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[TableGen][DecoderEmitter] Improve conflicts dump #154001

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merged 2 commits into from
Aug 17, 2025
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[TableGen][DecoderEmitter] Improve conflicts dump #154001

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8f636db
[TableGen][DecoderEmitter] Improve conflicts dump
s-barannikov Aug 17, 2025
e562d23
Update the failing test
s-barannikov Aug 17, 2025
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8 changes: 4 additions & 4 deletions llvm/test/TableGen/FixedLenDecoderEmitter/conflict.td
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@ def B : I<(outs GPR32:$dst), (ins GPR32:$src1), []> {
}

// CHECK: Decoding Conflict:
// CHECK: 00000000000000000000000000000000
// CHECK: ................................
// CHECK: A 00000000000000000000000000000000
// CHECK: B 00000000000000000000000000000000
// CHECK: ................................
// CHECK: 00000000000000000000000000000000
// CHECK: 00000000000000000000000000000000 A
// CHECK: 00000000000000000000000000000000 B
57 changes: 28 additions & 29 deletions llvm/utils/TableGen/DecoderEmitter.cpp
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Expand Up @@ -319,8 +319,8 @@ static raw_ostream &operator<<(raw_ostream &OS, const EncodingAndInst &Value) {
}

// Prints the bit value for each position.
static void dumpBits(raw_ostream &OS, const BitsInit &Bits) {
for (const Init *Bit : reverse(Bits.getBits()))
static void dumpBits(raw_ostream &OS, const BitsInit &Bits, unsigned BitWidth) {
for (const Init *Bit : reverse(Bits.getBits().take_front(BitWidth)))
OS << BitValue(Bit);
}

Expand Down Expand Up @@ -371,16 +371,16 @@ class FilterChooser;
///
/// An example of a conflict is
///
/// Conflict:
/// 111101000.00........00010000....
/// 111101000.00........0001........
/// 1111010...00........0001........
/// 1111010...00....................
/// 1111010.........................
/// 1111............................
/// ................................
/// VST4q8a 111101000_00________00010000____
/// VST4q8b 111101000_00________00010000____
/// Decoding Conflict:
/// ................................
/// 1111............................
/// 1111010.........................
/// 1111010...00....................
/// 1111010...00........0001........
/// 111101000.00........0001........
/// 111101000.00........00010000....
/// 111101000_00________00010000____ VST4q8a
/// 111101000_00________00010000____ VST4q8b
///
/// The Debug output shows the path that the decoding tree follows to reach the
/// the conclusion that there is a conflict. VST4q8a is a vst4 to double-spaced
Expand Down Expand Up @@ -573,7 +573,7 @@ class FilterChooser {

/// 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, const char *prefix) const;
void dumpStack(raw_ostream &OS, indent Indent) const;

bool PositionFiltered(unsigned Idx) const {
return FilterBitValues[Idx].isSet();
Expand Down Expand Up @@ -692,9 +692,8 @@ void Filter::recurse() {
std::vector<BitValue> BitValueArray(Owner.FilterBitValues);

if (!VariableInstructions.empty()) {
// Conservatively marks each segment position as BIT_UNSET.
for (unsigned bitIndex = 0; bitIndex < NumBits; ++bitIndex)
BitValueArray[StartBit + bitIndex] = BitValue::BIT_UNSET;
BitValueArray[StartBit + bitIndex] = BitValue::BIT_UNFILTERED;

// Delegates to an inferior filter chooser for further processing on this
// group of instructions whose segment values are variable.
Expand Down Expand Up @@ -1131,15 +1130,12 @@ void FilterChooser::dumpFilterArray(raw_ostream &OS,

/// dumpStack - dumpStack traverses the filter chooser chain and calls
/// dumpFilterArray on each filter chooser up to the top level one.
void FilterChooser::dumpStack(raw_ostream &OS, const char *prefix) const {
const FilterChooser *current = this;

while (current) {
OS << prefix;
dumpFilterArray(OS, current->FilterBitValues);
OS << '\n';
current = current->Parent;
}
void FilterChooser::dumpStack(raw_ostream &OS, indent Indent) const {
if (Parent)
Parent->dumpStack(OS, Indent);
OS << Indent;
dumpFilterArray(OS, FilterBitValues);
OS << '\n';
}

// Calculates the island(s) needed to decode the instruction.
Expand Down Expand Up @@ -1778,13 +1774,16 @@ void FilterChooser::doFilter() {
// Print out useful conflict information for postmortem analysis.
errs() << "Decoding Conflict:\n";

dumpStack(errs(), "\t\t");
// Dump filters.
indent Indent(4);
dumpStack(errs(), Indent);

for (auto Opcode : Opcodes) {
// Dump encodings.
for (EncodingIDAndOpcode Opcode : Opcodes) {
const EncodingAndInst &Enc = AllInstructions[Opcode.EncodingID];
errs() << '\t' << Enc << ' ';
dumpBits(errs(), getBitsField(*Enc.EncodingDef, "Inst"));
errs() << '\n';
errs() << Indent;
dumpBits(errs(), getBitsField(*Enc.EncodingDef, "Inst"), BitWidth);
errs() << " " << Enc << '\n';
}
PrintFatalError("Decoding conflict encountered");
}
Expand Down