[NFC][TableGen] Refactor DecoderEmitter.cpp #135510
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topperc
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Apr 13, 2025
- Add helper functions to insert ULEB128 encoded value and NumToSkip.
- Use ArrayRef<> instead of const vector references as function
arguments.
- Return `OpHasCompleteDecoder` by value instead of by reference.
- Use range for loops.
- Remove {} around single line if/else bodies.
- In `emitSoftFailTableEntry`, unconditionally emit the Positive and
Negative mask values, instead of explicitly emitting a 0 byte when
the mask is not needed.
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@llvm/pr-subscribers-tablegen Author: Rahul Joshi (jurahul) Changes
Patch is 23.95 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/135510.diff 1 Files Affected:
diff --git a/llvm/utils/TableGen/DecoderEmitter.cpp b/llvm/utils/TableGen/DecoderEmitter.cpp
index ecf9c84f86a6d..14fb96bdfcfbf 100644
--- a/llvm/utils/TableGen/DecoderEmitter.cpp
+++ b/llvm/utils/TableGen/DecoderEmitter.cpp
@@ -76,8 +76,6 @@ static cl::opt<SuppressLevel> DecoderEmitterSuppressDuplicates(
"significantly reducing Table Duplications")),
cl::init(SUPPRESSION_DISABLE), cl::cat(DisassemblerEmitterCat));
-namespace {
-
STATISTIC(NumEncodings, "Number of encodings considered");
STATISTIC(NumEncodingsLackingDisasm,
"Number of encodings without disassembler info");
@@ -85,6 +83,8 @@ STATISTIC(NumInstructions, "Number of instructions considered");
STATISTIC(NumEncodingsSupported, "Number of encodings supported");
STATISTIC(NumEncodingsOmitted, "Number of encodings omitted");
+namespace {
+
struct EncodingField {
unsigned Base, Width, Offset;
EncodingField(unsigned B, unsigned W, unsigned O)
@@ -98,7 +98,7 @@ struct OperandInfo {
uint64_t InitValue;
OperandInfo(std::string D, bool HCD)
- : Decoder(std::move(D)), HasCompleteDecoder(HCD), InitValue(0) {}
+ : Decoder(D), HasCompleteDecoder(HCD), InitValue(0) {}
void addField(unsigned Base, unsigned Width, unsigned Offset) {
Fields.push_back(EncodingField(Base, Width, Offset));
@@ -112,12 +112,28 @@ struct OperandInfo {
const_iterator end() const { return Fields.end(); }
};
-typedef std::vector<uint8_t> DecoderTable;
-typedef uint32_t DecoderFixup;
-typedef std::vector<DecoderFixup> FixupList;
+typedef std::vector<uint32_t> FixupList;
typedef std::vector<FixupList> FixupScopeList;
typedef SmallSetVector<CachedHashString, 16> PredicateSet;
typedef SmallSetVector<CachedHashString, 16> DecoderSet;
+
+struct DecoderTable : public std::vector<uint8_t> {
+ // Insert a ULEB128 encoded value into the table.
+ void insertULEB128(uint64_t Value) {
+ // Encode and emit the value to filter against.
+ uint8_t Buffer[16];
+ unsigned Len = encodeULEB128(Value, Buffer);
+ insert(end(), Buffer, Buffer + Len);
+ }
+
+ // Insert space for `NumToSkip` and return the position
+ // in the table for patching.
