unsigned OptBNegAX1 (CodeSeg* S)
/* On a call to bnegax, if X is zero, the result depends only on the value in
* A, so change the call to a call to bnega. This will get further optimized
* later if possible.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check if this is a call to bnegax, and if X is known and zero */
if (E->RI->In.RegX == 0 && CE_IsCallTo (E, "bnegax")) {
CodeEntry* X = NewCodeEntry (OP65_JSR, AM65_ABS, "bnega", 0, E->LI);
CS_InsertEntry (S, X, I+1);
CS_DelEntry (S, I);
/* We had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp6 (CodeSeg* S)
/* Search for calls to compare subroutines followed by a conditional branch
* and replace them by cheaper versions, since the branch means that the
* boolean value returned by these routines is not needed (we may also check
* that explicitly, but for the current code generator it is always true).
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* N;
cmp_t Cond;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_JSR &&
(Cond = FindTosCmpCond (E->Arg)) != CMP_INV &&
(N = CS_GetNextEntry (S, I)) != 0 &&
(N->Info & OF_ZBRA) != 0 &&
!CE_HasLabel (N)) {
/* The tos... functions will return a boolean value in a/x and
* the Z flag says if this value is zero or not. We will call
* a cheaper subroutine instead, one that does not return a
* boolean value but only valid flags. Note: jeq jumps if
* the condition is not met, jne jumps if the condition is met.
* Invert the code if we jump on condition not met.
*/
if (GetBranchCond (N->OPC) == BC_EQ) {
/* Jumps if condition false, invert condition */
Cond = CmpInvertTab [Cond];
}
/* Replace the subroutine call. */
E = NewCodeEntry (OP65_JSR, AM65_ABS, "tosicmp", 0, E->LI);
CS_InsertEntry (S, E, I+1);
CS_DelEntry (S, I);
/* Replace the conditional branch */
ReplaceCmp (S, I+1, Cond);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptShift2(CodeSeg* S)
/* A call to the asrax1 routines may get replaced by something simpler, if
* X is not used later:
*
* cmp #$80
* ror a
*
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
unsigned Shift;
unsigned Count;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_JSR &&
(Shift = GetShift (E->Arg)) != SHIFT_NONE &&
SHIFT_TYPE (Shift) == SHIFT_TYPE_ASR &&
(Count = SHIFT_COUNT (Shift)) > 0 &&
Count * 100 <= S->CodeSizeFactor &&
!RegXUsed (S, I+1)) {
CodeEntry* X;
unsigned J = I+1;
/* Generate the replacement sequence */
while (Count--) {
/* cmp #$80 */
X = NewCodeEntry (OP65_CMP, AM65_IMM, "$80", 0, E->LI);
CS_InsertEntry (S, X, J++);
/* ror a */
X = NewCodeEntry (OP65_ROR, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, J++);
}
/* Delete the call to asrax */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptBNegAX3 (CodeSeg* S)
/* Search for the sequence:
*
* lda xx
* ldx yy
* jsr bnegax
* jne/jeq ...
*
* and replace it by
*
* lda xx
* ora xx+1
* jeq/jne ...
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[3];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_LDA &&
CS_GetEntries (S, L, I+1, 3) &&
L[0]->OPC == OP65_LDX &&
!CE_HasLabel (L[0]) &&
CE_IsCallTo (L[1], "bnegax") &&
!CE_HasLabel (L[1]) &&
(L[2]->Info & OF_ZBRA) != 0 &&
!CE_HasLabel (L[2])) {
/* ldx --> ora */
CE_ReplaceOPC (L[0], OP65_ORA);
/* Invert the branch */
CE_ReplaceOPC (L[2], GetInverseBranch (L[2]->OPC));
/* Delete the subroutine call */
CS_DelEntry (S, I+2);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptBNegA2 (CodeSeg* S)
/* Check for
*
* lda ..
* jsr bnega
* jeq/jne ..
*
* Adjust the conditional branch and remove the call to the subroutine.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[2];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if ((E->OPC == OP65_ADC ||
E->OPC == OP65_AND ||
E->OPC == OP65_DEA ||
E->OPC == OP65_EOR ||
E->OPC == OP65_INA ||
E->OPC == OP65_LDA ||
E->OPC == OP65_ORA ||
E->OPC == OP65_PLA ||
E->OPC == OP65_SBC ||
E->OPC == OP65_TXA ||
E->OPC == OP65_TYA) &&
CS_GetEntries (S, L, I+1, 2) &&
CE_IsCallTo (L[0], "bnega") &&
!CE_HasLabel (L[0]) &&
(L[1]->Info & OF_ZBRA) != 0 &&
!CE_HasLabel (L[1])) {
/* Invert the branch */
CE_ReplaceOPC (L[1], GetInverseBranch (L[1]->OPC));
/* Delete the subroutine call */
CS_DelEntry (S, I+1);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptNegAX1 (CodeSeg* S)
/* Search for a call to negax and replace it by
*
* eor #$FF
* clc
* adc #$01
*
* if X isn't used later.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check if this is a call to negax, and if X isn't used later */
if (CE_IsCallTo (E, "negax") && !RegXUsed (S, I+1)) {
CodeEntry* X;
/* Add replacement code behind */
X = NewCodeEntry (OP65_EOR, AM65_IMM, "$FF", 0, E->LI);
CS_InsertEntry (S, X, I+1);
X = NewCodeEntry (OP65_CLC, AM65_IMP, 0, 0, E->LI);
CS_InsertEntry (S, X, I+2);
X = NewCodeEntry (OP65_ADC, AM65_IMM, "$01", 0, E->LI);
CS_InsertEntry (S, X, I+3);
/* Delete the call to negax */
CS_DelEntry (S, I);
/* Skip the generated code */
I += 2;
/* We had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptBoolTrans (CodeSeg* S)
/* Try to remove the call to boolean transformer routines where the call is
* not really needed.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* N;
cmp_t Cond;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for a boolean transformer */
if (E->OPC == OP65_JSR &&
(Cond = FindBoolCmpCond (E->Arg)) != CMP_INV &&
(N = CS_GetNextEntry (S, I)) != 0 &&
(N->Info & OF_ZBRA) != 0) {
/* Make the boolean transformer unnecessary by changing the
* the conditional jump to evaluate the condition flags that
* are set after the compare directly. Note: jeq jumps if
* the condition is not met, jne jumps if the condition is met.
