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llvm-project/llvm/utils/TableGen/DecoderEmitter.cpp
Sergei Barannikov 6a7ade03d1
[TableGen][DecoderEmitter] Remove redundant variable (NFC) (#154880) 
`NumFiltered` is the number of elements in all vectors in a map.
It is ever compared to 1, which is equivalent to checking if the map
contains exactly one vector with exactly one element.
2025-08-22 04:42:06 +00:00

2574 lines
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//===---------------- DecoderEmitter.cpp - Decoder Generator --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// It contains the tablegen backend that emits the decoder functions for
// targets with fixed/variable length instruction set.
//
//===----------------------------------------------------------------------===//
#include "Common/CodeGenHwModes.h"
#include "Common/CodeGenInstruction.h"
#include "Common/CodeGenTarget.h"
#include "Common/InfoByHwMode.h"
#include "Common/VarLenCodeEmitterGen.h"
#include "TableGenBackends.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/CachedHashString.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCDecoderOps.h"
#include "llvm/Support/Casting.h"
#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/KnownBits.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TableGen/Error.h"
#include "llvm/TableGen/Record.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "decoder-emitter"
extern cl::OptionCategory DisassemblerEmitterCat;
enum SuppressLevel {
SUPPRESSION_DISABLE,
SUPPRESSION_LEVEL1,
SUPPRESSION_LEVEL2
};
static cl::opt<SuppressLevel> DecoderEmitterSuppressDuplicates(
"suppress-per-hwmode-duplicates",
cl::desc("Suppress duplication of instrs into per-HwMode decoder tables"),
cl::values(
clEnumValN(
SUPPRESSION_DISABLE, "O0",
"Do not prevent DecoderTable duplications caused by HwModes"),
clEnumValN(
SUPPRESSION_LEVEL1, "O1",
"Remove duplicate DecoderTable entries generated due to HwModes"),
clEnumValN(
SUPPRESSION_LEVEL2, "O2",
"Extract HwModes-specific instructions into new DecoderTables, "
"significantly reducing Table Duplications")),
cl::init(SUPPRESSION_DISABLE), cl::cat(DisassemblerEmitterCat));
static cl::opt<bool> LargeTable(
"large-decoder-table",
cl::desc("Use large decoder table format. This uses 24 bits for offset\n"
"in the table instead of the default 16 bits."),
cl::init(false), cl::cat(DisassemblerEmitterCat));
static cl::opt<bool> UseFnTableInDecodeToMCInst(
"use-fn-table-in-decode-to-mcinst",
cl::desc(
"Use a table of function pointers instead of a switch case in the\n"
"generated `decodeToMCInst` function. Helps improve compile time\n"
"of the generated code."),
cl::init(false), cl::cat(DisassemblerEmitterCat));
STATISTIC(NumEncodings, "Number of encodings considered");
STATISTIC(NumEncodingsLackingDisasm,
"Number of encodings without disassembler info");
STATISTIC(NumInstructions, "Number of instructions considered");
STATISTIC(NumEncodingsSupported, "Number of encodings supported");
STATISTIC(NumEncodingsOmitted, "Number of encodings omitted");
static unsigned getNumToSkipInBytes() { return LargeTable ? 3 : 2; }
/// Similar to KnownBits::print(), but allows you to specify a character to use
/// to print unknown bits.
static void printKnownBits(raw_ostream &OS, const KnownBits &Bits,
char Unknown) {
for (unsigned I = Bits.getBitWidth(); I--;) {
if (Bits.Zero[I] && Bits.One[I])
OS << '!';
else if (Bits.Zero[I])
OS << '0';
else if (Bits.One[I])
OS << '1';
else
OS << Unknown;
}
}
namespace {
struct EncodingField {
unsigned Base, Width, Offset;
EncodingField(unsigned B, unsigned W, unsigned O)
: Base(B), Width(W), Offset(O) {}
};
struct OperandInfo {
std::vector<EncodingField> Fields;
std::string Decoder;
bool HasCompleteDecoder;
uint64_t InitValue = 0;
OperandInfo(std::string D, bool HCD) : Decoder(D), HasCompleteDecoder(HCD) {}
void addField(unsigned Base, unsigned Width, unsigned Offset) {
Fields.push_back(EncodingField(Base, Width, Offset));
}
unsigned numFields() const { return Fields.size(); }
typedef std::vector<EncodingField>::const_iterator const_iterator;
const_iterator begin() const { return Fields.begin(); }
const_iterator end() const { return Fields.end(); }
};
/// Represents a parsed InstructionEncoding record or a record derived from it.
class InstructionEncoding {
/// The Record this encoding originates from.
const Record *EncodingDef;
/// The instruction this encoding is for.
const CodeGenInstruction *Inst;
/// The name of this encoding (for debugging purposes).
std::string Name;
/// Known bits of this encoding. This is the value of the `Inst` field
/// with any variable references replaced with '?'.
KnownBits InstBits;
/// Mask of bits that should be considered unknown during decoding.
/// This is the value of the `SoftFail` field.
APInt SoftFailBits;
/// The name of the function to use for decoding. May be an empty string,
/// meaning the decoder is generated.
StringRef DecoderMethod;
/// Whether the custom decoding function always succeeds. If a custom decoder
/// function is specified, the value is taken from the target description,
/// otherwise it is inferred.
bool HasCompleteDecoder;
/// Information about the operands' contribution to this encoding.
SmallVector<OperandInfo, 16> Operands;
public:
InstructionEncoding(const Record *EncodingDef,
const CodeGenInstruction *Inst);
/// Returns the Record this encoding originates from.
const Record *getRecord() const { return EncodingDef; }
/// Returns the instruction this encoding is for.
const CodeGenInstruction *getInstruction() const { return Inst; }
/// Returns the name of this encoding, for debugging purposes.
StringRef getName() const { return Name; }
/// Returns the size of this encoding, in bits.
unsigned getBitWidth() const { return InstBits.getBitWidth(); }
/// Returns the known bits of this encoding.
const KnownBits &getInstBits() const { return InstBits; }
/// Returns a mask of bits that should be considered unknown during decoding.
const APInt &getSoftFailBits() const { return SoftFailBits; }
/// Returns the name of the function to use for decoding, or an empty string
/// if the decoder is generated.
StringRef getDecoderMethod() const { return DecoderMethod; }
/// Returns whether the decoder (either generated or specified by the user)
/// always succeeds.
bool hasCompleteDecoder() const { return HasCompleteDecoder; }
/// Returns information about the operands' contribution to this encoding.
ArrayRef<OperandInfo> getOperands() const { return Operands; }
private:
void parseVarLenEncoding(const VarLenInst &VLI);
void parseFixedLenEncoding(const BitsInit &Bits);
void parseVarLenOperands(const VarLenInst &VLI);
void parseFixedLenOperands(const BitsInit &Bits);
};
typedef std::vector<uint32_t> FixupList;
typedef std::vector<FixupList> FixupScopeList;
typedef SmallSetVector<CachedHashString, 16> PredicateSet;
typedef SmallSetVector<CachedHashString, 16> DecoderSet;
class DecoderTable {
public:
DecoderTable() { Data.reserve(16384); }
void clear() { Data.clear(); }
void push_back(uint8_t Item) { Data.push_back(Item); }
size_t size() const { return Data.size(); }
const uint8_t *data() const { return Data.data(); }
using const_iterator = std::vector<uint8_t>::const_iterator;
const_iterator begin() const { return Data.begin(); }
const_iterator end() const { return Data.end(); }
// 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);
Data.insert(Data.end(), Buffer, Buffer + Len);
}
// Insert space for `NumToSkip` and return the position
// in the table for patching.
size_t insertNumToSkip() {
size_t Size = Data.size();
Data.insert(Data.end(), getNumToSkipInBytes(), 0);
return Size;
}
void patchNumToSkip(size_t FixupIdx, uint32_t DestIdx) {
// Calculate the distance from the byte following the fixup entry byte
// to the destination. The Target is calculated from after the
// `getNumToSkipInBytes()`-byte NumToSkip entry itself, so subtract
// `getNumToSkipInBytes()` from the displacement here to account for that.
assert(DestIdx >= FixupIdx + getNumToSkipInBytes() &&
"Expecting a forward jump in the decoding table");
uint32_t Delta = DestIdx - FixupIdx - getNumToSkipInBytes();
if (!isUIntN(8 * getNumToSkipInBytes(), Delta))
PrintFatalError(
"disassembler decoding table too large, try --large-decoder-table");
Data[FixupIdx] = static_cast<uint8_t>(Delta);
Data[FixupIdx + 1] = static_cast<uint8_t>(Delta >> 8);
if (getNumToSkipInBytes() == 3)
Data[FixupIdx + 2] = static_cast<uint8_t>(Delta >> 16);
}
private:
std::vector<uint8_t> Data;
};
struct DecoderTableInfo {
DecoderTable Table;
FixupScopeList FixupStack;
PredicateSet Predicates;
DecoderSet Decoders;
bool isOutermostScope() const { return FixupStack.size() == 1; }
void pushScope() { FixupStack.emplace_back(); }
void popScope() {
// Resolve any remaining fixups in the current scope before popping it.
// All fixups resolve to the current location.
uint32_t DestIdx = Table.size();
for (uint32_t FixupIdx : FixupStack.back())
Table.patchNumToSkip(FixupIdx, DestIdx);
FixupStack.pop_back();
}
};
using NamespacesHwModesMap = std::map<std::string, std::set<unsigned>>;
class DecoderEmitter {
const RecordKeeper &RK;
CodeGenTarget Target;
const CodeGenHwModes &CGH;
/// All parsed encodings.
std::vector<InstructionEncoding> Encodings;
/// Encodings IDs for each HwMode. An ID is an index into Encodings.
SmallDenseMap<unsigned, std::vector<unsigned>> EncodingIDsByHwMode;
public:
DecoderEmitter(const RecordKeeper &RK, StringRef PredicateNamespace);
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;
void emitInstrLenTable(formatted_raw_ostream &OS,
ArrayRef<unsigned> InstrLen) const;
void emitPredicateFunction(formatted_raw_ostream &OS,
PredicateSet &Predicates) const;
void emitDecoderFunction(formatted_raw_ostream &OS,
DecoderSet &Decoders) const;
// run - Output the code emitter
void run(raw_ostream &o) const;
private:
void collectHwModesReferencedForEncodings(
std::vector<unsigned> &HwModeIDs,
NamespacesHwModesMap &NamespacesWithHwModes) const;
void
handleHwModesUnrelatedEncodings(unsigned EncodingID,
ArrayRef<unsigned> HwModeIDs,
NamespacesHwModesMap &NamespacesWithHwModes);
void parseInstructionEncodings();
public:
StringRef PredicateNamespace;
};
} // end anonymous namespace
namespace {
class FilterChooser;
/// Filter - Filter works with FilterChooser to produce the decoding tree for
/// the ISA.
///
/// It is useful to think of a Filter as governing the switch stmts of the
/// decoding tree in a certain level. Each case stmt delegates to an inferior
/// FilterChooser to decide what further decoding logic to employ, or in another
/// words, what other remaining bits to look at. The FilterChooser eventually
/// chooses a best Filter to do its job.
///
/// This recursive scheme ends when the number of Opcodes assigned to the
/// FilterChooser becomes 1 or if there is a conflict. A conflict happens when
/// the Filter/FilterChooser combo does not know how to distinguish among the
/// Opcodes assigned.
