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[TableGen][DecoderEmitter] Replace opcode mask with booleans (NFC) #159113

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Merged
merged 3 commits into from
Sep 16, 2025
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[TableGen][DecoderEmitter] Replace opcode mask with booleans (NFC) #159113

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[TableGen][DecoderEmitter] Replace opcode mask with booleans (NFC)
s-barannikov Sep 16, 2025
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s-barannikov Sep 16, 2025
59ab098
Remove unused variable
s-barannikov Sep 16, 2025
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61 changes: 27 additions & 34 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -226,6 +226,9 @@ struct DecoderTableInfo {
DecoderTable Table;
PredicateSet Predicates;
DecoderSet Decoders;
bool HasCheckPredicate;
bool HasSoftFail;
bool HasTryDecode;

void insertPredicate(StringRef Predicate) {
Predicates.insert(CachedHashString(Predicate));
Expand Down Expand Up @@ -266,11 +269,10 @@ class DecoderEmitter {

const CodeGenTarget &getTarget() const { return Target; }

// Emit the decoder state machine table. Returns a mask of MCD decoder ops
// that were emitted.
unsigned emitTable(formatted_raw_ostream &OS, DecoderTable &Table,
StringRef Namespace, unsigned HwModeID, unsigned BitWidth,
ArrayRef<unsigned> EncodingIDs) const;
// Emit the decoder state machine table.
void emitTable(formatted_raw_ostream &OS, DecoderTableInfo &TableInfo,
StringRef Namespace, unsigned HwModeID, unsigned BitWidth,
ArrayRef<unsigned> EncodingIDs) const;
void emitInstrLenTable(formatted_raw_ostream &OS,
ArrayRef<unsigned> InstrLen) const;
void emitPredicateFunction(formatted_raw_ostream &OS,
Expand Down Expand Up @@ -629,12 +631,11 @@ static StringRef getDecoderOpName(DecoderOps Op) {
llvm_unreachable("Unknown decoder op");
}

// Emit the decoder state machine table. Returns a mask of MCD decoder ops
// that were emitted.
unsigned DecoderEmitter::emitTable(formatted_raw_ostream &OS,
DecoderTable &Table, StringRef Namespace,
unsigned HwModeID, unsigned BitWidth,
ArrayRef<unsigned> EncodingIDs) const {
// Emit the decoder state machine table.
void DecoderEmitter::emitTable(formatted_raw_ostream &OS,
DecoderTableInfo &TableInfo, StringRef Namespace,
unsigned HwModeID, unsigned BitWidth,
ArrayRef<unsigned> EncodingIDs) const {
// We'll need to be able to map from a decoded opcode into the corresponding
// EncodingID for this specific combination of BitWidth and Namespace. This
// is used below to index into Encodings.
Expand All @@ -648,7 +649,7 @@ unsigned DecoderEmitter::emitTable(formatted_raw_ostream &OS,
OS << "static const uint8_t DecoderTable" << Namespace;
if (HwModeID != DefaultMode)
OS << '_' << Target.getHwModes().getModeName(HwModeID);
OS << BitWidth << "[" << Table.size() << "] = {\n";
OS << BitWidth << "[" << TableInfo.Table.size() << "] = {\n";

// Emit ULEB128 encoded value to OS, returning the number of bytes emitted.
auto EmitULEB128 = [](DecoderTable::const_iterator &I,
Expand Down Expand Up @@ -678,6 +679,7 @@ unsigned DecoderEmitter::emitTable(formatted_raw_ostream &OS,

// FIXME: We may be able to use the NumToSkip values to recover
// appropriate indentation levels.
DecoderTable &Table = TableInfo.Table;
DecoderTable::const_iterator I = Table.begin();
DecoderTable::const_iterator E = Table.end();
const uint8_t *const EndPtr = Table.data() + Table.size();
Expand Down Expand Up @@ -719,15 +721,12 @@ unsigned DecoderEmitter::emitTable(formatted_raw_ostream &OS,
return Value;
};

unsigned OpcodeMask = 0;

while (I != E) {
assert(I < E && "incomplete decode table entry!");

uint32_t Pos = I - Table.begin();
EmitPos(Pos);
const uint8_t DecoderOp = *I++;
OpcodeMask |= (1 << DecoderOp);
OS << getDecoderOpName(static_cast<DecoderOps>(DecoderOp)) << ", ";
switch (DecoderOp) {
default:
Expand Down Expand Up @@ -826,8 +825,6 @@ unsigned DecoderEmitter::emitTable(formatted_raw_ostream &OS,
OS << '\n';
}
OS << "};\n\n";

return OpcodeMask;
}

void DecoderEmitter::emitInstrLenTable(formatted_raw_ostream &OS,
Expand Down Expand Up @@ -1114,6 +1111,7 @@ void DecoderTableBuilder::emitPredicateTableEntry(unsigned EncodingID) const {