+ size_t insertNumToSkip() {
+ size_t Size = size();
+ insert(end(), 3, 0);
+ return Size;
+ }
+};
struct DecoderTableInfo {
DecoderTable Table;
FixupScopeList FixupStack;
@@ -167,7 +183,7 @@ class DecoderEmitter {
unsigned BitWidth, StringRef Namespace,
const EncodingIDsVec &EncodingIDs) const;
void emitInstrLenTable(formatted_raw_ostream &OS,
- std::vector<unsigned> &InstrLen) const;
+ ArrayRef<unsigned> InstrLen) const;
void emitPredicateFunction(formatted_raw_ostream &OS,
PredicateSet &Predicates, indent Indent) const;
void emitDecoderFunction(formatted_raw_ostream &OS, DecoderSet &Decoders,
@@ -264,7 +280,8 @@ typedef std::vector<bit_value_t> insn_t;
namespace {
-static const uint64_t NO_FIXED_SEGMENTS_SENTINEL = -1ULL;
+static constexpr uint64_t NO_FIXED_SEGMENTS_SENTINEL =
+ std::numeric_limits<uint64_t>::max();
class FilterChooser;
@@ -343,8 +360,7 @@ class Filter {
// Return the filter chooser for the group of instructions without constant
// segment values.
const FilterChooser &getVariableFC() const {
- assert(NumFiltered == 1);
- assert(FilterChooserMap.size() == 1);
+ assert(NumFiltered == 1 && FilterChooserMap.size() == 1);
return *(FilterChooserMap.find(NO_FIXED_SEGMENTS_SENTINEL)->second);
}
@@ -365,17 +381,15 @@ class Filter {
unsigned usefulness() const;
}; // end class Filter
-} // end anonymous namespace
-
// These are states of our finite state machines used in FilterChooser's
// filterProcessor() which produces the filter candidates to use.
-typedef enum {
+enum bitAttr_t {
ATTR_NONE,
ATTR_FILTERED,
ATTR_ALL_SET,
ATTR_ALL_UNSET,
ATTR_MIXED
-} bitAttr_t;
+};
/// FilterChooser - FilterChooser chooses the best filter among a set of Filters
/// in order to perform the decoding of instructions at the current level.
@@ -392,7 +406,6 @@ typedef enum {
/// It is useful to think of a Filter as governing the switch stmts of the
/// decoding tree. And each case is delegated to an inferior FilterChooser to
/// decide what further remaining bits to look at.
-namespace {
class FilterChooser {
protected:
@@ -404,7 +417,7 @@ class FilterChooser {
// Vector of uid's for this filter chooser to work on.
// The first member of the pair is the opcode id being decoded, the second is
// the opcode id that should be emitted.
- const std::vector<EncodingIDAndOpcode> &Opcodes;
+ ArrayRef<EncodingIDAndOpcode> Opcodes;
// Lookup table for the operand decoding of instructions.
const std::map<unsigned, std::vector<OperandInfo>> &Operands;
@@ -436,7 +449,7 @@ class FilterChooser {
public:
FilterChooser(ArrayRef<EncodingAndInst> Insts,
- const std::vector<EncodingIDAndOpcode> &IDs,
+ ArrayRef<EncodingIDAndOpcode> IDs,
const std::map<unsigned, std::vector<OperandInfo>> &Ops,
unsigned BW, const DecoderEmitter *E)
: AllInstructions(Insts), Opcodes(IDs), Operands(Ops),
@@ -446,7 +459,7 @@ class FilterChooser {
}
FilterChooser(ArrayRef<EncodingAndInst> Insts,
- const std::vector<EncodingIDAndOpcode> &IDs,
+ ArrayRef<EncodingIDAndOpcode> IDs,
const std::map<unsigned, std::vector<OperandInfo>> &Ops,
const std::vector<bit_value_t> &ParentFilterBitValues,
const FilterChooser &parent)
@@ -502,8 +515,7 @@ class FilterChooser {
/// dumpFilterArray - dumpFilterArray prints out debugging info for the given
/// filter array as a series of chars.
- void dumpFilterArray(raw_ostream &OS,
- const std::vector<bit_value_t> &filter) const;
+ void dumpFilterArray(raw_ostream &OS, ArrayRef<bit_value_t> Filter) const;
/// dumpStack - dumpStack traverses the filter chooser chain and calls
/// dumpFilterArray on each filter chooser up to the top level one.