* Invert the code if we jump on condition not met.
*/
if (GetBranchCond (N->OPC) == BC_EQ) {
/* Jumps if condition false, invert condition */
Cond = CmpInvertTab [Cond];
}
/* Check if we can replace the code by something better */
ReplaceCmp (S, I+1, Cond);
/* Remove the call to the bool transformer */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
void CS_DelEntries (CodeSeg* S, unsigned Start, unsigned Count)
/* Delete a range of code entries. This includes removing references to labels,
* labels attached to the entries and so on.
*/
{
/* Start deleting the entries from the rear, because this involves less
* memory moving.
*/
while (Count--) {
CS_DelEntry (S, Start + Count);
}
}
unsigned OptSub3 (CodeSeg* S)
/* Search for a call to decaxn and replace it by an 8 bit sub if the X register
** is not used later.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* E;
/* Get next entry */
E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_JSR &&
strncmp (E->Arg, "decax", 5) == 0 &&
IsDigit (E->Arg[5]) &&
E->Arg[6] == '\0' &&
!RegXUsed (S, I+1)) {
CodeEntry* X;
const char* Arg;
/* Insert new code behind the sequence */
X = NewCodeEntry (OP65_SEC, AM65_IMP, 0, 0, E->LI);
CS_InsertEntry (S, X, I+1);
Arg = MakeHexArg (E->Arg[5] - '0');
X = NewCodeEntry (OP65_SBC, AM65_IMM, Arg, 0, E->LI);
CS_InsertEntry (S, X, I+2);
/* Delete the old code */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
static unsigned OptLoad1 (CodeSeg* S)
/* Search for a call to ldaxysp where X is not used later and replace it by
** a load of just the A register.
*/
{
unsigned I;
unsigned Changes = 0;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* E;
/* Get next entry */
E = CS_GetEntry (S, I);
/* Check for the sequence */
if (CE_IsCallTo (E, "ldaxysp") &&
RegValIsKnown (E->RI->In.RegY) &&
!RegXUsed (S, I+1)) {
CodeEntry* X;
/* Reload the Y register */
const char* Arg = MakeHexArg (E->RI->In.RegY - 1);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
CS_InsertEntry (S, X, I+1);
/* Load from stack */
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, E->LI);
CS_InsertEntry (S, X, I+2);
/* Now remove the call to the subroutine */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptBNegA1 (CodeSeg* S)
/* Check for
*
* ldx #$00
* lda ..
* jsr bnega
*
* Remove the ldx if the lda does not use it.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[2];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for a ldx */
if (E->OPC == OP65_LDX &&
E->AM == AM65_IMM &&
(E->Flags & CEF_NUMARG) != 0 &&
E->Num == 0 &&
CS_GetEntries (S, L, I+1, 2) &&
L[0]->OPC == OP65_LDA &&
(L[0]->Use & REG_X) == 0 &&
!CE_HasLabel (L[0]) &&
CE_IsCallTo (L[1], "bnega") &&
!CE_HasLabel (L[1])) {
/* Remove the ldx instruction */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned Opt65C02Stores (CodeSeg* S)
/* Use STZ where possible */
{
unsigned Changes = 0;
unsigned I;
/* Generate register info for this step */
CS_GenRegInfo (S);
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for a store with a register value of zero and an addressing
* mode available with STZ.
*/
if (((E->OPC == OP65_STA && E->RI->In.RegA == 0) ||
(E->OPC == OP65_STX && E->RI->In.RegX == 0) ||
(E->OPC == OP65_STY && E->RI->In.RegY == 0)) &&
(E->AM == AM65_ZP || E->AM == AM65_ABS ||
E->AM == AM65_ZPX || E->AM == AM65_ABSX)) {
/* Replace by STZ */
CodeEntry* X = NewCodeEntry (OP65_STZ, E->AM, E->Arg, 0, E->LI);
CS_InsertEntry (S, X, I+1);
/* Delete the old stuff */
CS_DelEntry (S, I);
/* We had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Free register info */
CS_FreeRegInfo (S);
/* Return the number of changes made */
return Changes;
}
unsigned Opt65C02Ind (CodeSeg* S)
/* Try to use the indirect addressing mode where possible */
{
unsigned Changes = 0;
unsigned I;
/* Generate register info for this step */
CS_GenRegInfo (S);
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for addressing mode indirect indexed Y where Y is zero.
