bslathi19/cc65
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Annotations ahead of refactoring: bugs., looming bugs, and work notes.

Browse Source
This commit is contained in:
Alex Volkov
2026-03-10 17:46:40 -04:00
parent a29ce64fb5
commit 1b778edee8
1 changed files with 81 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

81
src/cc65/coptstop.c
View File

@@ -100,6 +100,15 @@ static int SameRegAValue (StackOpData* D)
RegInfo* LRI = GetLastChangedRegInfo (D, &D->Lhs.A);
RegInfo* RRI = GetLastChangedRegInfo (D, &D->Rhs.A);
/* ### 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 &&
@@ -124,6 +133,16 @@ static int SameRegXValue (StackOpData* D)
RegInfo* LRI = GetLastChangedRegInfo (D, &D->Lhs.X);
RegInfo* RRI = GetLastChangedRegInfo (D, &D->Rhs.X);
/* ### 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) ||
@@ -338,6 +357,9 @@ 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)) {
/* Store the value into the zeropage instead of pushing it */
AddStoreLhsX (D);
@@ -430,6 +452,9 @@ 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)) {
/* Store the value into the zeropage instead of pushing it */
AddStoreLhsX (D);
@@ -456,12 +481,20 @@ 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)) {
/* Store the value into the zeropage instead of pushing it */
AddStoreLhsX (D);
AddStoreLhsA (D);
}
/* Note: This subopt demands for REG_AX to not be used later.
** X is unchanged by the code here, so only REG_A must not be used.
** Note 2: Should be updated to common D->IP++ syntax.
*/
/* Inline the store */
/* sta (zp),y */
@@ -477,6 +510,10 @@ static unsigned Opt_staxspidx (StackOpData* D)
}
InsertEntry (D, X, D->OpIndex+2);
/* ### TODO: We could do a PHA here to save A if it is used, and remove
** the "A not used" precondition entirely.
*/
if (RegValIsKnown (D->OpEntry->RI->In.RegX)) {
/* Value of X is known */
Arg = MakeHexArg (D->OpEntry->RI->In.RegX);
@@ -487,6 +524,10 @@ static unsigned Opt_staxspidx (StackOpData* D)
}
InsertEntry (D, X, D->OpIndex+3);
/* ### TODO: We could do a PLA here to restore A if it is used, and remove
** the "A not used" precondition entirely.
*/
/* sta (zp),y */
X = NewCodeEntry (OP65_STA, AM65_ZP_INDY, D->ZPLo, 0, D->OpEntry->LI);
InsertEntry (D, X, D->OpIndex+4);
@@ -502,6 +543,9 @@ static unsigned Opt_staxspidx (StackOpData* D)
}
InsertEntry (D, X, D->OpIndex+5);
/* Note: We have not flagged any loads for removal. If any are unnecessary,
** other optimizers will remove them.
*/
/* Remove the push and the call to the staxspidx function */
RemoveRemainders (D);
@@ -1115,6 +1159,9 @@ static unsigned Opt_a_tosbitwise (StackOpData* D, opc_t OPC)
D->IP = D->OpIndex+1;
/* Backup lhs if necessary */
/* ### Note: This should be rearranged into a common form used in others:
** if (Rhs) { } else if (Lhs) { } else { ZP }.
*/
if ((D->Rhs.A.Flags & LI_DIRECT) == 0) {
if ((D->Lhs.A.Flags & (LI_DIRECT | LI_RELOAD_Y)) == LI_DIRECT) {
/* Just reload lhs */
@@ -1137,6 +1184,13 @@ static unsigned Opt_a_tosbitwise (StackOpData* D, opc_t OPC)
D->Rhs.A.Flags |= LI_REMOVE;
}
/* ### Bug to come: there are dangerous Rhs X removal attempts here.
** Runtime function calls can be "loads", and must be treated as a
** single A/X unit, so removal of X load alone is not valid.
** This can be solved with an additional "removable Rhs" test, or
** by simply not forcing the LI_REMOVE flag and letting other optimizers
** remove any unnecessary loads.
*/
/* Do high-byte operation only when its result is used */
if ((GetRegInfo (D->Code, D->IP, REG_X) & REG_X) != 0) {
/* Replace the high-byte load with 0 for EOR, or just leave it alone */
@@ -1256,6 +1310,11 @@ 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 */
CHECK (D->Rhs.A.ChgIndex >= 0);
@@ -1280,6 +1339,12 @@ static unsigned Opt_a_tosicmp (StackOpData* D)
InsertEntry (D, X, D->IP++);
} else {
if ((D->Rhs.A.Flags & LI_RELOAD_Y) == 0) {
/* ### Bug to come: This CMP uses AM65_ZP addressing mode instead
** of D->Rhs.A.LoadEntry->AM. It is subtle. Assembly formatter
** will not care, but other optimizers can bug because the stated
** mode is incorrect. Most likely, the line was copied from
** above and addressing mode never fixed.
*/
/* Cmp directly with RHS src */
X = NewCodeEntry (OP65_CMP, AM65_ZP, D->Rhs.A.LoadEntry->Arg, 0, D->OpEntry->LI);
InsertEntry (D, X, D->IP++);
@@ -1462,6 +1527,10 @@ static unsigned Opt_a_tosxor (StackOpData* D)
/* Note: A subopt MUST commit to every use case (precondition) that it
** advertises here. Unhandled advertised cases will result in stack corruption,
** because OptStackOps() is committed at the point of call and cannot back out.
*/
/* The first column of these two tables must be sorted in lexical order */
/* CAUTION: table must be sorted for bsearch */
@@ -1941,6 +2010,9 @@ 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;
@@ -1949,6 +2021,12 @@ unsigned OptStackOps (CodeSeg* S)
/* Subroutine call: Check if this is one of the functions,
** we're going to replace.
*/
/* ### Note: A-only subopts are greedy here. When an A-only
** subopt exists (by name), only its preconditions are ever
** checked. There is no fallback to the full A/X subopts.
** When the A-only preconditions fail, good A/X cases are
** left unoptimized.
*/
if (SameRegXValue (&Data)) {
Data.OptFunc = FindFunc (FuncRegATable, FUNC_COUNT (FuncRegATable), E->Arg);
IsRegAOptFunc = 1;
@@ -2071,6 +2149,9 @@ unsigned OptStackOps (CodeSeg* S)
** load tracking but at least a/x has probably lost between
** pushax and here and will be tracked again when restarting.
*/
/* ### Note: PreCondOk() and RegAPreCondOk() should be merged
** into a single precondition system.
*/
if (IsRegAOptFunc ? !RegAPreCondOk (&Data) : !PreCondOk (&Data)) {
/* Unflag entries that can't be removed */
ResetDontRemoveEntryFlags (&Data);