unsigned OptPush2 (CodeSeg* S)
/* A sequence
*
* jsr ldaxidx
* jsr pushax
*
* may get replaced by
*
* jsr pushwidx
*
*/
{
unsigned I;
unsigned Changes = 0;
/* Generate register info */
CS_GenRegInfo (S);
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[2];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if (CE_IsCallTo (L[0], "ldaxidx") &&
(L[1] = CS_GetNextEntry (S, I)) != 0 &&
!CE_HasLabel (L[1]) &&
CE_IsCallTo (L[1], "pushax")) {
/* Insert new code behind the pushax */
CodeEntry* X;
/* jsr pushwidx */
X = NewCodeEntry (OP65_JSR, AM65_ABS, "pushwidx", 0, L[1]->LI);
CS_InsertEntry (S, X, I+2);
/* Delete the old code */
CS_DelEntries (S, I, 2);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Free the register info */
CS_FreeRegInfo (S);
/* 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 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;
}
static unsigned OptStackPtrOps (CodeSeg* S)
/* Merge adjacent calls to decsp into one. NOTE: This function won't merge all
** known cases!
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
unsigned Dec1;
unsigned Dec2;
const CodeEntry* N;
/* Get the next entry */
const CodeEntry* E = CS_GetEntry (S, I);
/* Check for decspn or subysp */
if (E->OPC == OP65_JSR &&
(Dec1 = IsDecSP (E)) > 0 &&
(N = CS_GetNextEntry (S, I)) != 0 &&
(Dec2 = IsDecSP (N)) > 0 &&
(Dec1 += Dec2) <= 255 &&
!CE_HasLabel (N)) {
CodeEntry* X;
char Buf[20];
/* We can combine the two */
if (Dec1 <= 8) {
/* Insert a call to decsp */
xsprintf (Buf, sizeof (Buf), "decsp%u", Dec1);
X = NewCodeEntry (OP65_JSR, AM65_ABS, Buf, 0, N->LI);
CS_InsertEntry (S, X, I+2);
} else {
/* Insert a call to subysp */
const char* Arg = MakeHexArg (Dec1);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, N->LI);
CS_InsertEntry (S, X, I+2);
X = NewCodeEntry (OP65_JSR, AM65_ABS, "subysp", 0, N->LI);
CS_InsertEntry (S, X, I+3);
}
/* Delete the old code */
CS_DelEntries (S, I, 2);
/* Regenerate register info */
CS_GenRegInfo (S);
/* Remember we had changes */
++Changes;
} else {
/* 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 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;
}
static void ReplaceCmp (CodeSeg* S, unsigned I, cmp_t Cond)
/* Helper function for the replacement of routines that return a boolean
* followed by a conditional jump. Instead of the boolean value, the condition
* codes are evaluated directly.
* I is the index of the conditional branch, the sequence is already checked
* to be correct.
*/
{
CodeEntry* N;
CodeLabel* L;
/* Get the entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Replace the conditional branch */
switch (Cond) {
case CMP_EQ:
CE_ReplaceOPC (E, OP65_JEQ);
break;
case CMP_NE:
CE_ReplaceOPC (E, OP65_JNE);
break;
case CMP_GT:
/* Replace by
* beq @L
* jpl Target
* @L: ...
*/
if ((N = CS_GetNextEntry (S, I)) == 0) {
/* No such entry */
Internal ("Invalid program flow");
}
L = CS_GenLabel (S, N);
N = NewCodeEntry (OP65_BEQ, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, N, I);
CE_ReplaceOPC (E, OP65_JPL);
break;
case CMP_GE:
CE_ReplaceOPC (E, OP65_JPL);
break;
case CMP_LT:
CE_ReplaceOPC (E, OP65_JMI);
break;
case CMP_LE:
/* Replace by
* jmi Target
* jeq Target
*/
CE_ReplaceOPC (E, OP65_JMI);
L = E->JumpTo;
N = NewCodeEntry (OP65_JEQ, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, N, I+1);
break;
case CMP_UGT:
/* Replace by
* beq @L
* jcs Target
* @L: ...
*/
if ((N = CS_GetNextEntry (S, I)) == 0) {
/* No such entry */
Internal ("Invalid program flow");
}
L = CS_GenLabel (S, N);
N = NewCodeEntry (OP65_BEQ, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, N, I);
CE_ReplaceOPC (E, OP65_JCS);
break;
case CMP_UGE:
CE_ReplaceOPC (E, OP65_JCS);
break;
case CMP_ULT:
CE_ReplaceOPC (E, OP65_JCC);
break;
case CMP_ULE:
/* Replace by
* jcc Target
* jeq Target
*/
CE_ReplaceOPC (E, OP65_JCC);
L = E->JumpTo;
N = NewCodeEntry (OP65_JEQ, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, N, I+1);
break;
default:
Internal ("Unknown jump condition: %d", Cond);
}
}
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 OptPush1 (CodeSeg* S)
/* Given a sequence
*
* jsr ldaxysp
* jsr pushax
*
* If a/x are not used later, and Y is known, replace that by
*
* ldy #xx+2
* jsr pushwysp
*
* saving 3 bytes and several cycles.
