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Refactor: remove StackOpData side effects from IsRegVar() and PreCondOk()/RegAPreCondOk(); setting StackOpData.ZPLo/ZPHi is explicit.

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This commit is contained in:
Alex Volkov
2026-03-10 19:23:40 -04:00
parent 1b778edee8
commit 505698c450
3 changed files with 125 additions and 47 deletions
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22
src/cc65/codeoptutil.c
View File

@@ -756,6 +756,10 @@ void ResetStackOpData (StackOpData* Data)
Data->PushIndex = -1;
Data->OpIndex = -1;
/* Clear to prevent silent optimizer bugs */
Data->ZPLo = 0;
Data->ZPHi = 0;
}
@@ -946,10 +950,9 @@ void AdjustStackOffset (StackOpData* D, unsigned Offs)
int IsRegVar (StackOpData* D)
int IsRegVar (const StackOpData* D)
/* If the value pushed is that of a zeropage variable that is unchanged until Op,
** replace ZPLo and ZPHi in the given StackOpData struct by the variable and return true.
** Otherwise leave D untouched and return false.
** return true.
*/
{
CodeEntry* LoadA = D->Lhs.A.LoadEntry;
@@ -979,9 +982,7 @@ int IsRegVar (StackOpData* D)
return 0;
}
/* Use the zero page location directly */
D->ZPLo = LoadA->Arg;
D->ZPHi = LoadX->Arg;
/* ZP location can be used directly */
return 1;
}
@@ -990,6 +991,8 @@ int IsRegVar (StackOpData* D)
void AddStoreLhsA (StackOpData* D)
/* Add a store to zero page after the push insn */
{
CHECK (D->ZPLo != 0);
CodeEntry* X = NewCodeEntry (OP65_STA, AM65_ZP, D->ZPLo, 0, D->PushEntry->LI);
InsertEntry (D, X, D->PushIndex+1);
}
@@ -999,6 +1002,8 @@ void AddStoreLhsA (StackOpData* D)
void AddStoreLhsX (StackOpData* D)
/* Add a store to zero page after the push insn */
{
CHECK (D->ZPHi != 0);
CodeEntry* X = NewCodeEntry (OP65_STX, AM65_ZP, D->ZPHi, 0, D->PushEntry->LI);
InsertEntry (D, X, D->PushIndex+1);
}
@@ -1071,6 +1076,8 @@ void AddOpLow (StackOpData* D, opc_t OPC, LoadInfo* LI)
} else {
CHECK (D->ZPLo != 0);
/* Op with temp storage */
X = NewCodeEntry (OPC, AM65_ZP, D->ZPLo, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
@@ -1134,6 +1141,9 @@ void AddOpHigh (StackOpData* D, opc_t OPC, LoadInfo* LI, int KeepResult)
}
} else {
CHECK (D->ZPHi != 0);
/* opc zphi */
X = NewCodeEntry (OPC, AM65_ZP, D->ZPHi, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);

5
src/cc65/codeoptutil.h
View File

@@ -223,10 +223,9 @@ void AdjustStackOffset (StackOpData* D, unsigned Offs);
** OpIndex is adjusted according to the insertions.
*/
int IsRegVar (StackOpData* D);
int IsRegVar (const StackOpData* D);
/* If the value pushed is that of a zeropage variable that is unchanged until Op,
** replace ZPLo and ZPHi in the given StackOpData struct by the variable and return true.
** Otherwise leave D untouched and return false.
** return true.
*/
void AddStoreLhsA (StackOpData* D);