///
/// An example of a conflict is
///
/// 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
/// even registers, while VST4q8b is a vst4 to double-spaced odd registers.
///
/// The encoding info in the .td files does not specify this meta information,
/// which could have been used by the decoder to resolve the conflict. The
/// decoder could try to decode the even/odd register numbering and assign to
/// VST4q8a or VST4q8b, but for the time being, the decoder chooses the "a"
/// version and return the Opcode since the two have the same Asm format string.
class Filter {
protected:
const FilterChooser &Owner; // FilterChooser who owns this filter
unsigned StartBit; // the starting bit position
unsigned NumBits; // number of bits to filter
// Map of well-known segment value to the set of uid's with that value.
std::map<uint64_t, std::vector<unsigned>> FilteredIDs;
// Set of uid's with non-constant segment values.
std::vector<unsigned> VariableIDs;
// Map of well-known segment value to its delegate.
std::map<uint64_t, std::unique_ptr<const FilterChooser>> FilterChooserMap;
// A filter chooser for encodings that contain some '?' in the filtered range.
std::unique_ptr<const FilterChooser> VariableFC;
public:
Filter(Filter &&f);
Filter(const FilterChooser &owner, unsigned startBit, unsigned numBits);
~Filter() = default;
bool hasSingleFilteredID() const {
return FilteredIDs.size() == 1 && FilteredIDs.begin()->second.size() == 1;
}
unsigned getSingletonEncodingID() const {
assert(hasSingleFilteredID());
return FilteredIDs.begin()->second.front();
}
// Return the filter chooser for the group of instructions without constant
// segment values.
const FilterChooser &getVariableFC() const {
assert(hasSingleFilteredID() && FilterChooserMap.empty());
return *VariableFC;
}
// Divides the decoding task into sub tasks and delegates them to the
// inferior FilterChooser's.
//
// A special case arises when there's only one entry in the filtered
// instructions. In order to unambiguously decode the singleton, we need to
// match the remaining undecoded encoding bits against the singleton.
void recurse();
// Emit table entries to decode instructions given a segment or segments of
// bits.
void emitTableEntry(DecoderTableInfo &TableInfo) const;
// Returns the number of fanout produced by the filter. More fanout implies
// the filter distinguishes more categories of instructions.
unsigned usefulness() const;
}; // end class Filter
// These are states of our finite state machines used in FilterChooser's
// filterProcessor() which produces the filter candidates to use.
enum bitAttr_t {
ATTR_NONE,
ATTR_FILTERED,
ATTR_ALL_SET,
ATTR_ALL_UNSET,
ATTR_MIXED
};
/// FilterChooser - FilterChooser chooses the best filter among a set of Filters
/// in order to perform the decoding of instructions at the current level.
///
/// Decoding proceeds from the top down. Based on the well-known encoding bits
/// of instructions available, FilterChooser builds up the possible Filters that
/// can further the task of decoding by distinguishing among the remaining
/// candidate instructions.
///
/// Once a filter has been chosen, it is called upon to divide the decoding task
/// into sub-tasks and delegates them to its inferior FilterChoosers for further
/// processings.
///
/// 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.
class FilterChooser {
protected:
friend class Filter;
// Vector of encodings to choose our filter.
ArrayRef<InstructionEncoding> Encodings;
// Vector of encoding IDs for this filter chooser to work on.
ArrayRef<unsigned> EncodingIDs;
// The selected filter, if any.
std::unique_ptr<Filter> BestFilter;
// Array of bit values passed down from our parent.
// Set to all unknown for Parent == nullptr.
KnownBits FilterBits;
// Links to the FilterChooser above us in the decoding tree.
const FilterChooser *Parent;
// Width of instructions
unsigned BitWidth;
// Parent emitter
const DecoderEmitter *Emitter;
struct Island {
unsigned StartBit;
unsigned NumBits;
uint64_t FieldVal;
};
public:
FilterChooser(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs, unsigned BW,
const DecoderEmitter *E)
: Encodings(Encodings), EncodingIDs(EncodingIDs), FilterBits(BW),
Parent(nullptr), BitWidth(BW), Emitter(E) {
doFilter();
}
FilterChooser(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs,
const KnownBits &ParentFilterBits, const FilterChooser &parent)
: Encodings(Encodings), EncodingIDs(EncodingIDs),
FilterBits(ParentFilterBits), Parent(&parent),
BitWidth(parent.BitWidth), Emitter(parent.Emitter) {
assert(!FilterBits.hasConflict() && "Broken filter");
doFilter();
}
FilterChooser(const FilterChooser &) = delete;
void operator=(const FilterChooser &) = delete;
unsigned getBitWidth() const { return BitWidth; }
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();
// Truncate or extend with unknown bits according to the filter bit width.
// FIXME: We should stop doing this.
return EncodingBits.anyextOrTrunc(BitWidth);
}
/// 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) const;
bool isPositionFiltered(unsigned Idx) const {
return FilterBits.Zero[Idx] || FilterBits.One[Idx];
}
// Calculates the island(s) needed to decode the instruction.
// This returns a list of undecoded bits of an instructions, for example,
// Inst{20} = 1 && Inst{3-0} == 0b1111 represents two islands of yet-to-be
// decoded bits in order to verify that the instruction matches the Opcode.
std::vector<Island> getIslands(const KnownBits &EncodingBits) const;
// Emits code to check the Predicates member of an instruction are true.
// Returns true if predicate matches were emitted, false otherwise.
bool emitPredicateMatch(raw_ostream &OS, unsigned EncodingID) const;
bool emitPredicateMatchAux(const Init &Val, bool ParenIfBinOp,
raw_ostream &OS) const;
bool doesOpcodeNeedPredicate(unsigned EncodingID) const;
unsigned getPredicateIndex(DecoderTableInfo &TableInfo, StringRef P) const;
void emitPredicateTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const;
void emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const;
// Emits table entries to decode the singleton.
void emitSingletonTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const;
// Emits code to decode the singleton, and then to decode the rest.
void emitSingletonTableEntry(DecoderTableInfo &TableInfo,
const Filter &Best) const;
void emitBinaryParser(raw_ostream &OS, indent Indent,
const OperandInfo &OpInfo) const;
void emitDecoder(raw_ostream &OS, indent Indent, unsigned EncodingID) const;
unsigned getDecoderIndex(DecoderSet &Decoders, unsigned EncodingID) const;
// Assign a single filter and run with it.
void runSingleFilter(unsigned startBit, unsigned numBit);
// reportRegion is a helper function for filterProcessor to mark a region as
// eligible for use as a filter region.
void reportRegion(std::vector<std::unique_ptr<Filter>> &Filters, bitAttr_t RA,
unsigned StartBit, unsigned BitIndex, bool AllowMixed);
// FilterProcessor scans the well-known encoding bits of the instructions and
// builds up a list of candidate filters. It chooses the best filter and
// recursively descends down the decoding tree.
bool filterProcessor(ArrayRef<bitAttr_t> BitAttrs, bool AllowMixed,
bool Greedy = true);
// Decides on the best configuration of filter(s) to use in order to decode
// the instructions. A conflict of instructions may occur, in which case we
// dump the conflict set to the standard error.
void doFilter();
public:
// emitTableEntries - Emit state machine entries to decode our share of
// instructions.
void emitTableEntries(DecoderTableInfo &TableInfo) const;
};
} // end anonymous namespace
///////////////////////////
// //
// Filter Implementation //
// //
///////////////////////////
Filter::Filter(Filter &&f)
: Owner(f.Owner), StartBit(f.StartBit), NumBits(f.NumBits),
FilteredIDs(std::move(f.FilteredIDs)),
VariableIDs(std::move(f.VariableIDs)),
FilterChooserMap(std::move(f.FilterChooserMap)),
VariableFC(std::move(f.VariableFC)) {}
Filter::Filter(const FilterChooser &owner, unsigned startBit, unsigned numBits)
: Owner(owner), StartBit(startBit), NumBits(numBits) {
assert(StartBit + NumBits - 1 < Owner.BitWidth);
for (unsigned EncodingID : Owner.EncodingIDs) {
// Populates the insn given the uid.
KnownBits EncodingBits = Owner.getMandatoryEncodingBits(EncodingID);
// Scans the segment for possibly well-specified encoding bits.
KnownBits FieldBits = EncodingBits.extractBits(NumBits, StartBit);
if (FieldBits.isConstant()) {
// The encoding bits are well-known. Lets add the uid of the
// instruction into the bucket keyed off the constant field value.
FilteredIDs[FieldBits.getConstant().getZExtValue()].push_back(EncodingID);
} else {
// Some of the encoding bit(s) are unspecified. This contributes to
// one additional member of "Variable" instructions.
VariableIDs.push_back(EncodingID);
}
}
assert((FilteredIDs.size() + VariableIDs.size() > 0) &&
"Filter returns no instruction categories");
}
// Divides the decoding task into sub tasks and delegates them to the
// inferior FilterChooser's.
//
// A special case arises when there's only one entry in the filtered
// instructions. In order to unambiguously decode the singleton, we need to
// match the remaining undecoded encoding bits against the singleton.
void Filter::recurse() {
// Starts by inheriting our parent filter chooser's filter bit values.
KnownBits FilterBits = Owner.FilterBits;
assert(FilterBits.extractBits(NumBits, StartBit).isUnknown());
if (!VariableIDs.empty()) {
// Delegates to an inferior filter chooser for further processing on this
// group of instructions whose segment values are variable.
VariableFC = std::make_unique<FilterChooser>(Owner.Encodings, VariableIDs,
FilterBits, Owner);
}
// No need to recurse for a singleton filtered instruction.
// See also Filter::emit*().
if (hasSingleFilteredID()) {
assert(VariableFC && "Shouldn't have created a filter for one encoding!");
return;
}
// Otherwise, create sub choosers.
for (const auto &[FilterVal, EncodingIDs] : FilteredIDs) {
// Create a new filter by inserting the field bits into the parent filter.
APInt FieldBits(NumBits, FilterVal);
FilterBits.insertBits(KnownBits::makeConstant(FieldBits), StartBit);
// Delegates to an inferior filter chooser for further processing on this
// category of instructions.
FilterChooserMap.try_emplace(
FilterVal, std::make_unique<FilterChooser>(Owner.Encodings, EncodingIDs,
FilterBits, Owner));
}
}
// Emit table entries to decode instructions given a segment or segments
// of bits.
void Filter::emitTableEntry(DecoderTableInfo &TableInfo) const {
assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
TableInfo.Table.push_back(MCD::OPC_ExtractField);
TableInfo.Table.insertULEB128(StartBit);
TableInfo.Table.push_back(NumBits);
// If VariableFC is present, we need to add a new scope for this filter.
// Otherwise, we can skip adding a new scope and any patching added will
// automatically be added to the enclosing scope.
const uint64_t LastFilter = FilterChooserMap.rbegin()->first;
if (VariableFC)
TableInfo.FixupStack.emplace_back();
DecoderTable &Table = TableInfo.Table;
size_t PrevFilter = 0;
for (const auto &[FilterVal, Delegate] : FilterChooserMap) {
// The last filtervalue emitted can be OPC_FilterValue if we are at
// outermost scope.
const uint8_t DecoderOp =
FilterVal == LastFilter && TableInfo.isOutermostScope()
? MCD::OPC_FilterValueOrFail
: MCD::OPC_FilterValue;
Table.push_back(DecoderOp);
Table.insertULEB128(FilterVal);
if (DecoderOp == MCD::OPC_FilterValue) {
// Reserve space for the NumToSkip entry. We'll backpatch the value later.
