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;
}
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 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;
}
void CS_GenRegInfo (CodeSeg* S)
/* Generate register infos for all instructions */
{
unsigned I;
RegContents Regs; /* Initial register contents */
RegContents* CurrentRegs; /* Current register contents */
int WasJump; /* True if last insn was a jump */
int Done; /* All runs done flag */
/* Be sure to delete all register infos */
CS_FreeRegInfo (S);
/* We may need two runs to get back references right */
do {
/* Assume we're done after this run */
Done = 1;
/* On entry, the register contents are unknown */
RC_Invalidate (&Regs);
CurrentRegs = &Regs;
/* Walk over all insns and note just the changes from one insn to the
* next one.
*/
WasJump = 0;
for (I = 0; I < CS_GetEntryCount (S); ++I) {
CodeEntry* P;
/* Get the next instruction */
CodeEntry* E = CollAtUnchecked (&S->Entries, I);
/* If the instruction has a label, we need some special handling */
unsigned LabelCount = CE_GetLabelCount (E);
if (LabelCount > 0) {
/* Loop over all entry points that jump here. If these entry
* points already have register info, check if all values are
* known and identical. If all values are identical, and the
* preceeding instruction was not an unconditional branch, check
* if the register value on exit of the preceeding instruction
* is also identical. If all these values are identical, the
* value of a register is known, otherwise it is unknown.
*/
CodeLabel* Label = CE_GetLabel (E, 0);
unsigned Entry;
if (WasJump) {
/* Preceeding insn was an unconditional branch */
CodeEntry* J = CL_GetRef(Label, 0);
if (J->RI) {
Regs = J->RI->Out2;
} else {
RC_Invalidate (&Regs);
}
Entry = 1;
} else {
Regs = *CurrentRegs;
Entry = 0;
}
while (Entry < CL_GetRefCount (Label)) {
/* Get this entry */
CodeEntry* J = CL_GetRef (Label, Entry);
if (J->RI == 0) {
/* No register info for this entry. This means that the
* instruction that jumps here is at higher addresses and
* the jump is a backward jump. We need a second run to
* get the register info right in this case. Until then,
* assume unknown register contents.
*/
Done = 0;
RC_Invalidate (&Regs);
break;
}
if (J->RI->Out2.RegA != Regs.RegA) {
Regs.RegA = UNKNOWN_REGVAL;
}
if (J->RI->Out2.RegX != Regs.RegX) {
Regs.RegX = UNKNOWN_REGVAL;
}
if (J->RI->Out2.RegY != Regs.RegY) {
Regs.RegY = UNKNOWN_REGVAL;
}
if (J->RI->Out2.SRegLo != Regs.SRegLo) {
Regs.SRegLo = UNKNOWN_REGVAL;
}
if (J->RI->Out2.SRegHi != Regs.SRegHi) {
Regs.SRegHi = UNKNOWN_REGVAL;
}
if (J->RI->Out2.Tmp1 != Regs.Tmp1) {
Regs.Tmp1 = UNKNOWN_REGVAL;
}
++Entry;
}
/* Use this register info */
CurrentRegs = &Regs;
}
/* Generate register info for this instruction */
CE_GenRegInfo (E, CurrentRegs);
/* Remember for the next insn if this insn was an uncondition branch */
WasJump = (E->Info & OF_UBRA) != 0;
/* Output registers for this insn are input for the next */
CurrentRegs = &E->RI->Out;
/* If this insn is a branch on zero flag, we may have more info on
* register contents for one of both flow directions, but only if
* there is a previous instruction.
*/
if ((E->Info & OF_ZBRA) != 0 && (P = CS_GetPrevEntry (S, I)) != 0) {
/* Get the branch condition */
bc_t BC = GetBranchCond (E->OPC);
/* Check the previous instruction */
switch (P->OPC) {
case OP65_ADC:
case OP65_AND:
case OP65_DEA:
case OP65_EOR:
case OP65_INA:
case OP65_LDA:
case OP65_ORA:
case OP65_PLA:
case OP65_SBC:
/* A is zero in one execution flow direction */
if (BC == BC_EQ) {
E->RI->Out2.RegA = 0;
} else {
E->RI->Out.RegA = 0;
}
break;
case OP65_CMP:
/* If this is an immidiate compare, the A register has
* the value of the compare later.
*/
if (CE_IsConstImm (P)) {
if (BC == BC_EQ) {
E->RI->Out2.RegA = (unsigned char)P->Num;
} else {
E->RI->Out.RegA = (unsigned char)P->Num;
}
}
break;
case OP65_CPX:
/* If this is an immidiate compare, the X register has
* the value of the compare later.
*/
if (CE_IsConstImm (P)) {
if (BC == BC_EQ) {
E->RI->Out2.RegX = (unsigned char)P->Num;
} else {
E->RI->Out.RegX = (unsigned char)P->Num;
}
}
break;
case OP65_CPY:
/* If this is an immidiate compare, the Y register has
* the value of the compare later.
*/
if (CE_IsConstImm (P)) {
if (BC == BC_EQ) {
E->RI->Out2.RegY = (unsigned char)P->Num;
} else {
E->RI->Out.RegY = (unsigned char)P->Num;
}
}
break;
case OP65_DEX:
case OP65_INX:
case OP65_LDX:
case OP65_PLX:
/* X is zero in one execution flow direction */
if (BC == BC_EQ) {
E->RI->Out2.RegX = 0;
} else {
E->RI->Out.RegX = 0;
}
break;
case OP65_DEY:
case OP65_INY:
case OP65_LDY:
case OP65_PLY:
/* X is zero in one execution flow direction */
if (BC == BC_EQ) {
E->RI->Out2.RegY = 0;
} else {
E->RI->Out.RegY = 0;
}
break;
case OP65_TAX:
case OP65_TXA:
/* If the branch is a beq, both A and X are zero at the
* branch target, otherwise they are zero at the next
* insn.
*/
if (BC == BC_EQ) {
E->RI->Out2.RegA = E->RI->Out2.RegX = 0;
} else {
E->RI->Out.RegA = E->RI->Out.RegX = 0;
}
break;
case OP65_TAY:
case OP65_TYA:
/* If the branch is a beq, both A and Y are zero at the
* branch target, otherwise they are zero at the next
* insn.
*/
if (BC == BC_EQ) {
E->RI->Out2.RegA = E->RI->Out2.RegY = 0;
} else {
E->RI->Out.RegA = E->RI->Out.RegY = 0;
}
break;
default:
break;
}
}
}
} while (!Done);
}
