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[LLVM][TableGen][DecoderEmitter] Add wrapper struct for bit_value_t (#146248)

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Add a convenience wrapper struct for the `bit_value_t` enum type to host
various constructors, query, and printing support. Also refactor related
code in several places. In `getBitsField`, use `llvm::append_range` and
`SmallVector::append()` and eliminate manual loops. Eliminate
`emitNameWithID` and instead use the `operator <<` that does the same
thing as this function. Have `BitValue::getValue()` (replacement for
`Value`) return std::optional<> instead of -1 for unset bits. Terminate
with a fatal error when a decoding conflict is encountered.
This commit is contained in:
Rahul Joshi
2025-07-01 07:36:17 -07:00
committed by GitHub
parent e99da2b7a9
commit d7b8b65e23
2 changed files with 107 additions and 132 deletions
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2
llvm/test/TableGen/FixedLenDecoderEmitter/conflict.td
View File

@@ -1,4 +1,4 @@
// RUN: llvm-tblgen -gen-disassembler -I %p/../../../include %s -o - 2>%t
// RUN: not llvm-tblgen -gen-disassembler -I %p/../../../include %s -o - 2>%t
// RUN: FileCheck %s < %t
include "llvm/Target/Target.td"

237
llvm/utils/TableGen/DecoderEmitter.cpp
View File

@@ -32,6 +32,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MathExtras.h"
@@ -215,13 +216,6 @@ struct EncodingIDAndOpcode {
using EncodingIDsVec = std::vector<EncodingIDAndOpcode>;
using NamespacesHwModesMap = std::map<std::string, std::set<StringRef>>;
raw_ostream &operator<<(raw_ostream &OS, const EncodingAndInst &Value) {
if (Value.EncodingDef != Value.Inst->TheDef)
OS << Value.EncodingDef->getName() << ":";
OS << Value.Inst->TheDef->getName();
return OS;
}
class DecoderEmitter {
const RecordKeeper &RK;
std::vector<EncodingAndInst> NumberedEncodings;
@@ -252,84 +246,96 @@ public:
StringRef PredicateNamespace;
};
} // end anonymous namespace
// The set (BIT_TRUE, BIT_FALSE, BIT_UNSET) represents a ternary logic system
// for a bit value.
//
// BIT_UNFILTERED is used as the init value for a filter position. It is used
// only for filter processings.
typedef enum : uint8_t {
BIT_FALSE, // '0'
BIT_TRUE, // '1'
BIT_UNSET, // '?'
BIT_UNFILTERED // unfiltered
} bit_value_t;
struct BitValue {
enum bit_value_t : uint8_t {
BIT_FALSE, // '0'
BIT_TRUE, // '1'
BIT_UNSET, // '?', printed as '_'
BIT_UNFILTERED // unfiltered, printed as '.'
};
static bool ValueSet(bit_value_t V) {
return (V == BIT_TRUE || V == BIT_FALSE);
}
BitValue(bit_value_t V) : V(V) {}
explicit BitValue(const Init *Init) {
if (const auto *Bit = dyn_cast<BitInit>(Init))
V = Bit->getValue() ? BIT_TRUE : BIT_FALSE;
else
V = BIT_UNSET;
}
BitValue(const BitsInit &Bits, unsigned Idx) : BitValue(Bits.getBit(Idx)) {}
static bool ValueNotSet(bit_value_t V) { return (V == BIT_UNSET); }
bool isSet() const { return V == BIT_TRUE || V == BIT_FALSE; }
bool isUnset() const { return V == BIT_UNSET; }
std::optional<uint64_t> getValue() const {
if (isSet())
return static_cast<uint64_t>(V);
return std::nullopt;
}
static int Value(bit_value_t V) {
return ValueNotSet(V) ? -1 : (V == BIT_FALSE ? 0 : 1);
}
// For printing a bit value.
operator StringRef() const {
switch (V) {
case BIT_FALSE:
return "0";
case BIT_TRUE:
return "1";
case BIT_UNSET:
return "_";
case BIT_UNFILTERED:
return ".";
}
llvm_unreachable("Unknow bit value");
}
static bit_value_t bitFromBits(const BitsInit &bits, unsigned index) {
if (const BitInit *bit = dyn_cast<BitInit>(bits.getBit(index)))
return bit->getValue() ? BIT_TRUE : BIT_FALSE;
bool operator==(bit_value_t Other) const { return Other == V; }
bool operator!=(bit_value_t Other) const { return Other != V; }
// The bit is uninitialized.