@@ -544,14 +556,12 @@ class FilterChooser {
void emitSingletonTableEntry(DecoderTableInfo &TableInfo,
const Filter &Best) const;
- void emitBinaryParser(raw_ostream &OS, indent Indent,
- const OperandInfo &OpInfo,
- bool &OpHasCompleteDecoder) const;
+ bool emitBinaryParser(raw_ostream &OS, indent Indent,
+ const OperandInfo &OpInfo) const;
- void emitDecoder(raw_ostream &OS, indent Indent, unsigned Opc,
- bool &HasCompleteDecoder) const;
- unsigned getDecoderIndex(DecoderSet &Decoders, unsigned Opc,
- bool &HasCompleteDecoder) const;
+ bool emitDecoder(raw_ostream &OS, indent Indent, unsigned Opc) const;
+ std::pair<unsigned, bool> getDecoderIndex(DecoderSet &Decoders,
+ unsigned Opc) const;
// Assign a single filter and run with it.
void runSingleFilter(unsigned startBit, unsigned numBit, bool mixed);
@@ -659,7 +669,6 @@ void Filter::recurse() {
// Otherwise, create sub choosers.
for (const auto &Inst : FilteredInstructions) {
-
// Marks all the segment positions with either BIT_TRUE or BIT_FALSE.
for (unsigned bitIndex = 0; bitIndex < NumBits; ++bitIndex) {
if (Inst.first & (1ULL << bitIndex))
@@ -681,13 +690,11 @@ static void resolveTableFixups(DecoderTable &Table, const FixupList &Fixups,
uint32_t DestIdx) {
// Any NumToSkip fixups in the current scope can resolve to the
// current location.
- for (FixupList::const_reverse_iterator I = Fixups.rbegin(), E = Fixups.rend();
- I != E; ++I) {
+ for (uint32_t FixupIdx : reverse(Fixups)) {
// Calculate the distance from the byte following the fixup entry byte
// to the destination. The Target is calculated from after the 24-bit
// NumToSkip entry itself, so subtract three from the displacement here
// to account for that.
- uint32_t FixupIdx = *I;
uint32_t Delta = DestIdx - FixupIdx - 3;
// Our NumToSkip entries are 24-bits. Make sure our table isn't too
// big.
@@ -704,10 +711,7 @@ void Filter::emitTableEntry(DecoderTableInfo &TableInfo) const {
assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
TableInfo.Table.push_back(MCD::OPC_ExtractField);
- SmallString<16> SBytes;
- raw_svector_ostream S(SBytes);
- encodeULEB128(StartBit, S);
- TableInfo.Table.insert(TableInfo.Table.end(), SBytes.begin(), SBytes.end());
+ TableInfo.Table.insertULEB128(StartBit);
TableInfo.Table.push_back(NumBits);
// A new filter entry begins a new scope for fixup resolution.
@@ -733,16 +737,10 @@ void Filter::emitTableEntry(DecoderTableInfo &TableInfo) const {
PrevFilter = 0; // Don't re-process the filter's fallthrough.
} else {
Table.push_back(MCD::OPC_FilterValue);
- // Encode and emit the value to filter against.
- uint8_t Buffer[16];
- unsigned Len = encodeULEB128(Filter.first, Buffer);
- Table.insert(Table.end(), Buffer, Buffer + Len);
+ Table.insertULEB128(Filter.first);
// Reserve space for the NumToSkip entry. We'll backpatch the value
// later.
- PrevFilter = Table.size();
- Table.push_back(0);
- Table.push_back(0);
- Table.push_back(0);
+ PrevFilter = Table.insertNumToSkip();
}
// We arrive at a category of instructions with the same segment value.