* Note: All opcodes that are available as (zp),y are also available
* as (zp), so we can ignore the actual opcode here.
*/
if (E->AM == AM65_ZP_INDY && E->RI->In.RegY == 0) {
/* Replace it by indirect addressing mode */
CodeEntry* X = NewCodeEntry (E->OPC, AM65_ZP_IND, E->Arg, 0, E->LI);
CS_InsertEntry (S, X, I+1);
CS_DelEntry (S, I);
/* We had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Free register info */
CS_FreeRegInfo (S);
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp7 (CodeSeg* S)
/* Search for a sequence ldx/txa/branch and remove the txa if A is not
* used later.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[2];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if ((E->OPC == OP65_LDX) &&
CS_GetEntries (S, L, I+1, 2) &&
L[0]->OPC == OP65_TXA &&
!CE_HasLabel (L[0]) &&
(L[1]->Info & OF_FBRA) != 0 &&
!CE_HasLabel (L[1]) &&
!RegAUsed (S, I+3)) {
/* Remove the txa */
CS_DelEntry (S, I+1);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptTest2 (CodeSeg* S)
/* Search for an inc/dec operation followed by a load and a conditional
* branch based on the flags from the load. Remove the load if the insn
* isn't used later.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[3];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check if it's the sequence we're searching for */
if ((L[0]->OPC == OP65_INC || L[0]->OPC == OP65_DEC) &&
CS_GetEntries (S, L+1, I+1, 2) &&
!CE_HasLabel (L[1]) &&
(L[1]->Info & OF_LOAD) != 0 &&
(L[2]->Info & OF_FBRA) != 0 &&
L[1]->AM == L[0]->AM &&
strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
(GetRegInfo (S, I+2, L[1]->Chg) & L[1]->Chg) == 0) {
/* Remove the load */
CS_DelEntry (S, I+1);
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
static unsigned OptDecouple (CodeSeg* S)
/* Decouple operations, that is, do the following replacements:
**
** dex -> ldx #imm
** inx -> ldx #imm
** dey -> ldy #imm
** iny -> ldy #imm
** tax -> ldx #imm
** txa -> lda #imm
** tay -> ldy #imm
** tya -> lda #imm
** lda zp -> lda #imm
** ldx zp -> ldx #imm
** ldy zp -> ldy #imm
**
** Provided that the register values are known of course.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
const char* Arg;
/* Get next entry and it's input register values */
CodeEntry* E = CS_GetEntry (S, I);
const RegContents* In = &E->RI->In;
/* Assume we have no replacement */
CodeEntry* X = 0;
/* Check the instruction */
switch (E->OPC) {
case OP65_DEA:
if (RegValIsKnown (In->RegA)) {
Arg = MakeHexArg ((In->RegA - 1) & 0xFF);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_DEX:
if (RegValIsKnown (In->RegX)) {
Arg = MakeHexArg ((In->RegX - 1) & 0xFF);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_DEY:
if (RegValIsKnown (In->RegY)) {
Arg = MakeHexArg ((In->RegY - 1) & 0xFF);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_INA:
if (RegValIsKnown (In->RegA)) {
Arg = MakeHexArg ((In->RegA + 1) & 0xFF);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_INX:
if (RegValIsKnown (In->RegX)) {
Arg = MakeHexArg ((In->RegX + 1) & 0xFF);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_INY:
if (RegValIsKnown (In->RegY)) {
Arg = MakeHexArg ((In->RegY + 1) & 0xFF);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_LDA:
if (E->AM == AM65_ZP) {
switch (GetKnownReg (E->Use & REG_ZP, In)) {
case REG_TMP1:
Arg = MakeHexArg (In->Tmp1);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
break;
case REG_PTR1_LO:
Arg = MakeHexArg (In->Ptr1Lo);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
break;
case REG_PTR1_HI:
Arg = MakeHexArg (In->Ptr1Hi);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
break;
case REG_SREG_LO:
Arg = MakeHexArg (In->SRegLo);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
break;
case REG_SREG_HI:
Arg = MakeHexArg (In->SRegHi);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
break;
}
}
break;
case OP65_LDX:
if (E->AM == AM65_ZP) {
switch (GetKnownReg (E->Use & REG_ZP, In)) {
case REG_TMP1:
Arg = MakeHexArg (In->Tmp1);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
break;
case REG_PTR1_LO:
Arg = MakeHexArg (In->Ptr1Lo);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
break;
case REG_PTR1_HI:
Arg = MakeHexArg (In->Ptr1Hi);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
break;
case REG_SREG_LO:
Arg = MakeHexArg (In->SRegLo);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
break;
case REG_SREG_HI:
Arg = MakeHexArg (In->SRegHi);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
break;
}
}
break;
case OP65_LDY:
if (E->AM == AM65_ZP) {
switch (GetKnownReg (E->Use, In)) {
case REG_TMP1:
Arg = MakeHexArg (In->Tmp1);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
break;
case REG_PTR1_LO:
Arg = MakeHexArg (In->Ptr1Lo);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
break;
case REG_PTR1_HI:
Arg = MakeHexArg (In->Ptr1Hi);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
break;
case REG_SREG_LO:
Arg = MakeHexArg (In->SRegLo);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
break;
case REG_SREG_HI:
Arg = MakeHexArg (In->SRegHi);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
break;
}
}
break;
case OP65_TAX:
if (E->RI->In.RegA >= 0) {
Arg = MakeHexArg (In->RegA);
X = NewCodeEntry (OP65_LDX, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_TAY:
if (E->RI->In.RegA >= 0) {
Arg = MakeHexArg (In->RegA);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_TXA:
if (E->RI->In.RegX >= 0) {
Arg = MakeHexArg (In->RegX);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
}
break;
case OP65_TYA:
if (E->RI->In.RegY >= 0) {
Arg = MakeHexArg (In->RegY);
X = NewCodeEntry (OP65_LDA, AM65_IMM, Arg, 0, E->LI);
}
break;
default:
/* Avoid gcc warnings */
break;
}
/* Insert the replacement if we have one */
if (X) {
CS_InsertEntry (S, X, I+1);
CS_DelEntry (S, I);
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptTest1 (CodeSeg* S)
/* Given a sequence
*
* stx xxx
* ora xxx
* beq/bne ...