PrevFilter = Table.insertNumToSkip();
} else {
PrevFilter = 0;
}
// We arrive at a category of instructions with the same segment value.
// Now delegate to the sub filter chooser for further decodings.
// The case may fallthrough, which happens if the remaining well-known
// encoding bits do not match exactly.
Delegate->emitTableEntries(TableInfo);
// Now that we've emitted the body of the handler, update the NumToSkip
// of the filter itself to be able to skip forward when false.
if (PrevFilter)
Table.patchNumToSkip(PrevFilter, Table.size());
}
if (VariableFC) {
// Each scope should always have at least one filter value to check for.
assert(PrevFilter != 0 && "empty filter set!");
TableInfo.popScope();
PrevFilter = 0; // Don't re-process the filter's fallthrough.
// Delegate to the sub filter chooser for further decoding.
VariableFC->emitTableEntries(TableInfo);
}
// If there is no fallthrough and the final filter was not in the outermost
// scope, then it must be fixed up according to the enclosing scope rather
// than the current position.
if (PrevFilter)
TableInfo.FixupStack.back().push_back(PrevFilter);
}
// Returns the number of fanout produced by the filter. More fanout implies
// the filter distinguishes more categories of instructions.
unsigned Filter::usefulness() const {
return FilteredIDs.size() + VariableIDs.empty();
}
//////////////////////////////////
// //
// Filterchooser Implementation //
// //
//////////////////////////////////
// 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 {
// 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.
DenseMap<unsigned, unsigned> OpcodeToEncodingID;
OpcodeToEncodingID.reserve(EncodingIDs.size());
for (unsigned EncodingID : EncodingIDs) {
const Record *InstDef = Encodings[EncodingID].getInstruction()->TheDef;
OpcodeToEncodingID[Target.getInstrIntValue(InstDef)] = EncodingID;
}
OS << "static const uint8_t DecoderTable" << Namespace;
if (HwModeID != DefaultMode)
OS << '_' << Target.getHwModes().getModeName(HwModeID);
OS << BitWidth << "[] = {\n";
// Emit ULEB128 encoded value to OS, returning the number of bytes emitted.
auto emitULEB128 = [](DecoderTable::const_iterator &I,
formatted_raw_ostream &OS) {
while (*I >= 128)
OS << (unsigned)*I++ << ", ";
OS << (unsigned)*I++ << ", ";
};
// Emit `getNumToSkipInBytes()`-byte numtoskip value to OS, returning the
// NumToSkip value.
auto emitNumToSkip = [](DecoderTable::const_iterator &I,
formatted_raw_ostream &OS) {
uint8_t Byte = *I++;
uint32_t NumToSkip = Byte;
OS << (unsigned)Byte << ", ";
Byte = *I++;
OS << (unsigned)Byte << ", ";
NumToSkip |= Byte << 8;
if (getNumToSkipInBytes() == 3) {
Byte = *I++;
OS << (unsigned)(Byte) << ", ";
NumToSkip |= Byte << 16;
}
return NumToSkip;
};
// FIXME: We may be able to use the NumToSkip values to recover
// appropriate indentation levels.
DecoderTable::const_iterator I = Table.begin();
DecoderTable::const_iterator E = Table.end();
const uint8_t *const EndPtr = Table.data() + Table.size();
auto emitNumToSkipComment = [&](uint32_t NumToSkip, bool InComment = false) {
uint32_t Index = ((I - Table.begin()) + NumToSkip);
OS << (InComment ? ", " : "// ");
OS << "Skip to: " << Index;
if (*(I + NumToSkip) == MCD::OPC_Fail)
OS << " (Fail)";
};
unsigned OpcodeMask = 0;
while (I != E) {
assert(I < E && "incomplete decode table entry!");
uint64_t Pos = I - Table.begin();
OS << "/* " << Pos << " */";
OS.PadToColumn(12);
const uint8_t DecoderOp = *I++;
OpcodeMask |= (1 << DecoderOp);
switch (DecoderOp) {
default:
PrintFatalError("Invalid decode table opcode: " + Twine((int)DecoderOp) +
" at index " + Twine(Pos));
case MCD::OPC_ExtractField: {
OS << " MCD::OPC_ExtractField, ";
// ULEB128 encoded start value.
const char *ErrMsg = nullptr;
unsigned Start = decodeULEB128(&*I, nullptr, EndPtr, &ErrMsg);
assert(ErrMsg == nullptr && "ULEB128 value too large!");
emitULEB128(I, OS);
unsigned Len = *I++;
OS << Len << ", // Inst{";
if (Len > 1)
OS << (Start + Len - 1) << "-";
OS << Start << "} ...\n";
break;
}
case MCD::OPC_FilterValue:
case MCD::OPC_FilterValueOrFail: {
bool IsFail = DecoderOp == MCD::OPC_FilterValueOrFail;
OS << " MCD::OPC_FilterValue" << (IsFail ? "OrFail, " : ", ");
// The filter value is ULEB128 encoded.
emitULEB128(I, OS);
if (!IsFail) {
uint32_t NumToSkip = emitNumToSkip(I, OS);
emitNumToSkipComment(NumToSkip);
}
OS << '\n';
break;
}
case MCD::OPC_CheckField:
case MCD::OPC_CheckFieldOrFail: {
bool IsFail = DecoderOp == MCD::OPC_CheckFieldOrFail;
OS << " MCD::OPC_CheckField" << (IsFail ? "OrFail, " : ", ");
// ULEB128 encoded start value.
emitULEB128(I, OS);
// 8-bit length.
unsigned Len = *I++;
OS << Len << ", ";
// ULEB128 encoded field value.
emitULEB128(I, OS);
if (!IsFail) {
uint32_t NumToSkip = emitNumToSkip(I, OS);
emitNumToSkipComment(NumToSkip);
}
OS << '\n';
break;
}
case MCD::OPC_CheckPredicate:
case MCD::OPC_CheckPredicateOrFail: {
bool IsFail = DecoderOp == MCD::OPC_CheckPredicateOrFail;
OS << " MCD::OPC_CheckPredicate" << (IsFail ? "OrFail, " : ", ");
emitULEB128(I, OS);
if (!IsFail) {
uint32_t NumToSkip = emitNumToSkip(I, OS);
emitNumToSkipComment(NumToSkip);
}
OS << '\n';
break;
}
case MCD::OPC_Decode:
case MCD::OPC_TryDecode:
case MCD::OPC_TryDecodeOrFail: {
bool IsFail = DecoderOp == MCD::OPC_TryDecodeOrFail;
bool IsTry = DecoderOp == MCD::OPC_TryDecode || IsFail;
// Decode the Opcode value.
const char *ErrMsg = nullptr;
unsigned Opc = decodeULEB128(&*I, nullptr, EndPtr, &ErrMsg);
assert(ErrMsg == nullptr && "ULEB128 value too large!");
OS << " MCD::OPC_" << (IsTry ? "Try" : "") << "Decode"
<< (IsFail ? "OrFail, " : ", ");
emitULEB128(I, OS);
// Decoder index.
unsigned DecodeIdx = decodeULEB128(&*I, nullptr, EndPtr, &ErrMsg);
assert(ErrMsg == nullptr && "ULEB128 value too large!");
emitULEB128(I, OS);
auto EncI = OpcodeToEncodingID.find(Opc);
assert(EncI != OpcodeToEncodingID.end() && "no encoding entry");
auto EncodingID = EncI->second;
if (!IsTry) {
OS << "// Opcode: " << Encodings[EncodingID].getName()
<< ", DecodeIdx: " << DecodeIdx << '\n';
break;
}
// Fallthrough for OPC_TryDecode.
if (!IsFail) {
uint32_t NumToSkip = emitNumToSkip(I, OS);
OS << "// Opcode: " << Encodings[EncodingID].getName()
<< ", DecodeIdx: " << DecodeIdx;
emitNumToSkipComment(NumToSkip, /*InComment=*/true);
}
OS << '\n';
break;
}
case MCD::OPC_SoftFail: {
OS << " MCD::OPC_SoftFail, ";
// Decode the positive mask.
const char *ErrMsg = nullptr;
uint64_t PositiveMask = decodeULEB128(&*I, nullptr, EndPtr, &ErrMsg);
assert(ErrMsg == nullptr && "ULEB128 value too large!");
emitULEB128(I, OS);
// Decode the negative mask.
uint64_t NegativeMask = decodeULEB128(&*I, nullptr, EndPtr, &ErrMsg);
assert(ErrMsg == nullptr && "ULEB128 value too large!");
emitULEB128(I, OS);
OS << "// +ve mask: 0x";
OS.write_hex(PositiveMask);
OS << ", -ve mask: 0x";
OS.write_hex(NegativeMask);
OS << '\n';
break;
}
case MCD::OPC_Fail:
OS << " MCD::OPC_Fail,\n";
break;
}
}
OS << " 0\n";
OS << "};\n\n";
return OpcodeMask;
}
void DecoderEmitter::emitInstrLenTable(formatted_raw_ostream &OS,
ArrayRef<unsigned> InstrLen) const {
OS << "static const uint8_t InstrLenTable[] = {\n";
for (unsigned Len : InstrLen)
OS << Len << ",\n";
OS << "};\n\n";
}
void DecoderEmitter::emitPredicateFunction(formatted_raw_ostream &OS,
PredicateSet &Predicates) const {
// The predicate function is just a big switch statement based on the
// input predicate index.
OS << "static bool checkDecoderPredicate(unsigned Idx, const FeatureBitset "
"&Bits) {\n";
OS << " switch (Idx) {\n";
OS << " default: llvm_unreachable(\"Invalid index!\");\n";
for (const auto &[Index, Predicate] : enumerate(Predicates)) {
OS << " case " << Index << ":\n";
OS << " return (" << Predicate << ");\n";
}
OS << " }\n";
OS << "}\n\n";
}
void DecoderEmitter::emitDecoderFunction(formatted_raw_ostream &OS,
DecoderSet &Decoders) const {
// The decoder function is just a big switch statement or a table of function
// pointers based on the input decoder index.
// TODO: When InsnType is large, using uint64_t limits all fields to 64 bits
// It would be better for emitBinaryParser to use a 64-bit tmp whenever
// possible but fall back to an InsnType-sized tmp for truly large fields.