TableInfo.Table.insertOpcode(OPC_CheckPredicate);
TableInfo.Table.insertULEB128(PredicateIndex);
TableInfo.HasCheckPredicate = true;
}

void DecoderTableBuilder::emitSoftFailTableEntry(unsigned EncodingID) const {
Expand All @@ -1130,6 +1128,7 @@ void DecoderTableBuilder::emitSoftFailTableEntry(unsigned EncodingID) const {
TableInfo.Table.insertOpcode(OPC_SoftFail);
TableInfo.Table.insertULEB128(PositiveMask.getZExtValue());
TableInfo.Table.insertULEB128(NegativeMask.getZExtValue());
TableInfo.HasSoftFail = true;
}

// Emits table entries to decode the singleton.
Expand Down Expand Up @@ -1180,6 +1179,7 @@ void DecoderTableBuilder::emitSingletonTableEntry(
const Record *InstDef = Encodings[EncodingID].getInstruction()->TheDef;
TableInfo.Table.insertULEB128(Target.getInstrIntValue(InstDef));
TableInfo.Table.insertULEB128(DecoderIndex);
TableInfo.HasTryDecode |= DecoderOp == OPC_TryDecode;
}

std::unique_ptr<Filter>
Expand Down Expand Up @@ -1523,11 +1523,7 @@ void DecoderTableBuilder::emitTableEntries(const FilterChooser &FC) const {
// emitDecodeInstruction - Emit the templated helper function
// decodeInstruction().
static void emitDecodeInstruction(formatted_raw_ostream &OS, bool IsVarLenInst,
unsigned OpcodeMask) {
const bool HasTryDecode = OpcodeMask & (1 << OPC_TryDecode);
const bool HasCheckPredicate = OpcodeMask & (1 << OPC_CheckPredicate);
const bool HasSoftFail = OpcodeMask & (1 << OPC_SoftFail);

const DecoderTableInfo &TableInfo) {
OS << R"(
static unsigned decodeNumToSkip(const uint8_t *&Ptr) {
unsigned NumToSkip = *Ptr++;
Expand All @@ -1548,7 +1544,7 @@ static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,
"llvm::function_ref<void(APInt &, uint64_t)> makeUp";
}
OS << ") {\n";
if (HasCheckPredicate)
if (TableInfo.HasCheckPredicate)
OS << " const FeatureBitset &Bits = STI.getFeatureBits();\n";
OS << " const uint8_t *Ptr = DecodeTable;\n";

Expand Down Expand Up @@ -1657,7 +1653,7 @@ static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,
}
break;
})";
if (HasCheckPredicate) {
if (TableInfo.HasCheckPredicate) {
OS << R"(
case OPC_CheckPredicate: {
// Decode the Predicate Index value.
Expand Down Expand Up @@ -1701,7 +1697,7 @@ static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,
<< (S != MCDisassembler::Fail ? "PASS\n" : "FAIL\n"));
return S;
})";
if (HasTryDecode) {
if (TableInfo.HasTryDecode) {
OS << R"(
case OPC_TryDecode: {
// Decode the Opcode value.
Expand Down Expand Up @@ -1735,7 +1731,7 @@ static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,
break;
})";
}
if (HasSoftFail) {
if (TableInfo.HasSoftFail) {
OS << R"(
case OPC_SoftFail: {
// Decode the mask values.
Expand Down Expand Up @@ -1994,9 +1990,8 @@ template <typename T> constexpr uint32_t InsnBitWidth = 0;

// Entries in `EncMap` are already sorted by bitwidth. So bucketing per
// bitwidth can be done on-the-fly as we iterate over the map.
DecoderTableInfo TableInfo;
DecoderTableInfo TableInfo{};
DecoderTableBuilder TableBuilder(Target, Encodings, TableInfo);
unsigned OpcodeMask = 0;

bool HasConflict = false;
for (const auto &[BitWidth, BWMap] : EncMap) {
Expand All @@ -2021,8 +2016,8 @@ template <typename T> constexpr uint32_t InsnBitWidth = 0;
TableBuilder.buildTable(FC, BitWidth);

// Print the table to the output stream.
OpcodeMask |= emitTable(OS, TableInfo.Table, DecoderNamespace, HwModeID,
BitWidth, EncodingIDs);
emitTable(OS, TableInfo, DecoderNamespace, HwModeID, BitWidth,
EncodingIDs);
}

// Each BitWidth get's its own decoders and decoder function if
Expand All @@ -2041,14 +2036,12 @@ template <typename T> constexpr uint32_t InsnBitWidth = 0;
if (!SpecializeDecodersPerBitwidth)
emitDecoderFunction(OS, TableInfo.Decoders, 0);

const bool HasCheckPredicate = OpcodeMask & (1 << OPC_CheckPredicate);

// Emit the predicate function.
if (HasCheckPredicate)
if (TableInfo.HasCheckPredicate)
emitPredicateFunction(OS, TableInfo.Predicates);

// Emit the main entry point for the decoder, decodeInstruction().
emitDecodeInstruction(OS, IsVarLenInst, OpcodeMask);
emitDecodeInstruction(OS, IsVarLenInst, TableInfo);

OS << "\n} // namespace\n";
}
Expand Down