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[TableGen][DecoderEmitter] Add a couple of helper methods (NFC) #155163

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Aug 24, 2025
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[TableGen][DecoderEmitter] Add a couple of helper methods (NFC) #155163

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59 changes: 32 additions & 27 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -252,15 +252,23 @@ class DecoderTable {
DecoderTable() { Data.reserve(16384); }

void clear() { Data.clear(); }
void push_back(uint8_t Item) { Data.push_back(Item); }
size_t size() const { return Data.size(); }
const uint8_t *data() const { return Data.data(); }

using const_iterator = std::vector<uint8_t>::const_iterator;
const_iterator begin() const { return Data.begin(); }
const_iterator end() const { return Data.end(); }

// Insert a ULEB128 encoded value into the table.
/// Inserts a state machine opcode into the table.
void insertOpcode(MCD::DecoderOps Opcode) { Data.push_back(Opcode); }

/// Inserts a uint8 encoded value into the table.
void insertUInt8(unsigned Value) {
assert(isUInt<8>(Value));
Data.push_back(Value);
}

/// Inserts a ULEB128 encoded value into the table.
void insertULEB128(uint64_t Value) {
// Encode and emit the value to filter against.
uint8_t Buffer[16];
Expand Down Expand Up @@ -1243,10 +1251,10 @@ void FilterChooser::emitPredicateTableEntry(DecoderTableInfo &TableInfo,
// computed.
unsigned PIdx = getPredicateIndex(TableInfo, PS.str());

const uint8_t DecoderOp = TableInfo.isOutermostScope()
? MCD::OPC_CheckPredicateOrFail
: MCD::OPC_CheckPredicate;
TableInfo.Table.push_back(DecoderOp);
const MCD::DecoderOps DecoderOp = TableInfo.isOutermostScope()
? MCD::OPC_CheckPredicateOrFail
: MCD::OPC_CheckPredicate;
TableInfo.Table.insertOpcode(DecoderOp);
TableInfo.Table.insertULEB128(PIdx);

if (DecoderOp == MCD::OPC_CheckPredicate) {
Expand Down Expand Up @@ -1286,7 +1294,7 @@ void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
if (!NeedPositiveMask && !NeedNegativeMask)
return;

TableInfo.Table.push_back(MCD::OPC_SoftFail);
TableInfo.Table.insertOpcode(MCD::OPC_SoftFail);
TableInfo.Table.insertULEB128(PositiveMask.getZExtValue());
TableInfo.Table.insertULEB128(NegativeMask.getZExtValue());
}
Expand All @@ -1305,14 +1313,12 @@ void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,

// Check any additional encoding fields needed.
for (const Island &Ilnd : reverse(Islands)) {
assert(isUInt<8>(Ilnd.NumBits) && "NumBits overflowed uint8 table entry!");
const uint8_t DecoderOp = TableInfo.isOutermostScope()
? MCD::OPC_CheckFieldOrFail
: MCD::OPC_CheckField;
TableInfo.Table.push_back(DecoderOp);

const MCD::DecoderOps DecoderOp = TableInfo.isOutermostScope()
? MCD::OPC_CheckFieldOrFail
: MCD::OPC_CheckField;
TableInfo.Table.insertOpcode(DecoderOp);
TableInfo.Table.insertULEB128(Ilnd.StartBit);
TableInfo.Table.push_back(Ilnd.NumBits);
TableInfo.Table.insertUInt8(Ilnd.NumBits);
TableInfo.Table.insertULEB128(Ilnd.FieldVal);

if (DecoderOp == MCD::OPC_CheckField) {
Expand All @@ -1338,12 +1344,11 @@ void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
// decoder method indicates that additional processing should be done to see
// if there is any other instruction that also matches the bitpattern and
// can decode it.
const uint8_t DecoderOp =
Encoding.hasCompleteDecoder()
? MCD::OPC_Decode
: (TableInfo.isOutermostScope() ? MCD::OPC_TryDecodeOrFail
: MCD::OPC_TryDecode);
TableInfo.Table.push_back(DecoderOp);
const MCD::DecoderOps DecoderOp =
Encoding.hasCompleteDecoder() ? MCD::OPC_Decode
: TableInfo.isOutermostScope() ? MCD::OPC_TryDecodeOrFail
: MCD::OPC_TryDecode;
TableInfo.Table.insertOpcode(DecoderOp);
const Record *InstDef = Encodings[EncodingID].getInstruction()->TheDef;
TableInfo.Table.insertULEB128(Emitter->getTarget().getInstrIntValue(InstDef));
TableInfo.Table.insertULEB128(DIdx);
Expand Down Expand Up @@ -1661,14 +1666,13 @@ void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
} else {
// The general case: emit a switch over the field value.
DecoderTable &Table = TableInfo.Table;
Table.push_back(MCD::OPC_ExtractField);
Table.insertOpcode(MCD::OPC_ExtractField);
Table.insertULEB128(StartBit);
assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
Table.push_back(NumBits);
Table.insertUInt8(NumBits);

// Emit switch cases for all but the last element.
for (const auto &[FilterVal, Delegate] : drop_end(FilterChooserMap)) {
Table.push_back(MCD::OPC_FilterValue);
Table.insertOpcode(MCD::OPC_FilterValue);
Table.insertULEB128(FilterVal);
size_t FixupPos = Table.insertNumToSkip();

Expand All @@ -1682,8 +1686,9 @@ void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
// Emit a switch case for the last element. It never falls through;
// if it doesn't match, we leave the current scope.
const auto &[FilterVal, Delegate] = *FilterChooserMap.rbegin();
Table.push_back(!TableInfo.isOutermostScope() ? MCD::OPC_FilterValue
: MCD::OPC_FilterValueOrFail);
Table.insertOpcode(!TableInfo.isOutermostScope()
? MCD::OPC_FilterValue
: MCD::OPC_FilterValueOrFail);
Table.insertULEB128(FilterVal);
if (!TableInfo.isOutermostScope())
TableInfo.FixupStack.back().push_back(Table.insertNumToSkip());
Expand Down Expand Up @@ -2519,7 +2524,7 @@ namespace {
assert(TableInfo.isOutermostScope() && "fixup stack phasing error!");
TableInfo.popScope();

TableInfo.Table.push_back(MCD::OPC_Fail);
TableInfo.Table.insertOpcode(MCD::OPC_Fail);

// Print the table to the output stream.
OpcodeMask |= emitTable(OS, TableInfo.Table, DecoderNamespace, HwModeID,
Expand Down
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