*
* If X is zero, the sequence may be changed to
*
* cmp #$00
* beq/bne ...
*
* which may be optimized further by another step.
*
* If A is zero, the sequence may be changed to
*
* txa
* beq/bne ...
*
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[3];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check if it's the sequence we're searching for */
if (L[0]->OPC == OP65_STX &&
CS_GetEntries (S, L+1, I+1, 2) &&
!CE_HasLabel (L[1]) &&
L[1]->OPC == OP65_ORA &&
strcmp (L[0]->Arg, L[1]->Arg) == 0 &&
!CE_HasLabel (L[2]) &&
(L[2]->Info & OF_ZBRA) != 0) {
/* Check if X is zero */
if (L[0]->RI->In.RegX == 0) {
/* Insert the compare */
CodeEntry* N = NewCodeEntry (OP65_CMP, AM65_IMM, "$00", 0, L[0]->LI);
CS_InsertEntry (S, N, I+2);
/* Remove the two other insns */
CS_DelEntry (S, I+1);
CS_DelEntry (S, I);
/* We had changes */
++Changes;
/* Check if A is zero */
} else if (L[1]->RI->In.RegA == 0) {
/* Insert the txa */
CodeEntry* N = NewCodeEntry (OP65_TXA, AM65_IMP, 0, 0, L[1]->LI);
CS_InsertEntry (S, N, I+2);
/* Remove the two other insns */
CS_DelEntry (S, I+1);
CS_DelEntry (S, I);
/* We had changes */
++Changes;
}
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
static unsigned OptLoad2 (CodeSeg* S)
/* Replace calls to ldaxysp by inline code */
{
unsigned I;
unsigned Changes = 0;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[3];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if (CE_IsCallTo (L[0], "ldaxysp")) {
CodeEntry* X;
/* Followed by sta abs/stx abs? */
if (CS_GetEntries (S, L+1, I+1, 2) &&
L[1]->OPC == OP65_STA &&
L[2]->OPC == OP65_STX &&
(L[1]->Arg == 0 ||
L[2]->Arg == 0 ||
strcmp (L[1]->Arg, L[2]->Arg) != 0) &&
!CS_RangeHasLabel (S, I+1, 2) &&
!RegXUsed (S, I+3)) {
/* A/X are stored into memory somewhere and X is not used
** later
*/
/* lda (sp),y */
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[0]->LI);
CS_InsertEntry (S, X, I+3);
/* sta abs */
X = NewCodeEntry (OP65_STA, L[2]->AM, L[2]->Arg, 0, L[2]->LI);
CS_InsertEntry (S, X, I+4);
/* dey */
X = NewCodeEntry (OP65_DEY, AM65_IMP, 0, 0, L[0]->LI);
CS_InsertEntry (S, X, I+5);
/* lda (sp),y */
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[0]->LI);
CS_InsertEntry (S, X, I+6);
/* sta abs */
X = NewCodeEntry (OP65_STA, L[1]->AM, L[1]->Arg, 0, L[1]->LI);
CS_InsertEntry (S, X, I+7);
/* Now remove the call to the subroutine and the sta/stx */
CS_DelEntries (S, I, 3);
} else {
/* Standard replacement */
/* lda (sp),y */
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[0]->LI);
CS_InsertEntry (S, X, I+1);
/* tax */
X = NewCodeEntry (OP65_TAX, AM65_IMP, 0, 0, L[0]->LI);
CS_InsertEntry (S, X, I+2);
/* dey */
X = NewCodeEntry (OP65_DEY, AM65_IMP, 0, 0, L[0]->LI);
CS_InsertEntry (S, X, I+3);
/* lda (sp),y */
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[0]->LI);
CS_InsertEntry (S, X, I+4);
/* Now remove the call to the subroutine */
CS_DelEntry (S, I);
}
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
static unsigned OptLoad3 (CodeSeg* S)
/* Remove repeated loads from one and the same memory location */
{
unsigned Changes = 0;
CodeEntry* Load = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Forget a preceeding load if we have a label */
if (Load && CE_HasLabel (E)) {
Load = 0;
}
/* Check if this insn is a load */
if (E->Info & OF_LOAD) {
CodeEntry* N;
/* If we had a preceeding load that is identical, remove this one.