StringRef TmpTypeDecl =
"using TmpType = std::conditional_t<std::is_integral<InsnType>::value, "
"InsnType, uint64_t>;\n";
StringRef DecodeParams =
"DecodeStatus S, InsnType insn, MCInst &MI, uint64_t Address, const "
"MCDisassembler *Decoder, bool &DecodeComplete";
if (UseFnTableInDecodeToMCInst) {
// Emit a function for each case first.
for (const auto &[Index, Decoder] : enumerate(Decoders)) {
OS << "template <typename InsnType>\n";
OS << "static DecodeStatus decodeFn" << Index << "(" << DecodeParams
<< ") {\n";
OS << " using namespace llvm::MCD;\n";
OS << " " << TmpTypeDecl;
OS << " [[maybe_unused]] TmpType tmp;\n";
OS << Decoder;
OS << " return S;\n";
OS << "}\n\n";
}
}
OS << "// Handling " << Decoders.size() << " cases.\n";
OS << "template <typename InsnType>\n";
OS << "static DecodeStatus decodeToMCInst(unsigned Idx, " << DecodeParams
<< ") {\n";
OS << " using namespace llvm::MCD;\n";
OS << " DecodeComplete = true;\n";
if (UseFnTableInDecodeToMCInst) {
// Build a table of function pointers
OS << " using DecodeFnTy = DecodeStatus (*)(" << DecodeParams << ");\n";
OS << " static constexpr DecodeFnTy decodeFnTable[] = {\n";
for (size_t Index : llvm::seq(Decoders.size()))
OS << " decodeFn" << Index << ",\n";
OS << " };\n";
OS << " if (Idx >= " << Decoders.size() << ")\n";
OS << " llvm_unreachable(\"Invalid decoder index!\");\n";
OS << " return decodeFnTable[Idx](S, insn, MI, Address, Decoder, "
"DecodeComplete);\n";
} else {
OS << " " << TmpTypeDecl;
OS << " TmpType tmp;\n";
OS << " switch (Idx) {\n";
OS << " default: llvm_unreachable(\"Invalid decoder index!\");\n";
for (const auto &[Index, Decoder] : enumerate(Decoders)) {
OS << " case " << Index << ":\n";
OS << Decoder;
OS << " return S;\n";
}
OS << " }\n";
}
OS << "}\n";
}
/// 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, indent Indent) const {
if (Parent)
Parent->dumpStack(OS, Indent);
OS << Indent;
printKnownBits(OS, FilterBits, '.');
OS << '\n';
}
// Calculates the island(s) needed to decode the instruction.
// This returns a list of undecoded bits of an instructions, for example,
// Inst{20} = 1 && Inst{3-0} == 0b1111 represents two islands of yet-to-be
// decoded bits in order to verify that the instruction matches the Opcode.
std::vector<FilterChooser::Island>
FilterChooser::getIslands(const KnownBits &EncodingBits) const {
std::vector<Island> Islands;
uint64_t FieldVal;
unsigned StartBit;
// 0: Init
// 1: Water (the bit value does not affect decoding)
// 2: Island (well-known bit value needed for decoding)
unsigned State = 0;
for (unsigned i = 0; i < BitWidth; ++i) {
bool IsKnown = EncodingBits.Zero[i] || EncodingBits.One[i];
bool Filtered = isPositionFiltered(i);
switch (State) {
default:
llvm_unreachable("Unreachable code!");
case 0:
case 1:
if (Filtered || !IsKnown) {
State = 1; // Still in Water
} else {
State = 2; // Into the Island
StartBit = i;
FieldVal = static_cast<uint64_t>(EncodingBits.One[i]);
}
break;
case 2:
if (Filtered || !IsKnown) {
State = 1; // Into the Water
Islands.push_back({StartBit, i - StartBit, FieldVal});
} else {
State = 2; // Still in Island
FieldVal |= static_cast<uint64_t>(EncodingBits.One[i])
<< (i - StartBit);
}
break;
}
}
// If we are still in Island after the loop, do some housekeeping.
if (State == 2)
Islands.push_back({StartBit, BitWidth - StartBit, FieldVal});
return Islands;
}
void 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;
if (UseInsertBits) {
OS << Indent << "tmp = 0x";
OS.write_hex(OpInfo.InitValue);
OS << ";\n";
}
for (const EncodingField &EF : OpInfo) {
OS << Indent;
if (UseInsertBits)
OS << "insertBits(tmp, ";
else
OS << "tmp = ";
OS << "fieldFromInstruction(insn, " << EF.Base << ", " << EF.Width << ')';
if (UseInsertBits)
OS << ", " << EF.Offset << ", " << EF.Width << ')';
else if (EF.Offset != 0)
OS << " << " << EF.Offset;
OS << ";\n";
}
if (!Decoder.empty()) {
OS << Indent << "if (!Check(S, " << Decoder
<< "(MI, tmp, Address, Decoder))) { "
<< (OpInfo.HasCompleteDecoder ? "" : "DecodeComplete = false; ")
<< "return MCDisassembler::Fail; }\n";
} else {
OS << Indent << "MI.addOperand(MCOperand::createImm(tmp));\n";
}
}
void FilterChooser::emitDecoder(raw_ostream &OS, indent Indent,
unsigned EncodingID) const {
const InstructionEncoding &Encoding = Encodings[EncodingID];
// If a custom instruction decoder was specified, use that.
StringRef DecoderMethod = Encoding.getDecoderMethod();
if (!DecoderMethod.empty()) {
OS << Indent << "if (!Check(S, " << DecoderMethod
<< "(MI, insn, Address, Decoder))) { "
<< (Encoding.hasCompleteDecoder() ? "" : "DecodeComplete = false; ")
<< "return MCDisassembler::Fail; }\n";
return;
}
for (const OperandInfo &Op : Encoding.getOperands())
if (Op.numFields())
emitBinaryParser(OS, Indent, Op);
}
unsigned FilterChooser::getDecoderIndex(DecoderSet &Decoders,
unsigned EncodingID) 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);
indent Indent(UseFnTableInDecodeToMCInst ? 2 : 4);
emitDecoder(S, Indent, EncodingID);
// Using the full decoder string as the key value here is a bit
// heavyweight, but is effective. If the string comparisons become a
// performance concern, we can implement a mangling of the predicate
// data easily enough with a map back to the actual string. That's
// overkill for now, though.
// Make sure the predicate is in the table.
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 std::distance(Decoders.begin(), P);
}
// If ParenIfBinOp is true, print a surrounding () if Val uses && or ||.
bool FilterChooser::emitPredicateMatchAux(const Init &Val, bool ParenIfBinOp,
raw_ostream &OS) const {
if (const auto *D = dyn_cast<DefInit>(&Val)) {
if (!D->getDef()->isSubClassOf("SubtargetFeature"))
return true;
OS << "Bits[" << Emitter->PredicateNamespace << "::" << D->getAsString()
<< "]";
return false;
}
if (const auto *D = dyn_cast<DagInit>(&Val)) {
std::string Op = D->getOperator()->getAsString();
if (Op == "not" && D->getNumArgs() == 1) {
OS << '!';
return emitPredicateMatchAux(*D->getArg(0), true, OS);
}
if ((Op == "any_of" || Op == "all_of") && D->getNumArgs() > 0) {
bool Paren = D->getNumArgs() > 1 && std::exchange(ParenIfBinOp, true);
if (Paren)
OS << '(';
ListSeparator LS(Op == "any_of" ? " || " : " && ");
for (auto *Arg : D->getArgs()) {
OS << LS;
if (emitPredicateMatchAux(*Arg, ParenIfBinOp, OS))
return true;
}
if (Paren)
OS << ')';
return false;
}
}
return true;
}
bool FilterChooser::emitPredicateMatch(raw_ostream &OS,
unsigned EncodingID) const {
const ListInit *Predicates =
Encodings[EncodingID].getRecord()->getValueAsListInit("Predicates");
bool IsFirstEmission = true;
for (unsigned i = 0; i < Predicates->size(); ++i) {
const Record *Pred = Predicates->getElementAsRecord(i);
if (!Pred->getValue("AssemblerMatcherPredicate"))
continue;
if (!isa<DagInit>(Pred->getValue("AssemblerCondDag")->getValue()))
continue;
if (!IsFirstEmission)
OS << " && ";
if (emitPredicateMatchAux(*Pred->getValueAsDag("AssemblerCondDag"),
Predicates->size() > 1, OS))
PrintFatalError(Pred->getLoc(), "Invalid AssemblerCondDag!");
IsFirstEmission = false;
}
return !Predicates->empty();
}
bool FilterChooser::doesOpcodeNeedPredicate(unsigned EncodingID) const {
const ListInit *Predicates =
Encodings[EncodingID].getRecord()->getValueAsListInit("Predicates");
for (unsigned i = 0; i < Predicates->size(); ++i) {
const Record *Pred = Predicates->getElementAsRecord(i);
if (!Pred->getValue("AssemblerMatcherPredicate"))
continue;
if (isa<DagInit>(Pred->getValue("AssemblerCondDag")->getValue()))
return true;
}
return false;
}
unsigned FilterChooser::getPredicateIndex(DecoderTableInfo &TableInfo,
StringRef Predicate) const {
// Using the full predicate string as the key value here is a bit
// heavyweight, but is effective. If the string comparisons become a
// performance concern, we can implement a mangling of the predicate
// data easily enough with a map back to the actual string. That's
// overkill for now, though.
// Make sure the predicate is in the table.
TableInfo.Predicates.insert(CachedHashString(Predicate));
// Now figure out the index for when we write out the table.
PredicateSet::const_iterator P = find(TableInfo.Predicates, Predicate);
return (unsigned)(P - TableInfo.Predicates.begin());
}
void FilterChooser::emitPredicateTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const {
if (!doesOpcodeNeedPredicate(EncodingID))
return;
// Build up the predicate string.
SmallString<256> Predicate;
// FIXME: emitPredicateMatch() functions can take a buffer directly rather
// than a stream.
raw_svector_ostream PS(Predicate);
emitPredicateMatch(PS, EncodingID);
// Figure out the index into the predicate table for the predicate just
// computed.
unsigned PIdx = getPredicateIndex(TableInfo, PS.str());
const uint8_t DecoderOp = TableInfo.isOutermostScope()
? MCD::OPC_CheckPredicateOrFail
: MCD::OPC_CheckPredicate;
TableInfo.Table.push_back(DecoderOp);
TableInfo.Table.insertULEB128(PIdx);
if (DecoderOp == MCD::OPC_CheckPredicate) {
// Push location for NumToSkip backpatching.
TableInfo.FixupStack.back().push_back(TableInfo.Table.insertNumToSkip());
}
}
void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const {
const InstructionEncoding &Encoding = Encodings[EncodingID];
const KnownBits &InstBits = Encoding.getInstBits();
const APInt &SFBits = Encoding.getSoftFailBits();
if (SFBits.isZero())
return;
APInt PositiveMask(BitWidth, 0ULL);
APInt NegativeMask(BitWidth, 0ULL);
for (unsigned i = 0; i < BitWidth; ++i) {
if (!SFBits[i])
continue;
if (InstBits.Zero[i]) {
// The bit is meant to be false, so emit a check to see if it is true.
PositiveMask.setBit(i);
} else if (InstBits.One[i]) {
// The bit is meant to be true, so emit a check to see if it is false.
NegativeMask.setBit(i);
}
}
bool NeedPositiveMask = PositiveMask.getBoolValue();
bool NeedNegativeMask = NegativeMask.getBoolValue();
if (!NeedPositiveMask && !NeedNegativeMask)
return;
TableInfo.Table.push_back(MCD::OPC_SoftFail);
TableInfo.Table.insertULEB128(PositiveMask.getZExtValue());
TableInfo.Table.insertULEB128(NegativeMask.getZExtValue());
}
// Emits table entries to decode the singleton.
void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
unsigned EncodingID) const {
KnownBits EncodingBits = getMandatoryEncodingBits(EncodingID);
// Look for islands of undecoded bits of the singleton.
std::vector<Island> Islands = getIslands(EncodingBits);
// Emit the predicate table entry if one is needed.
emitPredicateTableEntry(TableInfo, EncodingID);
// Check any additional encoding fields needed.
for (const Island &Ilnd : reverse(Islands)) {
unsigned NumBits = Ilnd.NumBits;
assert(isUInt<8>(NumBits) && "NumBits overflowed uint8 table entry!");
const uint8_t DecoderOp = TableInfo.isOutermostScope()
? MCD::OPC_CheckFieldOrFail
: MCD::OPC_CheckField;
TableInfo.Table.push_back(DecoderOp);
TableInfo.Table.insertULEB128(Ilnd.StartBit);
TableInfo.Table.push_back(NumBits);
TableInfo.Table.insertULEB128(Ilnd.FieldVal);
if (DecoderOp == MCD::OPC_CheckField) {
// Allocate space in the table for fixup so all our relative position
// calculations work OK even before we fully resolve the real value here.
