[sdcc-devel] [ sdcc-Bugs-861580 ] unnecessary "mov a,_i"

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Bugs item #861580, was opened at 2003-12-17 05:39
Message generated for change (Comment added) made by epetrich
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=100599&aid=861580&group_id=599

Category: None
>Group: fixed
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Jarek Zych (zych)
>Assigned to: Erik Petrich (epetrich)
Summary: unnecessary "mov a,_i"

Initial Comment:
volatile unsigned char i;
void external0_isr(void) interrupt 0
{
	i++;
}

If you use volatile keyword, compiler generates 
unnecessary "mov	a,_i"  instruction.
("++i"  do OK!)

_external0_isr:
	push	acc
	push	b
	push	dpl
	push	dph
	push	psw
	mov	psw,#0x00
;test.c:17: i++;
;     genDummyRead
	mov	a,_i			<<<<<!!!!!
;     genPlus
;     genPlusIncr
	inc	_i
00101$:
	pop	psw
	pop	dph
	pop	dpl
	pop	b
	pop	acc
	reti
	
SDCC : 
mcs51/gbz80/z80/avr/ds390/pic16/pic14/TININative/xa51
/ds400/hc08 2.3.6 (Dec 13 2003) (MINGW32)


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>Comment By: Erik Petrich (epetrich)
Date: 2003-12-20 01:22

Message:
Logged In: YES 
user_id=635249

Fixed; see ChangeLog 1.540 for the list of files updated.

This was rather tricky to fix since
  y=x++;
is very nearly the same as 
  y=x; ++x;


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https://sourceforge.net/tracker/?func=detail&atid=100599&aid=861580&group_id=599