*/
{
unsigned I;
unsigned Changes = 0;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
CodeEntry* L[2];
/* Get next entry */
L[0] = CS_GetEntry (S, I);
/* Check for the sequence */
if (CE_IsCallTo (L[0], "ldaxysp") &&
RegValIsKnown (L[0]->RI->In.RegY) &&
L[0]->RI->In.RegY < 0xFE &&
(L[1] = CS_GetNextEntry (S, I)) != 0 &&
!CE_HasLabel (L[1]) &&
CE_IsCallTo (L[1], "pushax") &&
!RegAXUsed (S, I+2)) {
/* Insert new code behind the pushax */
const char* Arg;
CodeEntry* X;
/* ldy #xx+1 */
Arg = MakeHexArg (L[0]->RI->In.RegY+2);
X = NewCodeEntry (OP65_LDY, AM65_IMM, Arg, 0, L[0]->LI);
CS_InsertEntry (S, X, I+2);
/* jsr pushwysp */
X = NewCodeEntry (OP65_JSR, AM65_ABS, "pushwysp", 0, L[1]->LI);
CS_InsertEntry (S, X, I+3);
/* Delete the old code */
CS_DelEntries (S, I, 2);
/* Remember, we had changes */
++Changes;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
void CS_DelCodeRange (CodeSeg* S, unsigned First, unsigned Last)
/* Delete all entries between first and last, both inclusive. The function
* can only handle basic blocks (First is the only entry, Last the only exit)
* and no open labels. It will call FAIL if any of these preconditions are
* violated.
*/
{
unsigned I;
CodeEntry* FirstEntry;
/* Do some sanity checks */
CHECK (First <= Last && Last < CS_GetEntryCount (S));
/* If Last is actually the last insn, call CS_DelCodeAfter instead, which
* is more flexible in this case.
*/
if (Last == CS_GetEntryCount (S) - 1) {
CS_DelCodeAfter (S, First);
return;
}
/* Get the first entry and check if it has any labels. If it has, move
* them to the insn following Last. If Last is the last insn of the code
* segment, make them ownerless and move them to the label pool.
*/
FirstEntry = CS_GetEntry (S, First);
if (CE_HasLabel (FirstEntry)) {
/* Get the entry following last */
CodeEntry* FollowingEntry = CS_GetNextEntry (S, Last);
if (FollowingEntry) {
/* There is an entry after Last - move the labels */
CS_MoveLabels (S, FirstEntry, FollowingEntry);
} else {
/* Move the labels to the pool and clear the owner pointer */
CS_MoveLabelsToPool (S, FirstEntry);
}
}
/* First pass: Delete all references to labels. If the reference count
* for a label drops to zero, delete it.
*/
for (I = Last; I >= First; --I) {
/* Get the next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check if this entry has a label reference */
if (E->JumpTo) {
/* If the label is a label in the label pool, this is an error */
CodeLabel* L = E->JumpTo;
CHECK (CollIndex (&S->Labels, L) < 0);
/* Remove the reference to the label */
CS_RemoveLabelRef (S, E);
}
}
/* Second pass: Delete the instructions. If a label attached to an
* instruction still has references, it must be references from outside
* the deleted area, which is an error.
*/
for (I = Last; I >= First; --I) {
/* Get the next entry */
CodeEntry* E = CS_GetEntry (S, I);
/* Check if this entry has a label attached */
CHECK (!CE_HasLabel (E));
/* Delete the pointer to the entry */
CollDelete (&S->Entries, I);
/* Delete the entry itself */
FreeCodeEntry (E);
}
}
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 OptShift1 (CodeSeg* S)
/* A call to the shlaxN routine may get replaced by one or more asl insns
* if the value of X is not used later. If X is used later, but it is zero
* on entry and it's a shift by one, it may get replaced by:
*
* asl a
* bcc L1
* inx
* L1:
*
*/
{
unsigned Changes = 0;
unsigned I;
/* Walk over the entries */
I = 0;
while (I < CS_GetEntryCount (S)) {
unsigned Shift;
CodeEntry* N;
CodeEntry* X;
CodeLabel* L;
/* 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_LEFT) {
unsigned Count = SHIFT_COUNT (Shift);
if (!RegXUsed (S, I+1)) {
if (Count == SHIFT_COUNT_Y) {
CodeLabel* L;
if (S->CodeSizeFactor < 200) {
goto NextEntry;
}
/* Change into
*
* L1: asl a
* dey
* bpl L1
* ror a
*/
/* asl a */
X = NewCodeEntry (OP65_ASL, 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);
/* ror a */
X = NewCodeEntry (OP65_ROR, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, I+4);
} else {
/* Insert shift insns */
while (Count--) {
X = NewCodeEntry (OP65_ASL, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, I+1);
}
}
} else if (E->RI->In.RegX == 0 &&
Count == 1 &&
(N = CS_GetNextEntry (S, I)) != 0) {
/* asl a */
X = NewCodeEntry (OP65_ASL, AM65_ACC, "a", 0, E->LI);
CS_InsertEntry (S, X, I+1);
/* bcc L1 */
L = CS_GenLabel (S, N);
X = NewCodeEntry (OP65_BCC, AM65_BRA, L->Name, L, E->LI);
CS_InsertEntry (S, X, I+2);
/* inx */
X = NewCodeEntry (OP65_INX, AM65_IMP, 0, 0, E->LI);
CS_InsertEntry (S, X, I+3);
} else {
/* We won't handle this one */
goto NextEntry;
}
/* Delete the call to shlax */
CS_DelEntry (S, I);
/* Remember, we had changes */
++Changes;
}
NextEntry:
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}