// Push location for NumToSkip backpatching.
TableInfo.FixupStack.back().push_back(TableInfo.Table.insertNumToSkip());
}
}
// Check for soft failure of the match.
emitSoftFailTableEntry(TableInfo, EncodingID);
unsigned DIdx = getDecoderIndex(TableInfo.Decoders, EncodingID);
// Produce OPC_Decode or OPC_TryDecode opcode based on the information
// whether the instruction decoder is complete or not. If it is complete
// then it handles all possible values of remaining variable/unfiltered bits
// and for any value can determine if the bitpattern is a valid instruction
// or not. This means OPC_Decode will be the final step in the decoding
// process. If it is not complete, then the Fail return code from the
// 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
: (TableInfo.isOutermostScope() ? MCD::OPC_TryDecodeOrFail
: MCD::OPC_TryDecode);
TableInfo.Table.push_back(DecoderOp);
const Record *InstDef = Encodings[EncodingID].getInstruction()->TheDef;
TableInfo.Table.insertULEB128(Emitter->getTarget().getInstrIntValue(InstDef));
TableInfo.Table.insertULEB128(DIdx);
if (DecoderOp == MCD::OPC_TryDecode) {
// Push location for NumToSkip backpatching.
TableInfo.FixupStack.back().push_back(TableInfo.Table.insertNumToSkip());
}
}
// Emits table entries to decode the singleton, and then to decode the rest.
void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
const Filter &Best) const {
// complex singletons need predicate checks from the first singleton
// to refer forward to the variable filterchooser that follows.
TableInfo.pushScope();
emitSingletonTableEntry(TableInfo, Best.getSingletonEncodingID());
TableInfo.popScope();
Best.getVariableFC().emitTableEntries(TableInfo);
}
// Assign a single filter and run with it. Top level API client can initialize
// with a single filter to start the filtering process.
void FilterChooser::runSingleFilter(unsigned startBit, unsigned numBit) {
BestFilter = std::make_unique<Filter>(*this, startBit, numBit);
BestFilter->recurse();
}
// reportRegion is a helper function for filterProcessor to mark a region as
// eligible for use as a filter region.
void FilterChooser::reportRegion(std::vector<std::unique_ptr<Filter>> &Filters,
bitAttr_t RA, unsigned StartBit,
unsigned BitIndex, bool AllowMixed) {
if (AllowMixed ? RA == ATTR_MIXED : RA == ATTR_ALL_SET)
Filters.push_back(
std::make_unique<Filter>(*this, StartBit, BitIndex - StartBit));
}
// FilterProcessor scans the well-known encoding bits of the instructions and
// builds up a list of candidate filters. It chooses the best filter and
// recursively descends down the decoding tree.
bool FilterChooser::filterProcessor(ArrayRef<bitAttr_t> BitAttrs,
bool AllowMixed, bool Greedy) {
assert(EncodingIDs.size() >= 2 && "Nothing to filter");
// Heuristics. See also doFilter()'s "Heuristics" comment when num of
// instructions is 3.
if (AllowMixed && !Greedy) {
assert(EncodingIDs.size() == 3);
for (unsigned EncodingID : EncodingIDs) {
KnownBits EncodingBits = getMandatoryEncodingBits(EncodingID);
// Look for islands of undecoded bits of any instruction.
std::vector<Island> Islands = getIslands(EncodingBits);
if (!Islands.empty()) {
// Found an instruction with island(s). Now just assign a filter.
runSingleFilter(Islands[0].StartBit, Islands[0].NumBits);
return true;
}
}
}
// The regionAttr automaton consumes the bitAttrs automatons' state,
// lowest-to-highest.
//
// Input symbols: F(iltered), (all_)S(et), (all_)U(nset), M(ixed)
// States: NONE, ALL_SET, MIXED
// Initial state: NONE
//
// (NONE) ----- F --> (NONE)
// (NONE) ----- S --> (ALL_SET) ; and set region start
// (NONE) ----- U --> (NONE)
// (NONE) ----- M --> (MIXED) ; and set region start
// (ALL_SET) -- F --> (NONE) ; and report an ALL_SET region
// (ALL_SET) -- S --> (ALL_SET)
// (ALL_SET) -- U --> (NONE) ; and report an ALL_SET region
// (ALL_SET) -- M --> (MIXED) ; and report an ALL_SET region
// (MIXED) ---- F --> (NONE) ; and report a MIXED region
// (MIXED) ---- S --> (ALL_SET) ; and report a MIXED region
// (MIXED) ---- U --> (NONE) ; and report a MIXED region
// (MIXED) ---- M --> (MIXED)
bitAttr_t RA = ATTR_NONE;
unsigned StartBit = 0;
std::vector<std::unique_ptr<Filter>> Filters;
for (unsigned BitIndex = 0; BitIndex < BitWidth; ++BitIndex) {
bitAttr_t bitAttr = BitAttrs[BitIndex];
assert(bitAttr != ATTR_NONE && "Bit without attributes");
switch (RA) {
case ATTR_NONE:
switch (bitAttr) {
case ATTR_FILTERED:
break;
case ATTR_ALL_SET:
StartBit = BitIndex;
RA = ATTR_ALL_SET;
break;
case ATTR_ALL_UNSET:
break;
case ATTR_MIXED:
StartBit = BitIndex;
RA = ATTR_MIXED;
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_ALL_SET:
switch (bitAttr) {
case ATTR_FILTERED:
reportRegion(Filters, RA, StartBit, BitIndex, AllowMixed);
RA = ATTR_NONE;
break;
case ATTR_ALL_SET:
break;
case ATTR_ALL_UNSET:
reportRegion(Filters, RA, StartBit, BitIndex, AllowMixed);
RA = ATTR_NONE;
break;
case ATTR_MIXED:
reportRegion(Filters, RA, StartBit, BitIndex, AllowMixed);
StartBit = BitIndex;
RA = ATTR_MIXED;
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_MIXED:
switch (bitAttr) {
case ATTR_FILTERED:
reportRegion(Filters, RA, StartBit, BitIndex, AllowMixed);
StartBit = BitIndex;
RA = ATTR_NONE;
break;
case ATTR_ALL_SET:
reportRegion(Filters, RA, StartBit, BitIndex, AllowMixed);
StartBit = BitIndex;
RA = ATTR_ALL_SET;
break;
case ATTR_ALL_UNSET:
reportRegion(Filters, RA, StartBit, BitIndex, AllowMixed);
RA = ATTR_NONE;
break;
case ATTR_MIXED:
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_ALL_UNSET:
llvm_unreachable("regionAttr state machine has no ATTR_UNSET state");
case ATTR_FILTERED:
llvm_unreachable("regionAttr state machine has no ATTR_FILTERED state");
}
}
// At the end, if we're still in ALL_SET or MIXED states, report a region
switch (RA) {
case ATTR_NONE:
break;
case ATTR_FILTERED:
break;
case ATTR_ALL_SET:
reportRegion(Filters, RA, StartBit, BitWidth, AllowMixed);
break;
case ATTR_ALL_UNSET:
break;
case ATTR_MIXED:
reportRegion(Filters, RA, StartBit, BitWidth, AllowMixed);
break;
}
// We have finished with the filter processings. Now it's time to choose
// the best performing filter.
unsigned BestIndex = 0;
bool AllUseless = true;
unsigned BestScore = 0;
for (const auto &[Idx, Filter] : enumerate(Filters)) {
unsigned Usefulness = Filter->usefulness();
if (Usefulness)
AllUseless = false;
if (Usefulness > BestScore) {
BestIndex = Idx;
BestScore = Usefulness;
}
}
if (AllUseless)
return false;
BestFilter = std::move(Filters[BestIndex]);
BestFilter->recurse();
return true;
} // end of FilterChooser::filterProcessor(bool)
// Decides on the best configuration of filter(s) to use in order to decode
// the instructions. A conflict of instructions may occur, in which case we
// dump the conflict set to the standard error.
void FilterChooser::doFilter() {
assert(!EncodingIDs.empty() && "FilterChooser created with no instructions");
// No filter needed.
if (EncodingIDs.size() < 2)
return;
// We maintain BIT_WIDTH copies of the bitAttrs automaton.
// The automaton consumes the corresponding bit from each
// instruction.
//
// Input symbols: 0, 1, _ (unset), and . (any of the above).
// States: NONE, FILTERED, ALL_SET, ALL_UNSET, and MIXED.
// Initial state: NONE.
//
// (NONE) ------- [01] -> (ALL_SET)
// (NONE) ------- _ ----> (ALL_UNSET)
// (ALL_SET) ---- [01] -> (ALL_SET)
// (ALL_SET) ---- _ ----> (MIXED)
// (ALL_UNSET) -- [01] -> (MIXED)
// (ALL_UNSET) -- _ ----> (ALL_UNSET)
// (MIXED) ------ . ----> (MIXED)
// (FILTERED)---- . ----> (FILTERED)
SmallVector<bitAttr_t, 128> BitAttrs(BitWidth, ATTR_NONE);
// FILTERED bit positions provide no entropy and are not worthy of pursuing.
// Filter::recurse() set either 1 or 0 for each position.
for (unsigned BitIndex = 0; BitIndex < BitWidth; ++BitIndex)
if (isPositionFiltered(BitIndex))
BitAttrs[BitIndex] = ATTR_FILTERED;
for (unsigned EncodingID : EncodingIDs) {
KnownBits EncodingBits = getMandatoryEncodingBits(EncodingID);
for (unsigned BitIndex = 0; BitIndex < BitWidth; ++BitIndex) {
bool IsKnown = EncodingBits.Zero[BitIndex] || EncodingBits.One[BitIndex];
switch (BitAttrs[BitIndex]) {
case ATTR_NONE:
if (IsKnown)
BitAttrs[BitIndex] = ATTR_ALL_SET;
else
BitAttrs[BitIndex] = ATTR_ALL_UNSET;
break;
case ATTR_ALL_SET:
if (!IsKnown)
BitAttrs[BitIndex] = ATTR_MIXED;
break;
case ATTR_ALL_UNSET:
if (IsKnown)
BitAttrs[BitIndex] = ATTR_MIXED;
break;
case ATTR_MIXED:
case ATTR_FILTERED:
break;
}
}
}
// Try regions of consecutive known bit values first.
if (filterProcessor(BitAttrs, /*AllowMixed=*/false))
return;
// Then regions of mixed bits (both known and unitialized bit values allowed).
if (filterProcessor(BitAttrs, /*AllowMixed=*/true))
return;
// Heuristics to cope with conflict set {t2CMPrs, t2SUBSrr, t2SUBSrs} where
// no single instruction for the maximum ATTR_MIXED region Inst{14-4} has a
// well-known encoding pattern. In such case, we backtrack and scan for the
// the very first consecutive ATTR_ALL_SET region and assign a filter to it.
if (EncodingIDs.size() == 3 &&
filterProcessor(BitAttrs, /*AllowMixed=*/true, /*Greedy=*/false))
return;
// We don't know how to decode these instructions! Dump the
// conflict set and bail.
assert(!BestFilter);
// Print out useful conflict information for postmortem analysis.
errs() << "Decoding Conflict:\n";
// Dump filters.
indent Indent(4);
dumpStack(errs(), Indent);
// Dump encodings.
