moved here
;       critical.c:9: }
;       genCritical
        setb    _test_sloc0_1_0
        jbc     ea,00103$
        clr     _test_sloc0_1_0
00103$:
;       critical.c:8: x=newx;
;     genEndCritical
        mov     c,_test_sloc0_1_0
        mov     ea,c
;       Peephole 300    removed redundant label 00101$
        ret

The above test code fails on SDCC #4492 for mcs51 (--model-small) and hc08, but not the z80.


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

>Comment By: Erik Petrich (epetrich)
Date: 2006-12-10 10:47

Message:
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user_id=635249
Originator: YES

Fixed in SDCC #4510


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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=100599&aid=1605880&group_id=599