@@ -779,10 +777,7 @@ void Filter::emitTableEntry(DecoderTableInfo &TableInfo) const {
// Returns the number of fanout produced by the filter. More fanout implies
// the filter distinguishes more categories of instructions.
unsigned Filter::usefulness() const {
- if (!VariableInstructions.empty())
- return FilteredInstructions.size();
- else
- return FilteredInstructions.size() + 1;
+ return FilteredInstructions.size() + VariableInstructions.empty();
}
//////////////////////////////////
@@ -982,11 +977,10 @@ void DecoderEmitter::emitTable(formatted_raw_ostream &OS, DecoderTable &Table,
}
void DecoderEmitter::emitInstrLenTable(formatted_raw_ostream &OS,
- std::vector<unsigned> &InstrLen) const {
+ ArrayRef<unsigned> InstrLen) const {
OS << "static const uint8_t InstrLenTable[] = {\n";
- for (unsigned &Len : InstrLen) {
+ for (unsigned Len : InstrLen)
OS << Len << ",\n";
- }
OS << "};\n\n";
}
@@ -1037,9 +1031,8 @@ void DecoderEmitter::emitDecoderFunction(formatted_raw_ostream &OS,
OS << Indent << "TmpType tmp;\n";
OS << Indent << "switch (Idx) {\n";
OS << Indent << "default: llvm_unreachable(\"Invalid index!\");\n";
- unsigned Index = 0;
- for (const auto &Decoder : Decoders) {
- OS << Indent << "case " << Index++ << ":\n";
+ for (const auto &[Index, Decoder] : enumerate(Decoders)) {
+ OS << Indent << "case " << Index << ":\n";
OS << Decoder;
OS << Indent + 2 << "return S;\n";
}
@@ -1072,10 +1065,10 @@ std::pair<bool, uint64_t> FilterChooser::fieldFromInsn(const insn_t &Insn,
/// dumpFilterArray - dumpFilterArray prints out debugging info for the given
/// filter array as a series of chars.
-void FilterChooser::dumpFilterArray(
- raw_ostream &OS, const std::vector<bit_value_t> &filter) const {
+void FilterChooser::dumpFilterArray(raw_ostream &OS,
+ ArrayRef<bit_value_t> Filter) const {
for (unsigned bitIndex = BitWidth; bitIndex > 0; bitIndex--) {
- switch (filter[bitIndex - 1]) {
+ switch (Filter[bitIndex - 1]) {
case BIT_UNFILTERED:
OS << ".";
break;
@@ -1127,9 +1120,9 @@ unsigned FilterChooser::getIslands(std::vector<Island> &Islands,
llvm_unreachable("Unreachable code!");
case 0:
case 1:
- if (Filtered || Val == -1)
+ if (Filtered || Val == -1) {
State = 1; // Still in Water
- else {
+ } else {
State = 2; // Into the Island
StartBit = i;
FieldVal = Val;
@@ -1153,9 +1146,8 @@ unsigned FilterChooser::getIslands(std::vector<Island> &Islands,
return Islands.size();
}
-void FilterChooser::emitBinaryParser(raw_ostream &OS, indent Indent,
- const OperandInfo &OpInfo,
- bool &OpHasCompleteDecoder) const {
+bool FilterChooser::emitBinaryParser(raw_ostream &OS, indent Indent,
+ const OperandInfo &OpInfo) const {
const std::string &Decoder = OpInfo.Decoder;
bool UseInsertBits = OpInfo.numFields() != 1 || OpInfo.InitValue != 0;
@@ -1180,6 +1172,7 @@ void FilterChooser::emitBinaryParser(raw_ostream &OS, indent Indent,
OS << ";\n";
}
+ bool OpHasCompleteDecoder;
if (Decoder != "") {
OpHasCompleteDecoder = OpInfo.HasCompleteDecoder;
OS << Indent << "if (!Check(S, " << Decoder
@@ -1190,11 +1183,12 @@ void FilterChooser::emitBinaryParser(raw_ostream &OS, indent Indent,
OpHasCompleteDecoder = true;
OS << Indent << "MI.addOperand(MCOperand::createImm(tmp));\n";
}
+ return OpHasCompleteDecoder;
}
-void FilterChooser::emitDecoder(raw_ostream &OS, indent Indent, unsigned Opc,
- bool &HasCompleteDecoder) const {
- HasCompleteDecoder = true;
+bool FilterChooser::emitDecoder(raw_ostream &OS, indent Indent,
+ unsigned Opc) const {
+ bool HasCompleteDecoder = true;
for (const auto &Op : Operands.find(Opc)->second) {
// If a custom instruction decoder was specified, use that.