145
src/cc65/coptstop.c
View File

@@ -160,6 +160,58 @@ static int SameRegXValue (StackOpData* D)
static void UseLhsRegVarLoc (StackOpData* D)
/* Prepare StackOpData to use the Lhs ZP location. */
{
/* Trying to use a non-ZP var is fatal here. */
CHECK (IsRegVar (D));
/* Use the ZP location directly from Lhs */
D->ZPLo = D->Lhs.A.LoadEntry->Arg;
D->ZPHi = D->Lhs.X.LoadEntry->Arg;
}
static int HaveUnusedTempZPLoc (const StackOpData* D)
/* Determine if an unused temp ZP location is available. */
{
/* We've tracked the used ZP locations; see if any are unused.
** Note: they must be checked as LO+HI pairs individually.
** This must match the conditions used in ChooseTempZPLoc() exactly,
** but it is a lesser evil than predicate side effects.
*/
return (D->ZPUsage & REG_PTR1) == 0 || (D->ZPUsage & REG_SREG) == 0 ||
(D->ZPUsage & REG_PTR2) == 0;
}
static void ChooseTempZPLoc (StackOpData* D)
/* Determine the temp ZP location to use from ZP usage flags.
** Note: one not being available is a fatal condition here.
*/
{
/* Determine the zero page locations to use. We've tracked the used
** ZP locations, so try to find some for us that are unused.
*/
if ((D->ZPUsage & REG_PTR1) == 0) {
D->ZPLo = "ptr1";
D->ZPHi = "ptr1+1";
} else if ((D->ZPUsage & REG_SREG) == 0) {
D->ZPLo = "sreg";
D->ZPHi = "sreg+1";
} else if ((D->ZPUsage & REG_PTR2) == 0) {
D->ZPLo = "ptr2";
D->ZPHi = "ptr2+1";
} else {
/* No registers available */
Internal ("No temp ZP locations available. Was pre-check peformed?");
}
}
/*****************************************************************************/
/* Actual optimization functions */
/*****************************************************************************/
@@ -249,6 +301,10 @@ static unsigned Opt_toseqax_tosneax (StackOpData* D, const char* BoolTransformer
} else {
/* Implement the op via a temp ZP location */
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Save lhs into zeropage, then compare */
AddStoreLhsX (D);
AddStoreLhsA (D);
@@ -313,6 +369,10 @@ static unsigned Opt_tosshift (StackOpData* D, const char* Name)
} else {
/* Implement the op via a temp ZP location */
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Save lhs into zeropage and reload later */
AddStoreLhsX (D);
AddStoreLhsA (D);
@@ -357,10 +417,13 @@ static unsigned Opt___bzero (StackOpData* D)
CodeLabel* L;
/* Check if we're using a register variable */
/* ### Caution: IsRegVar() has deterministic side effects over StackOpData,
** overriding the ZP location set by PreCondOk().
*/
if (!IsRegVar (D)) {
if (IsRegVar (D)) {
/* Can use the Lhs ZP var directly here */
UseLhsRegVarLoc (D);
} else {
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store the value into the zeropage instead of pushing it */
AddStoreLhsX (D);
AddStoreLhsA (D);
@@ -452,10 +515,13 @@ static unsigned Opt_staspidx (StackOpData* D)
CodeEntry* X;
/* Check if we're using a register variable */
/* ### Caution: IsRegVar() has deterministic side effects over StackOpData,
** overriding the ZP location set by PreCondOk().
*/
if (!IsRegVar (D)) {
if (IsRegVar (D)) {
/* Can use the Lhs ZP var directly here */
UseLhsRegVarLoc (D);
} else {
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store the value into the zeropage instead of pushing it */
AddStoreLhsX (D);
AddStoreLhsA (D);
@@ -481,10 +547,13 @@ static unsigned Opt_staxspidx (StackOpData* D)
const char* Arg = 0;
/* Check if we're using a register variable */
/* ### Caution: IsRegVar() has deterministic side effects over StackOpData,
** overriding the ZP location set by PreCondOk().
*/
if (!IsRegVar (D)) {
if (IsRegVar (D)) {
/* Can use the Lhs ZP var directly here */
UseLhsRegVarLoc (D);
} else {