** If it is not identical, or we didn't have one, remember it.
*/
if (Load != 0 &&
E->OPC == Load->OPC &&
E->AM == Load->AM &&
((E->Arg == 0 && Load->Arg == 0) ||
strcmp (E->Arg, Load->Arg) == 0) &&
(N = CS_GetNextEntry (S, I)) != 0 &&
(N->Info & OF_CBRA) == 0) {
/* Now remove the call to the subroutine */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
/* Next insn */
continue;
} else {
Load = E;
}
} else if ((E->Info & OF_CMP) == 0 && (E->Info & OF_CBRA) == 0) {
/* Forget the first load on occurance of any insn we don't like */
Load = 0;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptNegAX2 (CodeSeg* S)
/* Search for a call to negax and replace it by
*
* ldx #$FF
* eor #$FF
* clc
* adc #$01
* bne L1
* inx
* L1:
*
* if X is known and zero on entry.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* P;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check if this is a call to negax, and if X is known and zero */
if (E->RI->In.RegX == 0 &&
CE_IsCallTo (E, "negax") &&
(P = CS_GetNextEntry (S, I)) != 0) {
CodeEntry* X;
CodeLabel* L;
/* Add replacement code behind */
/* ldx #$FF */
X = NewCodeEntry (OP65_LDX, AM65_IMM, "$FF", 0, E->LI);
CS_InsertEntry (S, X, I+1);
/* eor #$FF */
X = NewCodeEntry (OP65_EOR, AM65_IMM, "$FF", 0, E->LI);
CS_InsertEntry (S, X, I+2);
/* clc */
X = NewCodeEntry (OP65_CLC, AM65_IMP, 0, 0, E->LI);
CS_InsertEntry (S, X, I+3);
/* adc #$01 */
X = NewCodeEntry (OP65_ADC, AM65_IMM, "$01", 0, E->LI);
CS_InsertEntry (S, X, I+4);
/* Get the label attached to the insn following the call */
L = CS_GenLabel (S, P);
/* bne L */
X = NewCodeEntry (OP65_BNE, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, X, I+5);
/* inx */
X = NewCodeEntry (OP65_INX, AM65_IMP, 0, 0, E->LI);
CS_InsertEntry (S, X, I+6);
/* Delete the call to negax */
CS_DelEntry (S, I);
/* Skip the generated code */
I += 5;
/* We had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp9 (CodeSeg* S)
/* Search for the sequence
*
* sbc xx
* bvs/bvc L
* eor #$80
* L: asl a
* bcc/bcs somewhere
*
* If A is not used later (which should be the case), we can branch on the N
* flag instead of the carry flag and remove the asl.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[5];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if (L[0]->OPC == OP65_SBC &&
CS_GetEntries (S, L+1, I+1, 4) &&
(L[1]->OPC == OP65_BVC ||
L[1]->OPC == OP65_BVS) &&
L[1]->JumpTo != 0 &&
L[1]->JumpTo->Owner == L[3] &&
L[2]->OPC == OP65_EOR &&
CE_IsKnownImm (L[2], 0x80) &&
L[3]->OPC == OP65_ASL &&
L[3]->AM == AM65_ACC &&
(L[4]->OPC == OP65_BCC ||
L[4]->OPC == OP65_BCS ||
L[4]->OPC == OP65_JCC ||
L[4]->OPC == OP65_JCS) &&
!CE_HasLabel (L[4]) &&
!RegAUsed (S, I+4)) {
/* Replace the branch condition */
switch (GetBranchCond (L[4]->OPC)) {
case BC_CC: CE_ReplaceOPC (L[4], OP65_JPL); break;
case BC_CS: CE_ReplaceOPC (L[4], OP65_JMI); break;
default: Internal ("Unknown branch condition in OptCmp9");
}
/* Delete the asl insn */
CS_DelEntry (S, I+3);
/* Next sequence is somewhat ahead (if any) */
I += 3;
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
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 OptShift6 (CodeSeg* S)
/* Inline the shift subroutines. */
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
unsigned Shift;
unsigned Count;
CodeEntry* X;
unsigned IP;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for a call to one of the shift routine */
if (E->OPC == OP65_JSR &&
(Shift = GetShift (E->Arg)) != SHIFT_NONE &&
SHIFT_DIR (Shift) == SHIFT_DIR_LEFT &&
(Count = SHIFT_COUNT (Shift)) > 0) {
/* Code is:
*
* stx tmp1
* asl a
* rol tmp1
* (repeat ShiftCount-1 times)
* ldx tmp1
*
* which makes 4 + 3 * ShiftCount bytes, compared to the original
* 3 bytes for the subroutine call. However, in most cases, the
* final load of the X register gets merged with some other insn
* and replaces a txa, so for a shift count of 1, we get a factor
* of 200, which matches nicely the CodeSizeFactor enabled with -Oi
*/
if (Count > 1 || S->CodeSizeFactor > 200) {
unsigned Size = 4 + 3 * Count;
if ((Size * 100 / 3) > S->CodeSizeFactor) {
/* Not acceptable */
goto NextEntry;
}
}
/* Inline the code. Insertion point is behind the subroutine call */
IP = (I + 1);
/* stx tmp1 */
X = NewCodeEntry (OP65_STX, AM65_ZP, "tmp1", 0, E->LI);
CS_InsertEntry (S, X, IP++);
while (Count--) {
/* asl a */
X = NewCodeEntry (OP65_ASL, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, IP++);
/* rol tmp1 */
X = NewCodeEntry (OP65_ROL, AM65_ZP, "tmp1", 0, E->LI);
CS_InsertEntry (S, X, IP++);
}
/* ldx tmp1 */
X = NewCodeEntry (OP65_LDX, AM65_ZP, "tmp1", 0, E->LI);
CS_InsertEntry (S, X, IP++);
/* Remove the subroutine call */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
NextEntry:
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptShift4 (CodeSeg* S)
/* Calls to the asraxN or shraxN routines may get replaced by one or more lsr
* insns if the value of X is zero.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
unsigned Shift;
unsigned Count;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_JSR &&
(Shift = GetShift (E->Arg)) != SHIFT_NONE &&
SHIFT_DIR (Shift) == SHIFT_DIR_RIGHT &&
E->RI->In.RegX == 0) {
CodeEntry* X;
/* Shift count may be in Y */
Count = SHIFT_COUNT (Shift);
if (Count == SHIFT_COUNT_Y) {
CodeLabel* L;
if (S->CodeSizeFactor < 200) {
/* Not acceptable */
goto NextEntry;
}
/* Generate:
*
* L1: lsr a
* dey
* bpl L1
* rol a
*
* A negative shift count or one that is greater or equal than
* the bit width of the left operand (which is promoted to
* integer before the operation) causes undefined behaviour, so
* above transformation is safe.