return BIT_UNSET;
private:
bit_value_t V;
};
} // end anonymous namespace
static raw_ostream &operator<<(raw_ostream &OS, const EncodingAndInst &Value) {
if (Value.EncodingDef != Value.Inst->TheDef)
OS << Value.EncodingDef->getName() << ":";
OS << Value.Inst->TheDef->getName();
return OS;
}
// Prints the bit value for each position.
static void dumpBits(raw_ostream &OS, const BitsInit &bits) {
for (unsigned index = bits.getNumBits(); index > 0; --index) {
switch (bitFromBits(bits, index - 1)) {
case BIT_TRUE:
OS << "1";
break;
case BIT_FALSE:
OS << "0";
break;
case BIT_UNSET:
OS << "_";
break;
default:
llvm_unreachable("unexpected return value from bitFromBits");
}
}
static void dumpBits(raw_ostream &OS, const BitsInit &Bits) {
for (const Init *Bit : reverse(Bits.getBits()))
OS << BitValue(Bit);
}
static const BitsInit &getBitsField(const Record &def, StringRef str) {
const RecordVal *RV = def.getValue(str);
static const BitsInit &getBitsField(const Record &Def, StringRef FieldName) {
const RecordVal *RV = Def.getValue(FieldName);
if (const BitsInit *Bits = dyn_cast<BitsInit>(RV->getValue()))
return *Bits;
// variable length instruction
VarLenInst VLI = VarLenInst(cast<DagInit>(RV->getValue()), RV);
// Handle variable length instructions.
VarLenInst VLI(cast<DagInit>(RV->getValue()), RV);
SmallVector<const Init *, 16> Bits;
for (const auto &SI : VLI) {
if (const BitsInit *BI = dyn_cast<BitsInit>(SI.Value)) {
for (unsigned Idx = 0U; Idx < BI->getNumBits(); ++Idx) {
Bits.push_back(BI->getBit(Idx));
}
} else if (const BitInit *BI = dyn_cast<BitInit>(SI.Value)) {
if (const BitsInit *BI = dyn_cast<BitsInit>(SI.Value))
llvm::append_range(Bits, BI->getBits());
else if (const BitInit *BI = dyn_cast<BitInit>(SI.Value))
Bits.push_back(BI);
} else {
for (unsigned Idx = 0U; Idx < SI.BitWidth; ++Idx)
Bits.push_back(UnsetInit::get(def.getRecords()));
}
else
Bits.append(SI.BitWidth, UnsetInit::get(Def.getRecords()));
}
return *BitsInit::get(def.getRecords(), Bits);
return *BitsInit::get(Def.getRecords(), Bits);
}
// Representation of the instruction to work on.
typedef std::vector<bit_value_t> insn_t;
typedef std::vector<BitValue> insn_t;
namespace {
@@ -480,7 +486,7 @@ protected:
// Array of bit values passed down from our parent.
// Set to all BIT_UNFILTERED's for Parent == NULL.
std::vector<bit_value_t> FilterBitValues;
std::vector<BitValue> FilterBitValues;
// Links to the FilterChooser above us in the decoding tree.
const FilterChooser *Parent;
@@ -506,15 +512,15 @@ public:
const std::map<unsigned, std::vector<OperandInfo>> &Ops,
unsigned BW, const DecoderEmitter *E)
: AllInstructions(Insts), Opcodes(IDs), Operands(Ops),
FilterBitValues(BW, BIT_UNFILTERED), Parent(nullptr), BestIndex(-1),
BitWidth(BW), Emitter(E) {
FilterBitValues(BW, BitValue::BIT_UNFILTERED), Parent(nullptr),
BestIndex(-1), BitWidth(BW), Emitter(E) {
doFilter();
}
FilterChooser(ArrayRef<EncodingAndInst> Insts,
ArrayRef<EncodingIDAndOpcode> IDs,
const std::map<unsigned, std::vector<OperandInfo>> &Ops,
const std::vector<bit_value_t> &ParentFilterBitValues,
const std::vector<BitValue> &ParentFilterBitValues,
const FilterChooser &parent)
: AllInstructions(Insts), Opcodes(IDs), Operands(Ops),
FilterBitValues(ParentFilterBitValues), Parent(&parent), BestIndex(-1),
@@ -532,7 +538,7 @@ protected:
void insnWithID(insn_t &Insn, unsigned Opcode) const {
const Record *EncodingDef = AllInstructions[Opcode].EncodingDef;
const BitsInit &Bits = getBitsField(*EncodingDef, "Inst");
Insn.resize(std::max(BitWidth, Bits.getNumBits()), BIT_UNSET);
Insn.resize(std::max(BitWidth, Bits.getNumBits()), BitValue::BIT_UNSET);
// We may have a SoftFail bitmask, which specifies a mask where an encoding
// may differ from the value in "Inst" and yet still be valid, but the
// disassembler should return SoftFail instead of Success.