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store the value into the zeropage instead of pushing it */
AddStoreLhsX (D);
AddStoreLhsA (D);
@@ -564,6 +633,9 @@ static unsigned Opt_tosaddax (StackOpData* D)
/* We need the entry behind the add */
CHECK (D->NextEntry != 0);
/* Because of HaveUnusedTempZPLoc precondition in all cases */
ChooseTempZPLoc (D);
/* Check if the X register is known and zero when the add is done, and
** if the add is followed by
**
@@ -698,6 +770,9 @@ static unsigned Opt_tosaddax (StackOpData* D)
static unsigned Opt_tosandax (StackOpData* D)
/* Optimize the tosandax sequence */
{
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store the value into the zeropage instead of pushing it */
ReplacePushByStore (D);
@@ -867,6 +942,9 @@ static unsigned Opt_tosneax (StackOpData* D)
static unsigned Opt_tosorax (StackOpData* D)
/* Optimize the tosorax sequence */
{
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store the value into the zeropage instead of pushing it */
ReplacePushByStore (D);
@@ -1114,6 +1192,8 @@ static unsigned Opt_tosxorax (StackOpData* D)
{
CodeEntry* X;
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store the value into the zeropage instead of pushing it */
ReplacePushByStore (D);
@@ -1168,9 +1248,14 @@ static unsigned Opt_a_tosbitwise (StackOpData* D, opc_t OPC)
X = NewCodeEntry (OPC, D->Lhs.A.LoadEntry->AM, D->Lhs.A.LoadEntry->Arg, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
} else {
/* Implement the op via a temp ZP location */
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Backup lhs */
X = NewCodeEntry (OP65_STA, AM65_ZP, D->ZPLo, 0, D->PushEntry->LI);
InsertEntry (D, X, D->PushIndex+1);
/* Add code for low operand */
X = NewCodeEntry (OPC, AM65_ZP, D->ZPLo, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
@@ -1261,6 +1346,9 @@ static unsigned Opt_a_toscmpbool (StackOpData* D, const char* BoolTransformer)
/* This shouldn't fail */
CHECK (BoolTransformer);
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Save lhs into zeropage */
AddStoreLhsA (D);
/* AddStoreLhsA may have moved the OpIndex, recalculate insertion point to prevent label migration. */
@@ -1319,6 +1407,9 @@ static unsigned Opt_a_tosicmp (StackOpData* D)
/* Because of SameRegAValue */
CHECK (D->Rhs.A.ChgIndex >= 0);
/* HaveUnusedTempZPLoc precondition must have been met */
ChooseTempZPLoc (D);
/* Store LHS in ZP and reload it before op */
X = NewCodeEntry (OP65_STA, AM65_ZP, D->ZPLo, 0, D->PushEntry->LI);
InsertEntry (D, X, D->PushIndex + 1);
@@ -1729,19 +1820,8 @@ static int PreCondOk (StackOpData* D)
return 0;
}
/* Determine the zero page locations to use. We've tracked the used
** ZP locations, so try to find some for us that are unused.
*/
if ((D->ZPUsage & REG_PTR1) == REG_NONE) {
D->ZPLo = "ptr1";
D->ZPHi = "ptr1+1";
} else if ((D->ZPUsage & REG_SREG) == REG_NONE) {
D->ZPLo = "sreg";
D->ZPHi = "sreg+1";
} else if ((D->ZPUsage & REG_PTR2) == REG_NONE) {
D->ZPLo = "ptr2";
D->ZPHi = "ptr2+1";
} else {
/* Check if an unused temp ZP location is available */
if (!HaveUnusedTempZPLoc (D)) {
/* No registers available */
return 0;
}
@@ -1884,19 +1964,8 @@ static int RegAPreCondOk (StackOpData* D)
return 0;
}
/* Determine the zero page locations to use. We've tracked the used
** ZP locations, so try to find some for us that are unused.
*/
if ((D->ZPUsage & REG_PTR1) == REG_NONE) {
D->ZPLo = "ptr1";
D->ZPHi = "ptr1+1";
} else if ((D->ZPUsage & REG_SREG) == REG_NONE) {
D->ZPLo = "sreg";
D->ZPHi = "sreg+1";
} else if ((D->ZPUsage & REG_PTR2) == REG_NONE) {
D->ZPLo = "ptr2";
D->ZPHi = "ptr2+1";
} else {
/* Check if an unused temp ZP location is available */
if (!HaveUnusedTempZPLoc (D)) {
/* No registers available */
return 0;
}