*/
/* lsr a */
X = NewCodeEntry (OP65_LSR, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, I+1);
L = CS_GenLabel (S, X);
/* dey */
X = NewCodeEntry (OP65_DEY, AM65_IMP, 0, 0, E->LI);
CS_InsertEntry (S, X, I+2);
/* bpl L1 */
X = NewCodeEntry (OP65_BPL, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, X, I+3);
/* rol a */
X = NewCodeEntry (OP65_ROL, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, I+4);
} else {
/* Insert shift insns */
while (Count--) {
X = NewCodeEntry (OP65_LSR, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, I+1);
}
}
/* Delete the call to shrax */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
NextEntry:
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptStore3 (CodeSeg* S)
/* Search for a call to steaxysp. If the eax register is not used later, and
** the value is constant, just use the A register and store directly into the
** stack.
*/
{
unsigned I;
unsigned Changes = 0;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Get the input registers */
const RegInfo* RI = E->RI;
/* Check for the call */
if (CE_IsCallTo (E, "steaxysp") &&
RegValIsKnown (RI->In.RegA) &&
RegValIsKnown (RI->In.RegX) &&
RegValIsKnown (RI->In.RegY) &&
RegValIsKnown (RI->In.SRegLo) &&
RegValIsKnown (RI->In.SRegHi) &&
!RegEAXUsed (S, I+1)) {
/* Get the register values */
unsigned char A = (unsigned char) RI->In.RegA;
unsigned char X = (unsigned char) RI->In.RegX;
unsigned char Y = (unsigned char) RI->In.RegY;
unsigned char L = (unsigned char) RI->In.SRegLo;
unsigned char H = (unsigned char) RI->In.SRegHi;
/* Setup other variables */
unsigned Done = 0;
CodeEntry* N;
unsigned IP = I + 1; /* Insertion point */
/* Replace the store. We will not remove the loads, since this is
** too complex and will be done by other optimizer steps.
*/
N = NewCodeEntry (OP65_LDA, AM65_IMM, MakeHexArg (A), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x01;
/* Check if we can store one of the other bytes */
if (A == X && (Done & 0x02) == 0) {
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+1), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x02;
}
if (A == L && (Done & 0x04) == 0) {
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+2), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x04;
}
if (A == H && (Done & 0x08) == 0) {
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+3), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x08;
}
/* Store the second byte */
if ((Done & 0x02) == 0) {
N = NewCodeEntry (OP65_LDA, AM65_IMM, MakeHexArg (X), 0, E->LI);
CS_InsertEntry (S, N, IP++);
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+1), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x02;
}
/* Check if we can store one of the other bytes */
if (X == L && (Done & 0x04) == 0) {
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+2), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x04;
}
if (X == H && (Done & 0x08) == 0) {
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+3), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x08;
}
/* Store the third byte */
if ((Done & 0x04) == 0) {
N = NewCodeEntry (OP65_LDA, AM65_IMM, MakeHexArg (L), 0, E->LI);
CS_InsertEntry (S, N, IP++);
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+2), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x04;
}
/* Check if we can store one of the other bytes */
if (L == H && (Done & 0x08) == 0) {
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+3), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x08;
}
/* Store the fourth byte */
if ((Done & 0x08) == 0) {
N = NewCodeEntry (OP65_LDA, AM65_IMM, MakeHexArg (H), 0, E->LI);
CS_InsertEntry (S, N, IP++);
N = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (Y+3), 0, E->LI);
CS_InsertEntry (S, N, IP++);
InsertStore (S, &IP, E->LI);
Done |= 0x08;
}
/* Remove the call */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptBNegAX4 (CodeSeg* S)
/* Search for the sequence:
*
* jsr xxx
* jsr bnega(x)
* jeq/jne ...
