[Sdcc-user] Another optimization missing for the 8051 compiler

[Rod B. <ro...@te...>]

All,

I have the following code fragment:
unsigned int test0;
unsigned int test1;

if( 0 == test0 )
{
     test0 = 1;
}

if( !test1 )
{
     test1 = 1
}

The list output shows the following:
    0000 E5*00               113         mov     a,_test0
    0002 70 04               114         jnz     00109$
    0004 E5*01               115         mov     a,(_test0 + 1)
    0006 60 02               116         jz      00110$
    0008                     117 00109$:
    0008 80 06               118         sjmp    00102$
    000A                     119 00110$:
                             120 ;       test51.c:8: test0 = 1;
    000A 75*00 01            121         mov     _test0,#0x01
    000D E4                  122         clr     a
    000E F5*01               123         mov     (_test0 + 1),a
    0010                     124 00102$:
                             125 ;       test51.c:11: if( !test1 )
    0010 E5*02               126         mov     a,_test1
    0012 45*03               127         orl     a,(_test1 + 1)
                             128 ;       test51.c:13: test1 = 0;
    0014 70 04               129         jnz     00105$
    0016 F5*02               130         mov     _test1,a
    0018 F5*03               131         mov     (_test1 + 1),a


My question is why is the first 'if' statement not optimized to be the 
same as the 2nd if statement.  This is using an extra 4-code space bytes.

Lets not have any code stylistic comments I personally think the 1st if 
statement is clearer and that is what the companies coding standard 
mandates.

I currently don't need the missing 4-bytes of code space and will only 
note this in the delivery notes.

Regards,
Rod Boyce