cc65: Postincrementing is optimized wrong in some cases

In my project the following line of code is optimized wrong… see how the readpos post increment turns into a preincrement:

#define FILECOPY_BLOCKADDR 0x04c8
unsigned short readcnt;
unsigned char readpos;
;
; ((u8*)FILECOPY_BLOCKADDR)[readcnt++] = ((u8*)0xd702)[readpos++];
;
L0272:
    ; load readcount to a/x
    lda     _readcnt
    ldx     _readcnt+1
    ; save a/x
    sta     regsave
    stx     regsave+1
    ; inc a/x by one
    jsr     incax1
    ; store incremented value in readcount
    sta     _readcnt
    stx     _readcnt+1

    ; add saved value to 0x04c8 and store in sreg
    lda     #$C8
    clc
    adc     regsave
    sta     sreg
    lda     #$04
    adc     regsave+1
    sta     sreg+1
    
    ; increment readpos
    inc     _readpos
    ; add readpos to 0xd702 and store in ptr1
    ldx     #$D7
    lda     #$02
    clc
    adc     _readpos
    bcc     L0333
    inx
L0333:    
    sta     ptr1
    stx     ptr1+1
    
    ldy     #$00
    lda     (ptr1),y
    sta     (sreg),y

i compile using the following options:

DEFS=--add-source
DEFS+=--local-strings
OPTS=-Or
OPTS+=-Oi
OPTS+=-Os
OPTS+=--codesize 180
OPTS+=-W const-comparison,no-effect,struct-param,unknown-pragma,unused-label,unused-param,unused-var

leaving out the --codesize option “fixes” it, ie that is the source of the wrong optimization

Since i know for sure that it worked like this a while ago, i will start binsearching for the offending commit… stay tuned 😃