*
* and replace it by:
*
* jsr xxx
* <boolean test>
* jne/jeq ...
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[2];
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for the sequence */
if (E->OPC == OP65_JSR &&
CS_GetEntries (S, L, I+1, 2) &&
L[0]->OPC == OP65_JSR &&
strncmp (L[0]->Arg,"bnega",5) == 0 &&
!CE_HasLabel (L[0]) &&
(L[1]->Info & OF_ZBRA) != 0 &&
!CE_HasLabel (L[1])) {
CodeEntry* X;
/* Check if we're calling bnega or bnegax */
int ByteSized = (strcmp (L[0]->Arg, "bnega") == 0);
/* Insert apropriate test code */
if (ByteSized) {
/* Test bytes */
X = NewCodeEntry (OP65_TAX, AM65_IMP, 0, 0, L[0]->LI);
CS_InsertEntry (S, X, I+2);
} else {
/* Test words */
X = NewCodeEntry (OP65_STX, AM65_ZP, "tmp1", 0, L[0]->LI);
CS_InsertEntry (S, X, I+2);
X = NewCodeEntry (OP65_ORA, AM65_ZP, "tmp1", 0, L[0]->LI);
CS_InsertEntry (S, X, I+3);
}
/* Delete the subroutine call */
CS_DelEntry (S, I+1);
/* Invert the branch */
CE_ReplaceOPC (L[1], GetInverseBranch (L[1]->OPC));
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp3 (CodeSeg* S)
/* Search for
*
* lda/and/ora/eor ...
* cmp #$00
* jeq/jne
* or
* lda/and/ora/eor ...
* cmp #$00
* jsr boolxx
*
* and remove the cmp.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[3];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if ((L[0]->OPC == OP65_ADC ||
L[0]->OPC == OP65_AND ||
L[0]->OPC == OP65_ASL ||
L[0]->OPC == OP65_DEA ||
L[0]->OPC == OP65_EOR ||
L[0]->OPC == OP65_INA ||
L[0]->OPC == OP65_LDA ||
L[0]->OPC == OP65_LSR ||
L[0]->OPC == OP65_ORA ||
L[0]->OPC == OP65_PLA ||
L[0]->OPC == OP65_SBC ||
L[0]->OPC == OP65_TXA ||
L[0]->OPC == OP65_TYA) &&
!CS_RangeHasLabel (S, I+1, 2) &&
CS_GetEntries (S, L+1, I+1, 2) &&
L[1]->OPC == OP65_CMP &&
CE_IsKnownImm (L[1], 0)) {
int Delete = 0;
/* Check for the call to boolxx. We only remove the compare if
* the carry flag is not evaluated later, because the load will
* not set the carry flag.
*/
if (L[2]->OPC == OP65_JSR) {
switch (FindBoolCmpCond (L[2]->Arg)) {
case CMP_EQ:
case CMP_NE:
case CMP_GT:
case CMP_GE:
case CMP_LT:
case CMP_LE:
/* Remove the compare */
Delete = 1;
break;
case CMP_UGT:
case CMP_UGE:
case CMP_ULT:
case CMP_ULE:
case CMP_INV:
/* Leave it alone */
break;
}
} else if ((L[2]->Info & OF_FBRA) != 0) {
/* The following insn branches on the condition of the load,
* so the compare instruction might be removed. For safety,
* do some more checks if the carry isn't used later, since
* the compare does set the carry, but the load does not.
*/
CodeEntry* E;
CodeEntry* N;
if ((E = CS_GetNextEntry (S, I+2)) != 0 &&
L[2]->JumpTo != 0 &&
(N = L[2]->JumpTo->Owner) != 0 &&
N->OPC != OP65_BCC &&
N->OPC != OP65_BCS &&
N->OPC != OP65_JCC &&
N->OPC != OP65_JCS &&
(N->OPC != OP65_JSR ||
FindBoolCmpCond (N->Arg) == CMP_INV)) {
/* The following insn branches on the condition of a load,
* and there's no use of the carry flag in sight, so the
* compare instruction can be removed.
*/
Delete = 1;
}
}
/* Delete the compare if we can */
if (Delete) {
CS_DelEntry (S, I+1);
++Changes;
}
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp8 (CodeSeg* S)
/* Check for register compares where the contents of the register and therefore
* the result of the compare is known.
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
int RegVal;
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check for a compare against an immediate value */
if ((E->Info & OF_CMP) != 0 &&
(RegVal = GetCmpRegVal (E)) >= 0 &&
CE_IsConstImm (E)) {
/* We are able to evaluate the compare at compile time. Check if
* one or more branches are ahead.
*/
unsigned JumpsChanged = 0;
CodeEntry* N;
while ((N = CS_GetNextEntry (S, I)) != 0 && /* Followed by something.. */
(N->Info & OF_CBRA) != 0 && /* ..that is a cond branch.. */
!CE_HasLabel (N)) { /* ..and has no label */
/* Evaluate the branch condition */
int Cond;
switch (GetBranchCond (N->OPC)) {
case BC_CC:
Cond = ((unsigned char)RegVal) < ((unsigned char)E->Num);
break;
case BC_CS:
Cond = ((unsigned char)RegVal) >= ((unsigned char)E->Num);
break;
case BC_EQ:
Cond = ((unsigned char)RegVal) == ((unsigned char)E->Num);
break;
case BC_MI:
Cond = ((signed char)RegVal) < ((signed char)E->Num);
break;
case BC_NE:
Cond = ((unsigned char)RegVal) != ((unsigned char)E->Num);
break;
case BC_PL:
Cond = ((signed char)RegVal) >= ((signed char)E->Num);
break;
case BC_VC:
case BC_VS:
/* Not set by the compare operation, bail out (Note:
* Just skipping anything here is rather stupid, but
* the sequence is never generated by the compiler,
* so it's quite safe to skip).