@@ -1207,21 +1201,19 @@ void FilterChooser::emitDecoder(raw_ostream &OS, indent Indent, unsigned Opc,
break;
}
- bool OpHasCompleteDecoder;
- emitBinaryParser(OS, Indent, Op, OpHasCompleteDecoder);
- if (!OpHasCompleteDecoder)
- HasCompleteDecoder = false;
+ HasCompleteDecoder &= emitBinaryParser(OS, Indent, Op);
}
+ return HasCompleteDecoder;
}
-unsigned FilterChooser::getDecoderIndex(DecoderSet &Decoders, unsigned Opc,
- bool &HasCompleteDecoder) const {
+std::pair<unsigned, bool> FilterChooser::getDecoderIndex(DecoderSet &Decoders,
+ unsigned Opc) const {
// Build up the predicate string.
SmallString<256> Decoder;
// FIXME: emitDecoder() function can take a buffer directly rather than
// a stream.
raw_svector_ostream S(Decoder);
- emitDecoder(S, indent(4), Opc, HasCompleteDecoder);
+ bool HasCompleteDecoder = emitDecoder(S, indent(4), Opc);
// Using the full decoder string as the key value here is a bit
// heavyweight, but is effective. If the string comparisons become a
@@ -1233,7 +1225,7 @@ unsigned FilterChooser::getDecoderIndex(DecoderSet &Decoders, unsigned Opc,
Decoders.insert(CachedHashString(Decoder));
// Now figure out the index for when we write out the table.
DecoderSet::const_iterator P = find(Decoders, Decoder.str());
- return (unsigned)(P - Decoders.begin());
+ return {(unsigned)(P - Decoders.begin()), HasCompleteDecoder};
}
// If ParenIfBinOp is true, print a surrounding () if Val uses && or ||.
@@ -1336,18 +1328,12 @@ void FilterChooser::emitPredicateTableEntry(DecoderTableInfo &TableInfo,
// Figure out the index into the predicate table for the predicate just
// computed.
unsigned PIdx = getPredicateIndex(TableInfo, PS.str());
- SmallString<16> PBytes;
- raw_svector_ostream S(PBytes);
- encodeULEB128(PIdx, S);
TableInfo.Table.push_back(MCD::OPC_CheckPredicate);
- // Predicate index.
- llvm::append_range(TableInfo.Table, PBytes);
+ TableInfo.Table.insertULEB128(PIdx);
+
// Push location for NumToSkip backpatching.
- TableInfo.FixupStack.back().push_back(TableInfo.Table.size());
- TableInfo.Table.push_back(0);
- TableInfo.Table.push_back(0);
- TableInfo.Table.push_back(0);
+ TableInfo.FixupStack.back().push_back(TableInfo.Table.insertNumToSkip());
}
void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
@@ -1396,20 +1382,8 @@ void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
return;
TableInfo.Table.push_back(MCD::OPC_SoftFail);
-
- SmallString<16> MaskBytes;
- raw_svector_ostream S(MaskBytes);
- if (NeedPositiveMask) {
- encodeULEB128(PositiveMask.getZExtValue(), S);
- llvm::append_range(TableInfo.Table, MaskBytes);
- } else
- TableInfo.Table.push_back(0);
- if (NeedNegativeMask) {
- MaskBytes.clear();
- encodeULEB128(NegativeMask.getZExtValue(), S);
- llvm::append_range(TableInfo.Table, MaskBytes);
- } else
- TableInfo.Table.push_back(0);
+ TableInfo.Table.insertULEB128(PositiveMask.getZExtValue());
+ TableInfo.Table.insertULEB128(NegativeMask.getZExtValue());
}
// Emits table entries to decode the singleton.
