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[TableGen][DecoderEmitter] Move a function to InstructionEncoding (NFC) #155038

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Merged
merged 1 commit into from
Aug 22, 2025
+23 −19
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[TableGen][DecoderEmitter] Move a function to InstructionEncoding (NFC) #155038

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42 changes: 23 additions & 19 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -199,6 +199,17 @@ class InstructionEncoding {
/// Returns a mask of bits that should be considered unknown during decoding.
const APInt &getSoftFailBits() const { return SoftFailBits; }

/// Returns the known bits of this encoding that must match for
/// successful decoding.
KnownBits getMandatoryBits() const {
KnownBits EncodingBits = InstBits;
// Mark all bits that are allowed to change according to SoftFail mask
// as unknown.
EncodingBits.Zero &= ~SoftFailBits;
EncodingBits.One &= ~SoftFailBits;
return EncodingBits;
}

/// Returns the name of the function to use for decoding, or an empty string
/// if the decoder is generated.
StringRef getDecoderMethod() const { return DecoderMethod; }
Expand Down Expand Up @@ -559,15 +570,6 @@ class FilterChooser {
}

protected:
KnownBits getMandatoryEncodingBits(unsigned EncodingID) const {
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getInstBits();
// Clear all bits that are allowed to change according to SoftFail mask.
EncodingBits.Zero &= ~Encoding.getSoftFailBits();
EncodingBits.One &= ~Encoding.getSoftFailBits();
return EncodingBits;
}

/// dumpStack - dumpStack traverses the filter chooser chain and calls
/// dumpFilterArray on each filter chooser up to the top level one.
void dumpStack(raw_ostream &OS, indent Indent, unsigned PadToWidth) const;
Expand Down Expand Up @@ -655,8 +657,8 @@ Filter::Filter(const FilterChooser &owner, unsigned startBit, unsigned numBits)
assert(StartBit + NumBits - 1 < Owner.FilterBits.getBitWidth());

for (unsigned EncodingID : Owner.EncodingIDs) {
// Populates the insn given the uid.
KnownBits EncodingBits = Owner.getMandatoryEncodingBits(EncodingID);
const InstructionEncoding &Encoding = Owner.Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();

// Scans the segment for possibly well-specified encoding bits.
KnownBits FieldBits = EncodingBits.extractBits(NumBits, StartBit);
Expand Down Expand Up @@ -1381,7 +1383,8 @@ void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
// Emits table entries to decode the singleton.
void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const {
KnownBits EncodingBits = getMandatoryEncodingBits(EncodingID);
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();

// Look for islands of undecoded bits of the singleton.
std::vector<Island> Islands = getIslands(EncodingBits);
Expand Down Expand Up @@ -1425,7 +1428,6 @@ 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 InstructionEncoding &Encoding = Encodings[EncodingID];
const uint8_t DecoderOp =
Encoding.hasCompleteDecoder()
? MCD::OPC_Decode
Expand Down Expand Up @@ -1484,7 +1486,8 @@ bool FilterChooser::filterProcessor(ArrayRef<bitAttr_t> BitAttrs,
assert(EncodingIDs.size() == 3);

for (unsigned EncodingID : EncodingIDs) {
KnownBits EncodingBits = getMandatoryEncodingBits(EncodingID);
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();

// Look for islands of undecoded bits of any instruction.
std::vector<Island> Islands = getIslands(EncodingBits);
Expand Down Expand Up @@ -1675,7 +1678,8 @@ void FilterChooser::doFilter() {
BitAttrs[BitIndex] = ATTR_FILTERED;

for (unsigned EncodingID : EncodingIDs) {
KnownBits EncodingBits = getMandatoryEncodingBits(EncodingID);
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();

for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++BitIndex) {
bool IsKnown = EncodingBits.Zero[BitIndex] || EncodingBits.One[BitIndex];
Expand Down Expand Up @@ -1732,10 +1736,10 @@ void FilterChooser::doFilter() {

// Dump encodings.
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Enc = Encodings[EncodingID];
errs() << Indent << indent(PadToWidth - Enc.getBitWidth());
printKnownBits(errs(), getMandatoryEncodingBits(EncodingID), '_');
errs() << " " << Enc.getName() << '\n';
const InstructionEncoding &Encoding = Encodings[EncodingID];
errs() << Indent << indent(PadToWidth - Encoding.getBitWidth());
printKnownBits(errs(), Encoding.getMandatoryBits(), '_');
errs() << " " << Encoding.getName() << '\n';
}
PrintFatalError("Decoding conflict encountered");
}
Expand Down