*/
goto NextEntry;
default:
Internal ("Unknown branch condition");
}
/* If the condition is false, we may remove the jump. Otherwise
* the branch will always be taken, so we may replace it by a
* jump (and bail out).
*/
if (!Cond) {
CS_DelEntry (S, I+1);
} else {
CodeLabel* L = N->JumpTo;
const char* LabelName = L? L->Name : N->Arg;
CodeEntry* X = NewCodeEntry (OP65_JMP, AM65_BRA, LabelName, L, N->LI);
CS_InsertEntry (S, X, I+2);
CS_DelEntry (S, I+1);
}
/* Remember, we had changes */
++JumpsChanged;
++Changes;
}
/* If we have made changes above, we may also remove the compare */
if (JumpsChanged) {
CS_DelEntry (S, I);
}
}
NextEntry:
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptStore5 (CodeSeg* S)
/* Search for the sequence
**
** lda foo
** ldx bar
** sta something
** stx something-else
**
** and replace it by
**
** lda foo
** sta something
** lda bar
** sta something-else
**
** if X is not used later. This replacement doesn't save any cycles or bytes,
** but it keeps the value of X, which may be reused later.
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[4];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if (L[0]->OPC == OP65_LDA &&
!CS_RangeHasLabel (S, I+1, 3) &&
CS_GetEntries (S, L+1, I+1, 3) &&
L[1]->OPC == OP65_LDX &&
L[2]->OPC == OP65_STA &&
L[3]->OPC == OP65_STX &&
!RegXUsed (S, I+4)) {
CodeEntry* X;
/* Insert the code after the sequence */
X = NewCodeEntry (OP65_LDA, L[1]->AM, L[1]->Arg, 0, L[1]->LI);
CS_InsertEntry (S, X, I+4);
X = NewCodeEntry (OP65_STA, L[3]->AM, L[3]->Arg, 0, L[3]->LI);
CS_InsertEntry (S, X, I+5);
/* Delete the old code */
CS_DelEntry (S, I+3);
CS_DelEntry (S, I+1);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptCmp5 (CodeSeg* S)
/* Optimize compares of local variables:
*
* ldy #o
* jsr ldaxysp
* cpx #a
* bne L1
* cmp #b
* jne/jeq L2
*/
{
unsigned Changes = 0;
/* Walk over the entries */
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[6];
/* Get the next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if (L[0]->OPC == OP65_LDY &&
CE_IsConstImm (L[0]) &&
CS_GetEntries (S, L+1, I+1, 5) &&
!CE_HasLabel (L[1]) &&
CE_IsCallTo (L[1], "ldaxysp") &&
IsImmCmp16 (L+2)) {
if ((L[5]->Info & OF_FBRA) != 0 && L[2]->Num == 0 && L[4]->Num == 0) {
CodeEntry* X;
char Buf[20];
/* The value is zero, we may use the simple code version:
* ldy #o-1
* lda (sp),y
* ldy #o
* ora (sp),y
* jne/jeq ...
*/
sprintf (Buf, "$%02X", (int)(L[0]->Num-1));
X = NewCodeEntry (OP65_LDY, AM65_IMM, Buf, 0, L[0]->LI);
CS_InsertEntry (S, X, I+1);
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
CS_InsertEntry (S, X, I+2);
X = NewCodeEntry (OP65_LDY, AM65_IMM, L[0]->Arg, 0, L[0]->LI);
CS_InsertEntry (S, X, I+3);
X = NewCodeEntry (OP65_ORA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
CS_InsertEntry (S, X, I+4);
CS_DelEntries (S, I+5, 3); /* cpx/bne/cmp */
CS_DelEntry (S, I); /* ldy */
} else {
CodeEntry* X;
char Buf[20];
/* Change the code to just use the A register. Move the load
* of the low byte after the first branch if possible:
*
* ldy #o
* lda (sp),y
* cmp #a
* bne L1
* ldy #o-1
* lda (sp),y
* cmp #b
* jne/jeq ...
*/
X = NewCodeEntry (OP65_LDY, AM65_IMM, L[0]->Arg, 0, L[0]->LI);
CS_InsertEntry (S, X, I+3);
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
CS_InsertEntry (S, X, I+4);
X = NewCodeEntry (OP65_CMP, L[2]->AM, L[2]->Arg, 0, L[2]->LI);
CS_InsertEntry (S, X, I+5);
sprintf (Buf, "$%02X", (int)(L[0]->Num-1));
X = NewCodeEntry (OP65_LDY, AM65_IMM, Buf, 0, L[0]->LI);
CS_InsertEntry (S, X, I+7);
X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
CS_InsertEntry (S, X, I+8);
CS_DelEntries (S, I, 3); /* ldy/jsr/cpx */
}
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}