unsigned OptSub2 (CodeSeg* S)
/* Search for the sequence
**
** lda xx
** sec
** sta tmp1
** lda yy
** sbc tmp1
** sta yy
**
** and replace it by
**
** sec
** lda yy
** sbc xx
** sta yy
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[5];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_LDA &&
!CS_RangeHasLabel (S, I+1, 5) &&
CS_GetEntries (S, L, I+1, 5) &&
L[0]->OPC == OP65_SEC &&
L[1]->OPC == OP65_STA &&
strcmp (L[1]->Arg, "tmp1") == 0 &&
L[2]->OPC == OP65_LDA &&
L[3]->OPC == OP65_SBC &&
strcmp (L[3]->Arg, "tmp1") == 0 &&
L[4]->OPC == OP65_STA &&
strcmp (L[4]->Arg, L[2]->Arg) == 0) {
/* Remove the store to tmp1 */
CS_DelEntry (S, I+2);
/* Remove the subtraction */
CS_DelEntry (S, I+3);
/* Move the lda to the position of the subtraction and change the
** op to SBC.
*/
CS_MoveEntry (S, I, I+3);
CE_ReplaceOPC (E, OP65_SBC);
/* If the sequence head had a label, move this label back to the
** head.
*/
if (CE_HasLabel (E)) {
CS_MoveLabels (S, E, L[0]);
}
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp4 (CodeSeg* S)
/* Search for
*
* lda x
* ldx y
* cpx #a
* bne L1
* cmp #b
* L1: jne/jeq L2
*
* If a is zero, we may remove the compare. If a and b are both zero, we may
* replace it by the sequence
*
* lda x
* ora x+1
* jne/jeq ...
*
* L1 may be either the label at the branch instruction, or the target label
* of this instruction.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[5];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_LDA &&
CS_GetEntries (S, L, I+1, 5) &&
L[0]->OPC == OP65_LDX &&
!CE_HasLabel (L[0]) &&
IsImmCmp16 (L+1) &&
!RegAXUsed (S, I+6)) {
if ((L[4]->Info & OF_FBRA) != 0 && L[1]->Num == 0 && L[3]->Num == 0) {
/* The value is zero, we may use the simple code version. */
CE_ReplaceOPC (L[0], OP65_ORA);
CS_DelEntries (S, I+2, 3);
} else {
/* Move the lda instruction after the first branch. This will
* improve speed, since the load is delayed after the first
* test.
*/
CS_MoveEntry (S, I, I+4);
/* We will replace the ldx/cpx by lda/cmp */
CE_ReplaceOPC (L[0], OP65_LDA);
CE_ReplaceOPC (L[1], OP65_CMP);
/* Beware: If the first LDA instruction had a label, we have
* to move this label to the top of the sequence again.
*/
if (CE_HasLabel (E)) {
CS_MoveLabels (S, E, L[0]);
}
}
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