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Enc = Encodings[EncodingID];
errs() << Indent;
printKnownBits(errs(), getMandatoryEncodingBits(EncodingID), '_');
errs() << " " << Enc.getName() << '\n';
}
PrintFatalError("Decoding conflict encountered");
}
// emitTableEntries - Emit state machine entries to decode our share of
// instructions.
void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
if (EncodingIDs.size() == 1) {
// There is only one instruction in the set, which is great!
// Call emitSingletonDecoder() to see whether there are any remaining
// encodings bits.
emitSingletonTableEntry(TableInfo, EncodingIDs[0]);
return;
}
// Use the best filter to do the decoding!
if (BestFilter->hasSingleFilteredID())
emitSingletonTableEntry(TableInfo, *BestFilter);
else
BestFilter->emitTableEntry(TableInfo);
}
static std::string findOperandDecoderMethod(const Record *Record) {
std::string Decoder;
const RecordVal *DecoderString = Record->getValue("DecoderMethod");
const StringInit *String =
DecoderString ? dyn_cast<StringInit>(DecoderString->getValue()) : nullptr;
if (String) {
Decoder = String->getValue().str();
if (!Decoder.empty())
return Decoder;
}
if (Record->isSubClassOf("RegisterOperand"))
// Allows use of a DecoderMethod in referenced RegisterClass if set.
return findOperandDecoderMethod(Record->getValueAsDef("RegClass"));
if (Record->isSubClassOf("RegisterClass")) {
Decoder = "Decode" + Record->getName().str() + "RegisterClass";
} else if (Record->isSubClassOf("PointerLikeRegClass")) {
Decoder = "DecodePointerLikeRegClass" +
utostr(Record->getValueAsInt("RegClassKind"));
}
return Decoder;
}
OperandInfo getOpInfo(const Record *TypeRecord) {
const RecordVal *HasCompleteDecoderVal =
TypeRecord->getValue("hasCompleteDecoder");
const BitInit *HasCompleteDecoderBit =
HasCompleteDecoderVal
? dyn_cast<BitInit>(HasCompleteDecoderVal->getValue())
: nullptr;
bool HasCompleteDecoder =
HasCompleteDecoderBit ? HasCompleteDecoderBit->getValue() : true;
return OperandInfo(findOperandDecoderMethod(TypeRecord), HasCompleteDecoder);
}
void InstructionEncoding::parseVarLenEncoding(const VarLenInst &VLI) {
InstBits = KnownBits(VLI.size());
SoftFailBits = APInt(VLI.size(), 0);
// Parse Inst field.
unsigned I = 0;
for (const EncodingSegment &S : VLI) {
if (const auto *SegmentBits = dyn_cast<BitsInit>(S.Value)) {
for (const Init *V : SegmentBits->getBits()) {
if (const auto *B = dyn_cast<BitInit>(V)) {
if (B->getValue())
InstBits.One.setBit(I);
else
InstBits.Zero.setBit(I);
}
++I;
}
} else if (const auto *B = dyn_cast<BitInit>(S.Value)) {
if (B->getValue())
InstBits.One.setBit(I);
else
InstBits.Zero.setBit(I);
++I;
} else {
I += S.BitWidth;
}
}
assert(I == VLI.size());
}
void InstructionEncoding::parseFixedLenEncoding(const BitsInit &Bits) {
InstBits = KnownBits(Bits.getNumBits());
SoftFailBits = APInt(Bits.getNumBits(), 0);
// Parse Inst field.
for (auto [I, V] : enumerate(Bits.getBits())) {
if (const auto *B = dyn_cast<BitInit>(V)) {
if (B->getValue())
InstBits.One.setBit(I);
else
InstBits.Zero.setBit(I);
}
}
// Parse SoftFail field.
if (const RecordVal *SoftFailField = EncodingDef->getValue("SoftFail")) {
const auto *SFBits = dyn_cast<BitsInit>(SoftFailField->getValue());
if (!SFBits || SFBits->getNumBits() != Bits.getNumBits()) {
PrintNote(EncodingDef->getLoc(), "in record");
PrintFatalError(SoftFailField,
formatv("SoftFail field, if defined, must be "
"of the same type as Inst, which is bits<{}>",
Bits.getNumBits()));
}
for (auto [I, V] : enumerate(SFBits->getBits())) {
if (const auto *B = dyn_cast<BitInit>(V); B && B->getValue()) {
if (!InstBits.Zero[I] && !InstBits.One[I]) {
PrintNote(EncodingDef->getLoc(), "in record");
PrintError(SoftFailField,
formatv("SoftFail{{{0}} = 1 requires Inst{{{0}} "
"to be fully defined (0 or 1, not '?')",
I));
}
SoftFailBits.setBit(I);
}
}
}
}
void InstructionEncoding::parseVarLenOperands(const VarLenInst &VLI) {
SmallVector<int> TiedTo;
for (const auto &[Idx, Op] : enumerate(Inst->Operands)) {
if (Op.MIOperandInfo && Op.MIOperandInfo->getNumArgs() > 0)
for (auto *Arg : Op.MIOperandInfo->getArgs())
Operands.push_back(getOpInfo(cast<DefInit>(Arg)->getDef()));
else
Operands.push_back(getOpInfo(Op.Rec));
int TiedReg = Op.getTiedRegister();
TiedTo.push_back(-1);
if (TiedReg != -1) {
TiedTo[Idx] = TiedReg;
TiedTo[TiedReg] = Idx;
}
}
unsigned CurrBitPos = 0;
for (const auto &EncodingSegment : VLI) {
unsigned Offset = 0;
StringRef OpName;
if (const StringInit *SI = dyn_cast<StringInit>(EncodingSegment.Value)) {
OpName = SI->getValue();
} else if (const DagInit *DI = dyn_cast<DagInit>(EncodingSegment.Value)) {
OpName = cast<StringInit>(DI->getArg(0))->getValue();
Offset = cast<IntInit>(DI->getArg(2))->getValue();
}
if (!OpName.empty()) {
auto OpSubOpPair = Inst->Operands.parseOperandName(OpName);
unsigned OpIdx = Inst->Operands.getFlattenedOperandNumber(OpSubOpPair);
Operands[OpIdx].addField(CurrBitPos, EncodingSegment.BitWidth, Offset);
if (!EncodingSegment.CustomDecoder.empty())
Operands[OpIdx].Decoder = EncodingSegment.CustomDecoder.str();
int TiedReg = TiedTo[OpSubOpPair.first];
if (TiedReg != -1) {
unsigned OpIdx = Inst->Operands.getFlattenedOperandNumber(
{TiedReg, OpSubOpPair.second});
Operands[OpIdx].addField(CurrBitPos, EncodingSegment.BitWidth, Offset);
}
}
CurrBitPos += EncodingSegment.BitWidth;
}
}
static void debugDumpRecord(const Record &Rec) {
// Dump the record, so we can see what's going on.
PrintNote([&Rec](raw_ostream &OS) {
OS << "Dumping record for previous error:\n";
OS << Rec;
});
}
/// For an operand field named OpName: populate OpInfo.InitValue with the
/// constant-valued bit values, and OpInfo.Fields with the ranges of bits to
/// insert from the decoded instruction.
static void addOneOperandFields(const Record *EncodingDef, const BitsInit &Bits,
std::map<StringRef, StringRef> &TiedNames,
StringRef OpName, OperandInfo &OpInfo) {
// Some bits of the operand may be required to be 1 depending on the
// instruction's encoding. Collect those bits.
if (const RecordVal *EncodedValue = EncodingDef->getValue(OpName))
if (const BitsInit *OpBits = dyn_cast<BitsInit>(EncodedValue->getValue()))
for (unsigned I = 0; I < OpBits->getNumBits(); ++I)
if (const BitInit *OpBit = dyn_cast<BitInit>(OpBits->getBit(I)))
if (OpBit->getValue())
OpInfo.InitValue |= 1ULL << I;
for (unsigned I = 0, J = 0; I != Bits.getNumBits(); I = J) {
const VarInit *Var;
unsigned Offset = 0;
for (; J != Bits.getNumBits(); ++J) {
const VarBitInit *BJ = dyn_cast<VarBitInit>(Bits.getBit(J));
if (BJ) {
Var = dyn_cast<VarInit>(BJ->getBitVar());
if (I == J)
Offset = BJ->getBitNum();
else if (BJ->getBitNum() != Offset + J - I)
break;
} else {
Var = dyn_cast<VarInit>(Bits.getBit(J));
}
if (!Var ||
(Var->getName() != OpName && Var->getName() != TiedNames[OpName]))
break;
}
if (I == J)
++J;
else
OpInfo.addField(I, J - I, Offset);
}
}
void InstructionEncoding::parseFixedLenOperands(const BitsInit &Bits) {
const Record &Def = *Inst->TheDef;
// Gather the outputs/inputs of the instruction, so we can find their
// positions in the encoding. This assumes for now that they appear in the
// MCInst in the order that they're listed.
std::vector<std::pair<const Init *, StringRef>> InOutOperands;
const DagInit *Out = Def.getValueAsDag("OutOperandList");
const DagInit *In = Def.getValueAsDag("InOperandList");
for (const auto &[Idx, Arg] : enumerate(Out->getArgs()))
InOutOperands.emplace_back(Arg, Out->getArgNameStr(Idx));
for (const auto &[Idx, Arg] : enumerate(In->getArgs()))
InOutOperands.emplace_back(Arg, In->getArgNameStr(Idx));
// Search for tied operands, so that we can correctly instantiate
// operands that are not explicitly represented in the encoding.
std::map<StringRef, StringRef> TiedNames;
for (const auto &Op : Inst->Operands) {
for (const auto &[J, CI] : enumerate(Op.Constraints)) {
if (!CI.isTied())
continue;
std::pair<unsigned, unsigned> SO =
Inst->Operands.getSubOperandNumber(CI.getTiedOperand());
StringRef TiedName = Inst->Operands[SO.first].SubOpNames[SO.second];
if (TiedName.empty())
TiedName = Inst->Operands[SO.first].Name;
StringRef MyName = Op.SubOpNames[J];
if (MyName.empty())
MyName = Op.Name;
TiedNames[MyName] = TiedName;
TiedNames[TiedName] = MyName;
}
}
// For each operand, see if we can figure out where it is encoded.
for (const auto &Op : InOutOperands) {
const Init *OpInit = Op.first;
StringRef OpName = Op.second;
// We're ready to find the instruction encoding locations for this
// operand.
// First, find the operand type ("OpInit"), and sub-op names
// ("SubArgDag") if present.
const DagInit *SubArgDag = dyn_cast<DagInit>(OpInit);
if (SubArgDag)
OpInit = SubArgDag->getOperator();
const Record *OpTypeRec = cast<DefInit>(OpInit)->getDef();
// Lookup the sub-operands from the operand type record (note that only
// Operand subclasses have MIOperandInfo, see CodeGenInstruction.cpp).
const DagInit *SubOps = OpTypeRec->isSubClassOf("Operand")
? OpTypeRec->getValueAsDag("MIOperandInfo")
: nullptr;
// Lookup the decoder method and construct a new OperandInfo to hold our
// result.