@@ -1420,38 +1394,34 @@ void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
insnWithID(Insn, Opc.EncodingID);
// Look for islands of undecoded bits of the singleton.
- unsigned Size = getIslands(Islands, Insn);
+ getIslands(Islands, Insn);
// Emit the predicate table entry if one is needed.
emitPredicateTableEntry(TableInfo, Opc.EncodingID);
// Check any additional encoding fields needed.
- for (unsigned I = Size; I != 0; --I) {
- unsigned NumBits = Islands[I - 1].NumBits;
+ for (const Island &Ilnd : reverse(Islands)) {
+ unsigned NumBits = Ilnd.NumBits;
assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
TableInfo.Table.push_back(MCD::OPC_CheckField);
- uint8_t Buffer[16];
- unsigned Len = encodeULEB128(Islands[I - 1].StartBit, Buffer);
- TableInfo.Table.insert(TableInfo.Table.end(), Buffer, Buffer + Len);
+
+ TableInfo.Table.insertULEB128(Ilnd.StartBit);
TableInfo.Table.push_back(NumBits);
- Len = encodeULEB128(Islands[I - 1].FieldVal, Buffer);
- TableInfo.Table.insert(TableInfo.Table.end(), Buffer, Buffer + Len);
- // Push location for NumToSkip backpatching.
- TableInfo.FixupStack.back().push_back(TableInfo.Table.size());
+ TableInfo.Table.insertULEB128(Ilnd.FieldVal);
+
// The fixup is always 24-bits, so go ahead and allocate the space
// in the table so all our relative position calculations work OK even
// before we fully resolve the real value here.
- TableInfo.Table.push_back(0);
- TableInfo.Table.push_back(0);
- TableInfo.Table.push_back(0);
+
+ // Push location for NumToSkip backpatching.
+ TableInfo.FixupStack.back().push_back(TableInfo.Table.insertNumToSkip());
}
// Check for soft failure of the match.
emitSoftFailTableEntry(TableInfo, Opc.EncodingID);
- bool HasCompleteDecoder;
- unsigned DIdx =
- getDecoderIndex(TableInfo.Decoders, Opc.EncodingID, HasCompleteDecoder);
+ auto [DIdx, HasCompleteDecoder] =
+ getDecoderIndex(TableInfo.Decoders, Opc.EncodingID);
// Produce OPC_Decode or OPC_TryDecode opcode based on the information
// whether the instruction decoder is complete or not. If it is complete
@@ -1465,24 +1435,12 @@ void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
TableInfo.Table.push_back(HasCompleteDecoder ? MCD::OPC_Decode
: MCD::OPC_TryDecode);
NumEncodingsSupported++;
- uint8_t Buffer[16];
- unsigned Len = encodeULEB128(Opc.Opcode, Buffer);
- TableInfo.Table.insert(TableInfo.Table.end(), Buffer, Buffer + Len);
-
- SmallString<16> Bytes;
- raw_svector_ostream S(Bytes);
- encodeULEB128(DIdx, S);
-
- // Decoder index.
- llvm::append_range(TableInfo.Table, Bytes);
+ TableInfo.Table.insertULEB128(Opc.Opcode);
+ TableInfo.Table.insertULEB128(DIdx);
if (!HasCompleteDecoder) {
// Push location for NumToSkip backpatching.
- TableInfo.FixupStack.back().push_back(TableInfo.Table.size());
- // Allocate the space for the fixup.
- TableInfo.Table.push_back(0);
- TableInfo.Table.push_back(0);
- TableInfo.Table.push_back(0);
+ TableInfo.FixupStack.back().push_back(TableInfo.Table.insertNumToSkip());
}
}
@@ -1845,8 +1803,6 @@ static std::string findOperandDecoderMethod(const Record *Record) {
}
OperandInfo getOp...
[truncated]
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arguments.
OpHasCompleteDecoderby value instead of by reference.emitSoftFailTableEntry, unconditionally emit the Positive andNegative mask values, instead of explicitly emitting a 0 byte when
the mask is not needed.