@@ -541,22 +547,13 @@ protected:
const RecordVal *RV = EncodingDef->getValue("SoftFail");
const BitsInit *SFBits = RV ? dyn_cast<BitsInit>(RV->getValue()) : nullptr;
for (unsigned i = 0; i < Bits.getNumBits(); ++i) {
if (SFBits && bitFromBits(*SFBits, i) == BIT_TRUE)
Insn[i] = BIT_UNSET;
if (SFBits && BitValue(*SFBits, i) == BitValue::BIT_TRUE)
Insn[i] = BitValue::BIT_UNSET;
else
Insn[i] = bitFromBits(Bits, i);
Insn[i] = BitValue(Bits, i);
}
}
// Emit the name of the encoding/instruction pair.
void emitNameWithID(raw_ostream &OS, unsigned Opcode) const {
const Record *EncodingDef = AllInstructions[Opcode].EncodingDef;
const Record *InstDef = AllInstructions[Opcode].Inst->TheDef;
if (EncodingDef != InstDef)
OS << EncodingDef->getName() << ":";
OS << InstDef->getName();
}
// Populates the field of the insn given the start position and the number of
// consecutive bits to scan for.
//
@@ -568,7 +565,7 @@ protected:
/// dumpFilterArray - dumpFilterArray prints out debugging info for the given
/// filter array as a series of chars.
void dumpFilterArray(raw_ostream &OS, ArrayRef<bit_value_t> Filter) const;
void dumpFilterArray(raw_ostream &OS, ArrayRef<BitValue> Filter) const;
/// dumpStack - dumpStack traverses the filter chooser chain and calls
/// dumpFilterArray on each filter chooser up to the top level one.
@@ -579,8 +576,8 @@ protected:
return Filters[BestIndex];
}
bool PositionFiltered(unsigned i) const {
return ValueSet(FilterBitValues[i]);
bool PositionFiltered(unsigned Idx) const {
return FilterBitValues[Idx].isSet();
}
// Calculates the island(s) needed to decode the instruction.
@@ -697,12 +694,12 @@ Filter::Filter(const FilterChooser &owner, unsigned startBit, unsigned numBits,
// match the remaining undecoded encoding bits against the singleton.
void Filter::recurse() {
// Starts by inheriting our parent filter chooser's filter bit values.
std::vector<bit_value_t> BitValueArray(Owner.FilterBitValues);
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] = BIT_UNSET;
BitValueArray[StartBit + bitIndex] = BitValue::BIT_UNSET;
// Delegates to an inferior filter chooser for further processing on this
// group of instructions whose segment values are variable.
@@ -723,12 +720,10 @@ 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))
BitValueArray[StartBit + bitIndex] = BIT_TRUE;
else
BitValueArray[StartBit + bitIndex] = BIT_FALSE;
}
for (unsigned bitIndex = 0; bitIndex < NumBits; ++bitIndex)
BitValueArray[StartBit + bitIndex] = Inst.first & (1ULL << bitIndex)
? BitValue::BIT_TRUE
: BitValue::BIT_FALSE;
// Delegates to an inferior filter chooser for further processing on this
// category of instructions.
@@ -1151,10 +1146,10 @@ std::pair<bool, uint64_t> FilterChooser::fieldFromInsn(const insn_t &Insn,
uint64_t Field = 0;
for (unsigned i = 0; i < NumBits; ++i) {
if (Insn[StartBit + i] == BIT_UNSET)
if (Insn[StartBit + i] == BitValue::BIT_UNSET)
return {false, Field};
if (Insn[StartBit + i] == BIT_TRUE)
if (Insn[StartBit + i] == BitValue::BIT_TRUE)
Field = Field | (1ULL << i);
}
@@ -1164,23 +1159,9 @@ 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,
ArrayRef<bit_value_t> Filter) const {
for (unsigned bitIndex = BitWidth; bitIndex > 0; bitIndex--) {
switch (Filter[bitIndex - 1]) {
case BIT_UNFILTERED:
OS << ".";
break;
case BIT_UNSET:
OS << "_";
break;
case BIT_TRUE:
OS << "1";
break;
case BIT_FALSE:
OS << "0";
break;
}
}
ArrayRef<BitValue> Filter) const {
for (unsigned bitIndex = BitWidth; bitIndex > 0; bitIndex--)
OS << Filter[bitIndex - 1];
}
/// dumpStack - dumpStack traverses the filter chooser chain and calls
@@ -1211,28 +1192,28 @@ unsigned FilterChooser::getIslands(std::vector<Island> &Islands,
