I had trouble with the 30 Jan 2010 and earlier versions of the PIC sdcc
compiler on the following code for the PIC4620:
oid RateRPG() {
char W_temp;
W_temp = PORTD; // Copy PORTD into W_temp
TEMP = W_temp; // and TEMP
W_temp = W_temp ^ OLDPORTD; // Any change?
W_temp = W_temp & 0b00000011; // If not, W_temp = 0
if (W_temp != 0){ // If the two bits have changed
then...
W_temp = OLDPORTD>>1; // Form what a CCW change would
produce
...
}
}
The compiler issued a:
BANKSEL (null)
which of course failed to compile. It also did not allocate W_temp, or
issue the code for:
W_temp = W_temp ^ OLDPORTD; // Any change?
W_temp = W_temp & 0b00000011; // If not, W_temp = 0
Interestingly, the code compiles correctly if W_temp is a global variable.
Some investigation revealed in ralloc.c at line 4148:
/* if the condition of an if instruction
is defined in the previous instruction then
mark the itemp as a conditional */
if ((IS_CONDITIONAL (ic) ||
((ic->op == BITWISEAND ||
ic->op == '|' ||
ic->op == '^') &&
isBitwiseOptimizable (ic))) &&
ic->next && ic->next->op == IFX &&
isOperandEqual (IC_RESULT (ic), IC_COND (ic->next)) &&
OP_SYMBOL (IC_RESULT (ic))->liveTo <= ic->next->seq)
{
debugLog (" %d\n", __LINE__);
OP_SYMBOL (IC_RESULT (ic))->regType = REG_CND;
continue;
}
Clearly the code is not expecting a tree at this point, only a variable.
Commenting this optimization out fixed the problem at the cost of
slightly less efficient conditional code as in:
ANDWF r0x00, F ;key=00b, flow seq=060
.line 480; p3.c if (W_temp != 0){ // If the two
bits have changed then...
MOVF r0x00, W ;key=00c, flow seq=060
BZ _00189_DS_ ;key=00d, flow seq=060
How do I get this patch into the sourceforge version of sdcc?
Thank you,
Paul Neelands
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