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BUGFIX: Fix the "same X value" and "same A value" evaluations issue in OptStackOps(), where the values compared come from the wrong instruction when a runtime call has an asm label.

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This commit is contained in:
Alex Volkov
2026-03-10 20:08:35 -04:00
parent 505698c450
commit bf5d8c44e4
1 changed files with 23 additions and 65 deletions
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88
src/cc65/coptstop.c
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@@ -94,68 +94,34 @@ struct OptFuncDesc {
static int SameRegAValue (StackOpData* D)
/* Check if Rhs Reg A == Lhs Reg A */
static int SameRegAValueAtOp (const StackOpData* D, CodeEntry* OpEntry)
/* Check if Rhs Reg A at OpIndex == Lhs Reg A at PushIndex */
{
RegInfo* LRI = GetLastChangedRegInfo (D, &D->Lhs.A);
RegInfo* RRI = GetLastChangedRegInfo (D, &D->Rhs.A);
CodeEntry* PushEntry;
/* ### Bug: The Rhs Reg A value used in the logic here can be from a return
** value of the runtime call being optimized away (e.g. "jsr tosgtax"),
** and *not* its operand. That happens when the call insn (JSR) has a label.
** Then the RRI is that of the runtime call JSR, and the RRI->Out.RegA
** compares here are not valid.
** See OptStackOps(), case FoundPush: if (CE_HasLabel (E)) { ...
** and usage in Opt_a_tosicmp().
*/
/* RHS can have a -1 ChgIndex only if it is carried over from LHS */
if (RRI == 0 ||
(D->Rhs.A.ChgIndex >= 0 &&
D->Rhs.A.ChgIndex == D->Lhs.A.ChgIndex) ||
(LRI != 0 &&
RegValIsKnown (LRI->Out.RegA) &&
RegValIsKnown (RRI->Out.RegA) &&
(LRI->Out.RegA & 0xFF) == (RRI->Out.RegA & 0xFF))) {
return 1;
}
return 0;
CHECK (D->PushIndex >= 0);
PushEntry = CS_GetEntry (D->Code, D->PushIndex);
return
RegValIsKnown (PushEntry->RI->In.RegA) &&
RegValIsKnown (OpEntry->RI->In.RegA) &&
PushEntry->RI->In.RegA == OpEntry->RI->In.RegA;
}
static int SameRegXValue (StackOpData* D)
/* Check if Rhs Reg X == Lhs Reg X */
static int SameRegXValueAtOp (const StackOpData* D, CodeEntry* OpEntry)
/* Check if Rhs Reg X at OpIndex == Lhs Reg X at PushIndex */
{
RegInfo* LRI = GetLastChangedRegInfo (D, &D->Lhs.X);
RegInfo* RRI = GetLastChangedRegInfo (D, &D->Rhs.X);
CodeEntry* PushEntry;
/* ### Bug: The Rhs Reg X value used in the logic here can be from a return
** value of the runtime call being optimized away (e.g. "jsr tosgtax"),
** and *not* its operand. That happens when the call insn (JSR) has a label.
** Then the RRI is that of the runtime call JSR, and the RRI->Out.RegX
** compares here are not valid.
** See OptStackOps(), case FoundPush: if (CE_HasLabel (E)) { ...
** RegAPreCondOk() has special armour code for this issue:
** if (LhsHiVal != RhsHiVal) { /Cannot optimize/ break; }
*/
if (RRI == 0 ||
(D->Rhs.X.ChgIndex >= 0 &&
D->Rhs.X.ChgIndex == D->Lhs.X.ChgIndex) ||
(LRI != 0 &&
RegValIsKnown (LRI->Out.RegX) &&
RegValIsKnown (RRI->Out.RegX) &&
(LRI->Out.RegX & 0xFF) == (RRI->Out.RegX & 0xFF))) {
return 1;
}
return 0;
CHECK (D->PushIndex >= 0);
PushEntry = CS_GetEntry (D->Code, D->PushIndex);
return
RegValIsKnown (PushEntry->RI->In.RegX) &&
RegValIsKnown (OpEntry->RI->In.RegX) &&
PushEntry->RI->In.RegX == OpEntry->RI->In.RegX;
}
@@ -1251,11 +1217,11 @@ static unsigned Opt_a_tosbitwise (StackOpData* D, opc_t OPC)
/* 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++);
@@ -1398,13 +1364,8 @@ static unsigned Opt_a_tosicmp (StackOpData* D)
RegInfo* RI;
const char* Arg;
/* ### Bug to come: The Reg A value used in SameRegAValue() call here
** can be from the wrong instruction in some cases, producing invalid
** result. Any effects of this issue are currently suppressed because
** other subopts eliminate this subopt's use cases.
*/
if (!SameRegAValue (D)) {
/* Because of SameRegAValue */
if (!SameRegAValueAtOp (D, D->OpEntry)) {
/* Because of SameRegAValueAtOp */
CHECK (D->Rhs.A.ChgIndex >= 0);
/* HaveUnusedTempZPLoc precondition must have been met */
@@ -2079,9 +2040,6 @@ unsigned OptStackOps (CodeSeg* S)
** Treat this as a change to all regs.
*/
ClearLoadInfo (&Data.Rhs);
/* ### Note: this causes the below SameRegXValue() to not
** work correctly in some cases.
*/
Data.Rhs.A.ChgIndex = I;
Data.Rhs.X.ChgIndex = I;
Data.Rhs.Y.ChgIndex = I;
@@ -2096,7 +2054,7 @@ unsigned OptStackOps (CodeSeg* S)
** When the A-only preconditions fail, good A/X cases are
** left unoptimized.
*/
if (SameRegXValue (&Data)) {
if (SameRegXValueAtOp (&Data, E)) {
Data.OptFunc = FindFunc (FuncRegATable, FUNC_COUNT (FuncRegATable), E->Arg);
IsRegAOptFunc = 1;
}