unsigned State = 0;
for (unsigned i = 0; i < BitWidth; ++i) {
int64_t Val = Value(Insn[i]);
std::optional<uint64_t> Val = Insn[i].getValue();
bool Filtered = PositionFiltered(i);
switch (State) {
default:
llvm_unreachable("Unreachable code!");
case 0:
case 1:
if (Filtered || Val == -1) {
if (Filtered || !Val) {
State = 1; // Still in Water
} else {
State = 2; // Into the Island
StartBit = i;
FieldVal = Val;
FieldVal = *Val;
}
break;
case 2:
if (Filtered || Val == -1) {
if (Filtered || !Val) {
State = 1; // Into the Water
Islands.push_back({StartBit, i - StartBit, FieldVal});
} else {
State = 2; // Still in Island
FieldVal |= Val << (i - StartBit);
FieldVal |= *Val << (i - StartBit);
}
break;
}
@@ -1453,22 +1434,19 @@ void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
APInt PositiveMask(BitWidth, 0ULL);
APInt NegativeMask(BitWidth, 0ULL);
for (unsigned i = 0; i < BitWidth; ++i) {
bit_value_t B = bitFromBits(*SFBits, i);
bit_value_t IB = bitFromBits(*InstBits, i);
BitValue B(*SFBits, i);
BitValue IB(*InstBits, i);
if (B != BIT_TRUE)
if (B != BitValue::BIT_TRUE)
continue;
switch (IB) {
case BIT_FALSE:
if (IB == BitValue::BIT_FALSE) {
// The bit is meant to be false, so emit a check to see if it is true.
PositiveMask.setBit(i);
break;
case BIT_TRUE:
} else if (IB == BitValue::BIT_TRUE) {
// The bit is meant to be true, so emit a check to see if it is false.
NegativeMask.setBit(i);
break;
default:
} else {
// The bit is not set; this must be an error!
errs() << "SoftFail Conflict: bit SoftFail{" << i << "} in "
<< AllInstructions[Opc] << " is set but Inst{" << i
@@ -1651,8 +1629,7 @@ bool FilterChooser::filterProcessor(bool AllowMixed, bool Greedy) {
// FILTERED bit positions provide no entropy and are not worthy of pursuing.
// Filter::recurse() set either BIT_TRUE or BIT_FALSE for each position.
for (BitIndex = 0; BitIndex < BitWidth; ++BitIndex)
if (FilterBitValues[BitIndex] == BIT_TRUE ||
FilterBitValues[BitIndex] == BIT_FALSE)
if (FilterBitValues[BitIndex].isSet())
bitAttrs[BitIndex] = ATTR_FILTERED;
for (const auto &OpcPair : Opcodes) {
@@ -1663,17 +1640,17 @@ bool FilterChooser::filterProcessor(bool AllowMixed, bool Greedy) {
for (BitIndex = 0; BitIndex < BitWidth; ++BitIndex) {
switch (bitAttrs[BitIndex]) {
case ATTR_NONE:
if (insn[BitIndex] == BIT_UNSET)
if (insn[BitIndex] == BitValue::BIT_UNSET)
bitAttrs[BitIndex] = ATTR_ALL_UNSET;
else
bitAttrs[BitIndex] = ATTR_ALL_SET;
break;
case ATTR_ALL_SET:
if (insn[BitIndex] == BIT_UNSET)
if (insn[BitIndex] == BitValue::BIT_UNSET)
bitAttrs[BitIndex] = ATTR_MIXED;
break;
case ATTR_ALL_UNSET:
if (insn[BitIndex] != BIT_UNSET)
if (insn[BitIndex] != BitValue::BIT_UNSET)
bitAttrs[BitIndex] = ATTR_MIXED;
break;
case ATTR_MIXED:
@@ -1868,7 +1845,7 @@ void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
return;
}
// We don't know how to decode these instructions! Dump the
// We don't know how to decode these instructions! Dump the
// conflict set and bail.
// Print out useful conflict information for postmortem analysis.
@@ -1877,14 +1854,12 @@ void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
dumpStack(errs(), "\t\t");
for (auto Opcode : Opcodes) {
errs() << '\t';
emitNameWithID(errs(), Opcode.EncodingID);
errs() << " ";
dumpBits(
errs(),
getBitsField(*AllInstructions[Opcode.EncodingID].EncodingDef, "Inst"));
const EncodingAndInst &Enc = AllInstructions[Opcode.EncodingID];
errs() << '\t' << Enc << ' ';
dumpBits(errs(), getBitsField(*Enc.EncodingDef, "Inst"));
errs() << '\n';
}
PrintFatalError("Decoding conflict encountered");
}
static std::string findOperandDecoderMethod(const Record *Record) {