OperandInfo OpInfo = getOpInfo(OpTypeRec);
// If we have named sub-operands...
if (SubArgDag) {
// Then there should not be a custom decoder specified on the top-level
// type.
if (!OpInfo.Decoder.empty()) {
PrintError(EncodingDef,
"DecoderEmitter: operand \"" + OpName + "\" has type \"" +
OpInit->getAsString() +
"\" with a custom DecoderMethod, but also named "
"sub-operands.");
continue;
}
// Decode each of the sub-ops separately.
assert(SubOps && SubArgDag->getNumArgs() == SubOps->getNumArgs());
for (const auto &[I, Arg] : enumerate(SubOps->getArgs())) {
StringRef SubOpName = SubArgDag->getArgNameStr(I);
OperandInfo SubOpInfo = getOpInfo(cast<DefInit>(Arg)->getDef());
addOneOperandFields(EncodingDef, Bits, TiedNames, SubOpName, SubOpInfo);
Operands.push_back(std::move(SubOpInfo));
}
continue;
}
// Otherwise, if we have an operand with sub-operands, but they aren't
// named...
if (SubOps && OpInfo.Decoder.empty()) {
// If it's a single sub-operand, and no custom decoder, use the decoder
// from the one sub-operand.
if (SubOps->getNumArgs() == 1)
OpInfo = getOpInfo(cast<DefInit>(SubOps->getArg(0))->getDef());
// If we have multiple sub-ops, there'd better have a custom
// decoder. (Otherwise we don't know how to populate them properly...)
if (SubOps->getNumArgs() > 1) {
PrintError(EncodingDef,
"DecoderEmitter: operand \"" + OpName +
"\" uses MIOperandInfo with multiple ops, but doesn't "
"have a custom decoder!");
debugDumpRecord(*EncodingDef);
continue;
}
}
addOneOperandFields(EncodingDef, Bits, TiedNames, OpName, OpInfo);
// FIXME: it should be an error not to find a definition for a given
// operand, rather than just failing to add it to the resulting
// instruction! (This is a longstanding bug, which will be addressed in an
// upcoming change.)
if (OpInfo.numFields() > 0)
Operands.push_back(std::move(OpInfo));
}
}
InstructionEncoding::InstructionEncoding(const Record *EncodingDef,
const CodeGenInstruction *Inst)
: EncodingDef(EncodingDef), Inst(Inst) {
const Record *InstDef = Inst->TheDef;
// Give this encoding a name.
if (EncodingDef != InstDef)
Name = (EncodingDef->getName() + Twine(':')).str();
Name.append(InstDef->getName());
DecoderMethod = EncodingDef->getValueAsString("DecoderMethod");
if (!DecoderMethod.empty())
HasCompleteDecoder = EncodingDef->getValueAsBit("hasCompleteDecoder");
const RecordVal *InstField = EncodingDef->getValue("Inst");
if (const auto *DI = dyn_cast<DagInit>(InstField->getValue())) {
VarLenInst VLI(DI, InstField);
parseVarLenEncoding(VLI);
// If the encoding has a custom decoder, don't bother parsing the operands.
if (DecoderMethod.empty())
parseVarLenOperands(VLI);
} else {
const auto *BI = cast<BitsInit>(InstField->getValue());
parseFixedLenEncoding(*BI);
// If the encoding has a custom decoder, don't bother parsing the operands.
if (DecoderMethod.empty())
parseFixedLenOperands(*BI);
}
if (DecoderMethod.empty()) {
// A generated decoder is always successful if none of the operand
// decoders can fail (all are always successful).
HasCompleteDecoder = all_of(Operands, [](const OperandInfo &Op) {
// By default, a generated operand decoder is assumed to always succeed.
// This can be overridden by the user.
return Op.Decoder.empty() || Op.HasCompleteDecoder;
});
}
}
// emitDecodeInstruction - Emit the templated helper function
// decodeInstruction().
static void emitDecodeInstruction(formatted_raw_ostream &OS, bool IsVarLenInst,
unsigned OpcodeMask) {
const bool HasTryDecode = OpcodeMask & ((1 << MCD::OPC_TryDecode) |
(1 << MCD::OPC_TryDecodeOrFail));
const bool HasCheckPredicate =
OpcodeMask &
((1 << MCD::OPC_CheckPredicate) | (1 << MCD::OPC_CheckPredicateOrFail));
const bool HasSoftFail = OpcodeMask & (1 << MCD::OPC_SoftFail);
OS << R"(
static unsigned decodeNumToSkip(const uint8_t *&Ptr) {
unsigned NumToSkip = *Ptr++;
NumToSkip |= (*Ptr++) << 8;
)";
if (getNumToSkipInBytes() == 3)
OS << " NumToSkip |= (*Ptr++) << 16;\n";
OS << R"( return NumToSkip;
}
template <typename InsnType>
static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,
InsnType insn, uint64_t Address,
const MCDisassembler *DisAsm,
const MCSubtargetInfo &STI)";
if (IsVarLenInst) {
OS << ",\n "
"llvm::function_ref<void(APInt &, uint64_t)> makeUp";
}
OS << ") {\n";
if (HasCheckPredicate)
OS << " const FeatureBitset &Bits = STI.getFeatureBits();\n";
OS << " using namespace llvm::MCD;\n";
OS << R"(
const uint8_t *Ptr = DecodeTable;
uint64_t CurFieldValue = 0;
DecodeStatus S = MCDisassembler::Success;
while (true) {
ptrdiff_t Loc = Ptr - DecodeTable;
const uint8_t DecoderOp = *Ptr++;
switch (DecoderOp) {
default:
errs() << Loc << ": Unexpected decode table opcode: "
<< (int)DecoderOp << '\n';
return MCDisassembler::Fail;
case MCD::OPC_ExtractField: {
// Decode the start value.
unsigned Start = decodeULEB128AndIncUnsafe(Ptr);
unsigned Len = *Ptr++;)";
if (IsVarLenInst)
OS << "\n makeUp(insn, Start + Len);";
OS << R"(
CurFieldValue = fieldFromInstruction(insn, Start, Len);
LLVM_DEBUG(dbgs() << Loc << ": OPC_ExtractField(" << Start << ", "
<< Len << "): " << CurFieldValue << "\n");
break;
}
case MCD::OPC_FilterValue:
case MCD::OPC_FilterValueOrFail: {
bool IsFail = DecoderOp == MCD::OPC_FilterValueOrFail;
// Decode the field value.
uint64_t Val = decodeULEB128AndIncUnsafe(Ptr);
bool Failed = Val != CurFieldValue;
unsigned NumToSkip = IsFail ? 0 : decodeNumToSkip(Ptr);
// Note: Print NumToSkip even for OPC_FilterValueOrFail to simplify debug
// prints.
LLVM_DEBUG({
StringRef OpName = IsFail ? "OPC_FilterValueOrFail" : "OPC_FilterValue";
dbgs() << Loc << ": " << OpName << '(' << Val << ", " << NumToSkip
<< ") " << (Failed ? "FAIL:" : "PASS:")
<< " continuing at " << (Ptr - DecodeTable) << '\n';
});
// Perform the filter operation.
if (Failed) {
if (IsFail)
return MCDisassembler::Fail;
Ptr += NumToSkip;
}
break;
}
case MCD::OPC_CheckField:
case MCD::OPC_CheckFieldOrFail: {
bool IsFail = DecoderOp == MCD::OPC_CheckFieldOrFail;
// Decode the start value.
unsigned Start = decodeULEB128AndIncUnsafe(Ptr);
unsigned Len = *Ptr;)";
if (IsVarLenInst)
OS << "\n makeUp(insn, Start + Len);";
OS << R"(
uint64_t FieldValue = fieldFromInstruction(insn, Start, Len);
// Decode the field value.
unsigned PtrLen = 0;
uint64_t ExpectedValue = decodeULEB128(++Ptr, &PtrLen);
Ptr += PtrLen;
bool Failed = ExpectedValue != FieldValue;
unsigned NumToSkip = IsFail ? 0 : decodeNumToSkip(Ptr);
LLVM_DEBUG({
StringRef OpName = IsFail ? "OPC_CheckFieldOrFail" : "OPC_CheckField";
dbgs() << Loc << ": " << OpName << '(' << Start << ", " << Len << ", "
<< ExpectedValue << ", " << NumToSkip << "): FieldValue = "
<< FieldValue << ", ExpectedValue = " << ExpectedValue << ": "
<< (Failed ? "FAIL\n" : "PASS\n");
});
// If the actual and expected values don't match, skip or fail.
if (Failed) {
if (IsFail)
return MCDisassembler::Fail;
Ptr += NumToSkip;
}
break;
})";
if (HasCheckPredicate) {
OS << R"(
case MCD::OPC_CheckPredicate:
case MCD::OPC_CheckPredicateOrFail: {
bool IsFail = DecoderOp == MCD::OPC_CheckPredicateOrFail;
// Decode the Predicate Index value.
unsigned PIdx = decodeULEB128AndIncUnsafe(Ptr);
unsigned NumToSkip = IsFail ? 0 : decodeNumToSkip(Ptr);
// Check the predicate.
bool Failed = !checkDecoderPredicate(PIdx, Bits);
LLVM_DEBUG({
StringRef OpName = IsFail ? "OPC_CheckPredicateOrFail" : "OPC_CheckPredicate";
dbgs() << Loc << ": " << OpName << '(' << PIdx << ", " << NumToSkip
<< "): " << (Failed ? "FAIL\n" : "PASS\n");
});
if (Failed) {
if (IsFail)
return MCDisassembler::Fail;
Ptr += NumToSkip;
}
break;
})";
}
OS << R"(
case MCD::OPC_Decode: {
// Decode the Opcode value.
unsigned Opc = decodeULEB128AndIncUnsafe(Ptr);
unsigned DecodeIdx = decodeULEB128AndIncUnsafe(Ptr);
MI.clear();
MI.setOpcode(Opc);
bool DecodeComplete;)";
if (IsVarLenInst) {
OS << "\n unsigned Len = InstrLenTable[Opc];\n"
<< " makeUp(insn, Len);";
}
OS << R"(
S = decodeToMCInst(DecodeIdx, S, insn, MI, Address, DisAsm, DecodeComplete);
assert(DecodeComplete);
LLVM_DEBUG(dbgs() << Loc << ": OPC_Decode: opcode " << Opc
<< ", using decoder " << DecodeIdx << ": "
<< (S != MCDisassembler::Fail ? "PASS\n" : "FAIL\n"));
return S;
})";
if (HasTryDecode) {
OS << R"(
case MCD::OPC_TryDecode:
case MCD::OPC_TryDecodeOrFail: {
bool IsFail = DecoderOp == MCD::OPC_TryDecodeOrFail;
// Decode the Opcode value.
unsigned Opc = decodeULEB128AndIncUnsafe(Ptr);
unsigned DecodeIdx = decodeULEB128AndIncUnsafe(Ptr);
unsigned NumToSkip = IsFail ? 0 : decodeNumToSkip(Ptr);
// Perform the decode operation.
MCInst TmpMI;
TmpMI.setOpcode(Opc);
bool DecodeComplete;
S = decodeToMCInst(DecodeIdx, S, insn, TmpMI, Address, DisAsm, DecodeComplete);
LLVM_DEBUG(dbgs() << Loc << ": OPC_TryDecode: opcode " << Opc
<< ", using decoder " << DecodeIdx << ": ");
if (DecodeComplete) {
// Decoding complete.
