[Sdcc-user] Local memory allocation problem?

[Joseph C. <jo...@jo...>]

Hi,

I suddenly started getting strange and noticed the following (I think) bug:

sdcc (2.3.0, windos) reuses registers more than once to store local
variables within a single function.

The problem code snippet has the following local variable defined:

void test_code (void) {
  unsigned int threshold;
  unsigned char count;
  unsigned int b;
  unsigned char ch;
  unsigned char sm;
  unsigned char prev;
  unsigned char i;
  int j;


The .lst shows the following register allocations:

;------------------------------------------------------------
                            268 ;Allocation info for local variables in
function 'test_code'
                            269
;------------------------------------------------------------
                            270 ;threshold                 Allocated to in
memory with name '_test_code_threshold_1_1'
                            271 ;count                     Allocated to
registers r2
                            272 ;b                         Allocated to
registers r5 r6
                            273 ;ch                        Allocated to
registers r3
                            274 ;sm                        Allocated to
registers r2
                            275 ;prev                      Allocated to
registers
                            276 ;i                         Allocated to
registers
                            277 ;j                         Allocated to in
memory with name '_test_code_j_1_1'
                            278 ;	setup.c 49
                            279 ;	-----------------------------------------
                            280 ;	 function test_code
                            281 ;	-----------------------------------------

Whoooaaa.  That ain't good.  I've been trying to see if there's anything
that I did on my side to tickle this behavior, but I don't see anything
obvious.  What's more troubling is that a number of these blank "allocated
to registers" also reuse the same registers.

The variable "i" is actually allocated to register r3 (according to the
.lst).
The variable "prev" is actually unused in my test code now.

Am I doing something wrong?  Or has anyone else seen this?

Many thanks,
Joseph