LLVM_DEBUG(dbgs() << (S != MCDisassembler::Fail ? "PASS\n" : "FAIL\n"));
MI = TmpMI;
return S;
}
assert(S == MCDisassembler::Fail);
if (IsFail) {
LLVM_DEBUG(dbgs() << "FAIL: returning FAIL\n");
return MCDisassembler::Fail;
}
// If the decoding was incomplete, skip.
Ptr += NumToSkip;
LLVM_DEBUG(dbgs() << "FAIL: continuing at " << (Ptr - DecodeTable) << "\n");
// Reset decode status. This also drops a SoftFail status that could be
// set before the decode attempt.
S = MCDisassembler::Success;
break;
})";
}
if (HasSoftFail) {
OS << R"(
case MCD::OPC_SoftFail: {
// Decode the mask values.
uint64_t PositiveMask = decodeULEB128AndIncUnsafe(Ptr);
uint64_t NegativeMask = decodeULEB128AndIncUnsafe(Ptr);
bool Failed = (insn & PositiveMask) != 0 || (~insn & NegativeMask) != 0;
if (Failed)
S = MCDisassembler::SoftFail;
LLVM_DEBUG(dbgs() << Loc << ": OPC_SoftFail: " << (Failed ? "FAIL\n" : "PASS\n"));
break;
})";
}
OS << R"(
case MCD::OPC_Fail: {
LLVM_DEBUG(dbgs() << Loc << ": OPC_Fail\n");
return MCDisassembler::Fail;
}
}
}
llvm_unreachable("bogosity detected in disassembler state machine!");
}
)";
}
/// Collects all HwModes referenced by the target for encoding purposes.
void DecoderEmitter::collectHwModesReferencedForEncodings(
std::vector<unsigned> &HwModeIDs,
NamespacesHwModesMap &NamespacesWithHwModes) const {
SmallBitVector BV(CGH.getNumModeIds());
for (const auto &MS : CGH.getHwModeSelects()) {
for (auto [HwModeID, EncodingDef] : MS.second.Items) {
if (EncodingDef->isSubClassOf("InstructionEncoding")) {
std::string DecoderNamespace =
EncodingDef->getValueAsString("DecoderNamespace").str();
NamespacesWithHwModes[DecoderNamespace].insert(HwModeID);
BV.set(HwModeID);
}
}
}
// FIXME: Can't do `HwModeIDs.assign(BV.set_bits_begin(), BV.set_bits_end())`
// because const_set_bits_iterator_impl is not copy-assignable.
// This breaks some MacOS builds.
llvm::copy(BV.set_bits(), std::back_inserter(HwModeIDs));
}
void DecoderEmitter::handleHwModesUnrelatedEncodings(
unsigned EncodingID, ArrayRef<unsigned> HwModeIDs,
NamespacesHwModesMap &NamespacesWithHwModes) {
switch (DecoderEmitterSuppressDuplicates) {
case SUPPRESSION_DISABLE: {
for (unsigned HwModeID : HwModeIDs)
EncodingIDsByHwMode[HwModeID].push_back(EncodingID);
break;
}
case SUPPRESSION_LEVEL1: {
const Record *InstDef = Encodings[EncodingID].getInstruction()->TheDef;
std::string DecoderNamespace =
InstDef->getValueAsString("DecoderNamespace").str();
auto It = NamespacesWithHwModes.find(DecoderNamespace);
if (It != NamespacesWithHwModes.end()) {
for (unsigned HwModeID : It->second)
EncodingIDsByHwMode[HwModeID].push_back(EncodingID);
} else {
// Only emit the encoding once, as it's DecoderNamespace doesn't
// contain any HwModes.
EncodingIDsByHwMode[DefaultMode].push_back(EncodingID);
}
break;
}
case SUPPRESSION_LEVEL2:
EncodingIDsByHwMode[DefaultMode].push_back(EncodingID);
break;
}
}
/// Checks if the given target-specific non-pseudo instruction
/// is a candidate for decoding.
static bool isDecodableInstruction(const Record *InstDef) {
return !InstDef->getValueAsBit("isAsmParserOnly") &&
!InstDef->getValueAsBit("isCodeGenOnly");
}
/// Checks if the given encoding is valid.
static bool isValidEncoding(const Record *EncodingDef) {
const RecordVal *InstField = EncodingDef->getValue("Inst");
if (!InstField)
return false;
if (const auto *InstInit = dyn_cast<BitsInit>(InstField->getValue())) {
// Fixed-length encoding. Size must be non-zero.
if (!EncodingDef->getValueAsInt("Size"))
return false;
// At least one of the encoding bits must be complete (not '?').
// FIXME: This should take SoftFail field into account.
return !InstInit->allInComplete();
}
if (const auto *InstInit = dyn_cast<DagInit>(InstField->getValue())) {
// Variable-length encoding.
// At least one of the encoding bits must be complete (not '?').
VarLenInst VLI(InstInit, InstField);
return !all_of(VLI, [](const EncodingSegment &Segment) {
return isa<UnsetInit>(Segment.Value);
});
}
// Inst field is neither BitsInit nor DagInit. This is something unsupported.
return false;
}
/// Parses all InstructionEncoding instances and fills internal data structures.
void DecoderEmitter::parseInstructionEncodings() {
// First, collect all encoding-related HwModes referenced by the target.
// And establish a mapping table between DecoderNamespace and HwMode.
// If HwModeNames is empty, add the default mode so we always have one HwMode.
std::vector<unsigned> HwModeIDs;
NamespacesHwModesMap NamespacesWithHwModes;
collectHwModesReferencedForEncodings(HwModeIDs, NamespacesWithHwModes);
if (HwModeIDs.empty())
HwModeIDs.push_back(DefaultMode);
ArrayRef<const CodeGenInstruction *> Instructions =
Target.getTargetNonPseudoInstructions();
Encodings.reserve(Instructions.size());
for (const CodeGenInstruction *Inst : Instructions) {
const Record *InstDef = Inst->TheDef;
if (!isDecodableInstruction(InstDef)) {
++NumEncodingsLackingDisasm;
continue;
}
if (const Record *RV = InstDef->getValueAsOptionalDef("EncodingInfos")) {
EncodingInfoByHwMode EBM(RV, CGH);
for (auto [HwModeID, EncodingDef] : EBM) {
if (!isValidEncoding(EncodingDef)) {
// TODO: Should probably give a warning.
++NumEncodingsOmitted;
continue;
}
unsigned EncodingID = Encodings.size();
Encodings.emplace_back(EncodingDef, Inst);
EncodingIDsByHwMode[HwModeID].push_back(EncodingID);
}
continue; // Ignore encoding specified by Instruction itself.
}
if (!isValidEncoding(InstDef)) {
++NumEncodingsOmitted;
continue;
}
unsigned EncodingID = Encodings.size();
Encodings.emplace_back(InstDef, Inst);
// This instruction is encoded the same on all HwModes.
// According to user needs, add it to all, some, or only the default HwMode.
handleHwModesUnrelatedEncodings(EncodingID, HwModeIDs,
NamespacesWithHwModes);
}
for (const Record *EncodingDef :
RK.getAllDerivedDefinitions("AdditionalEncoding")) {
const Record *InstDef = EncodingDef->getValueAsDef("AliasOf");
// TODO: Should probably give a warning in these cases.
// What's the point of specifying an additional encoding
// if it is invalid or if the instruction is not decodable?
if (!isDecodableInstruction(InstDef)) {
++NumEncodingsLackingDisasm;
continue;
}
if (!isValidEncoding(EncodingDef)) {
++NumEncodingsOmitted;
continue;
}
Encodings.emplace_back(EncodingDef, &Target.getInstruction(InstDef));
}
// Do some statistics.
NumInstructions = Instructions.size();
NumEncodingsSupported = Encodings.size();
NumEncodings = NumEncodingsSupported + NumEncodingsOmitted;
}
DecoderEmitter::DecoderEmitter(const RecordKeeper &RK,
StringRef PredicateNamespace)
: RK(RK), Target(RK), CGH(Target.getHwModes()),
PredicateNamespace(PredicateNamespace) {
Target.reverseBitsForLittleEndianEncoding();
parseInstructionEncodings();
}
// Emits disassembler code for instruction decoding.
void DecoderEmitter::run(raw_ostream &o) const {
formatted_raw_ostream OS(o);
OS << R"(
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TargetParser/SubtargetFeature.h"
#include <assert.h>
namespace {
)";
// Do extra bookkeeping for variable-length encodings.
std::vector<unsigned> InstrLen;
bool IsVarLenInst = Target.hasVariableLengthEncodings();
unsigned MaxInstLen = 0;
if (IsVarLenInst) {
InstrLen.resize(Target.getInstructions().size(), 0);
for (const InstructionEncoding &Encoding : Encodings) {
MaxInstLen = std::max(MaxInstLen, Encoding.getBitWidth());
InstrLen[Target.getInstrIntValue(Encoding.getInstruction()->TheDef)] =
Encoding.getBitWidth();
}
}
// Map of (namespace, hwmode, size) tuple to encoding IDs.
std::map<std::tuple<StringRef, unsigned, unsigned>, std::vector<unsigned>>
EncMap;
for (const auto &[HwModeID, EncodingIDs] : EncodingIDsByHwMode) {
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
const Record *EncodingDef = Encoding.getRecord();
unsigned Size = EncodingDef->getValueAsInt("Size");
StringRef DecoderNamespace =
EncodingDef->getValueAsString("DecoderNamespace");
EncMap[{DecoderNamespace, HwModeID, Size}].push_back(EncodingID);
}
}
DecoderTableInfo TableInfo;
unsigned OpcodeMask = 0;
for (const auto &[Key, EncodingIDs] : EncMap) {
auto [DecoderNamespace, HwModeID, Size] = Key;
const unsigned BitWidth = IsVarLenInst ? MaxInstLen : 8 * Size;
// Emit the decoder for this (namespace, hwmode, width) combination.
FilterChooser FC(Encodings, EncodingIDs, BitWidth, this);
// The decode table is cleared for each top level decoder function. The
// predicates and decoders themselves, however, are shared across all
// decoders to give more opportunities for uniqueing.
TableInfo.Table.clear();
TableInfo.pushScope();
FC.emitTableEntries(TableInfo);
// Any NumToSkip fixups in the top level scope can resolve to the
// OPC_Fail at the end of the table.
assert(TableInfo.isOutermostScope() && "fixup stack phasing error!");
TableInfo.popScope();
TableInfo.Table.push_back(MCD::OPC_Fail);
// Print the table to the output stream.
OpcodeMask |= emitTable(OS, TableInfo.Table, DecoderNamespace, HwModeID,
BitWidth, EncodingIDs);
}
// For variable instruction, we emit a instruction length table
// to let the decoder know how long the instructions are.
// You can see example usage in M68k's disassembler.
if (IsVarLenInst)
emitInstrLenTable(OS, InstrLen);
const bool HasCheckPredicate =
OpcodeMask &
((1 << MCD::OPC_CheckPredicate) | (1 << MCD::OPC_CheckPredicateOrFail));
// Emit the predicate function.
if (HasCheckPredicate)
emitPredicateFunction(OS, TableInfo.Predicates);
// Emit the decoder function.
emitDecoderFunction(OS, TableInfo.Decoders);
// Emit the main entry point for the decoder, decodeInstruction().
emitDecodeInstruction(OS, IsVarLenInst, OpcodeMask);
OS << "\n} // namespace\n";
}
void llvm::EmitDecoder(const RecordKeeper &RK, raw_ostream &OS,
StringRef PredicateNamespace) {
DecoderEmitter(RK, PredicateNamespace).run(OS);
}
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