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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/CodeGenRegisters.h"
#include "Common/CodeGenTarget.h"
#include "Common/InfoByHwMode.h"
#include "Common/InstructionEncoding.h"
#include "Common/SubtargetFeatureInfo.h"
#include "Common/VarLenCodeEmitterGen.h"
#include "DecoderTableEmitter.h"
#include "DecoderTree.h"
#include "TableGenBackends.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.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/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/KnownBits.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> 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));
// Enabling this option requires use of different `InsnType` for different
// bitwidths and defining `InsnBitWidth` template specialization for the
// `InsnType` types used. Some common specializations are already defined in
// MCDecoder.h.
static cl::opt<bool> SpecializeDecodersPerBitwidth(
"specialize-decoders-per-bitwidth",
cl::desc("Specialize the generated `decodeToMCInst` function per bitwidth. "
"Helps reduce the code size."),
cl::init(false), cl::cat(DisassemblerEmitterCat));
static cl::opt<bool> IgnoreNonDecodableOperands(
"ignore-non-decodable-operands",
cl::desc(
"Do not issue an error if an operand cannot be decoded automatically."),
cl::init(false), cl::cat(DisassemblerEmitterCat));
static cl::opt<bool> IgnoreFullyDefinedOperands(
"ignore-fully-defined-operands",
cl::desc(
"Do not automatically decode operands with no '?' in their encoding."),
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");
/// 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 {
/// Sorting predicate to sort encoding IDs by encoding width.
class LessEncodingIDByWidth {
ArrayRef<InstructionEncoding> Encodings;
public:
explicit LessEncodingIDByWidth(ArrayRef<InstructionEncoding> Encodings)
: Encodings(Encodings) {}
bool operator()(unsigned ID1, unsigned ID2) const {
return Encodings[ID1].getBitWidth() < Encodings[ID2].getBitWidth();
}
};
using NamespacesHwModesMap = std::map<StringRef, 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:
explicit DecoderEmitter(const RecordKeeper &RK);
const CodeGenTarget &getTarget() const { return Target; }
void emitInstrLenTable(formatted_raw_ostream &OS,
ArrayRef<unsigned> InstrLen) const;
void emitPredicateFunction(formatted_raw_ostream &OS,
const PredicateSet &Predicates) const;
void emitRegClassByHwModeDecoders(formatted_raw_ostream &OS) const;
void emitDecoderFunction(formatted_raw_ostream &OS,
const DecoderSet &Decoders,
unsigned BucketBitWidth) 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();
};
struct EncodingIsland {
unsigned StartBit;
unsigned NumBits;
uint64_t FieldVal;
};
/// 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.
struct 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;
Filter(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs, unsigned StartBit, unsigned NumBits);
// 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 {
// TODO: Unfriend by providing the necessary accessors.
friend class DecoderTreeBuilder;
// Vector of encodings to choose our filter.
ArrayRef<InstructionEncoding> Encodings;
/// Encoding IDs for this filter chooser to work on.
/// Sorted by non-decreasing encoding width.
SmallVector<unsigned, 0> EncodingIDs;
// 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;
/// If the selected filter matches multiple encodings, then this is the
/// starting position and the width of the filtered range.
unsigned StartBit;
unsigned NumBits;
/// If the selected filter matches multiple encodings, and there is
/// *exactly one* encoding in which all bits are known in the filtered range,
/// then this is the ID of that encoding.
/// Also used when there is only one encoding.
std::optional<unsigned> SingletonEncodingID;
/// If the selected filter matches multiple encodings, and there is
/// *at least one* encoding in which all bits are known in the filtered range,
/// then this is the FilterChooser created for the subset of encodings that
/// contain some unknown bits in the filtered range.
std::unique_ptr<const FilterChooser> VariableFC;
/// If the selected filter matches multiple encodings, and there is
/// *more than one* encoding in which all bits are known in the filtered
/// range, then this is a map of field values to FilterChoosers created for
/// the subset of encodings sharing that field value.
/// The "field value" here refers to the encoding bits in the filtered range.
std::map<uint64_t, std::unique_ptr<const FilterChooser>> FilterChooserMap;
/// Set to true if decoding conflict was encountered.
bool HasConflict = false;
public:
/// Constructs a top-level filter chooser.
FilterChooser(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs)
: Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr) {
// Sort encoding IDs once.
stable_sort(this->EncodingIDs, LessEncodingIDByWidth(Encodings));
// Filter width is the width of the smallest encoding.
unsigned FilterWidth = Encodings[this->EncodingIDs.front()].getBitWidth();
FilterBits = KnownBits(FilterWidth);
doFilter();
}
/// Constructs an inferior filter chooser.
FilterChooser(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs, const KnownBits &FilterBits,
const FilterChooser &Parent)
: Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(&Parent) {
// Inferior filter choosers are created from sorted array of encoding IDs.
assert(is_sorted(EncodingIDs, LessEncodingIDByWidth(Encodings)));
assert(!FilterBits.hasConflict() && "Broken filter");
// Filter width is the width of the smallest encoding.
unsigned FilterWidth = Encodings[EncodingIDs.front()].getBitWidth();
this->FilterBits = FilterBits.anyext(FilterWidth);
doFilter();
}
FilterChooser(const FilterChooser &) = delete;
void operator=(const FilterChooser &) = delete;
/// Returns the width of the largest encoding.
unsigned getMaxEncodingWidth() const {
// The last encoding ID is the ID of an encoding with the largest width.
return Encodings[EncodingIDs.back()].getBitWidth();
}
/// Returns true if any decoding conflicts were encountered.
bool hasConflict() const { return HasConflict; }
private:
/// Applies the given filter to the set of encodings this FilterChooser
/// works with, creating inferior FilterChoosers as necessary.
void applyFilter(const Filter &F);
/// dumpStack - dumpStack traverses the filter chooser chain and calls
/// dumpFilterArray on each filter chooser up to the top level one.
void dumpStack(raw_ostream &OS, indent Indent, unsigned PadToWidth) const;
bool isPositionFiltered(unsigned Idx) const {
return FilterBits.Zero[Idx] || FilterBits.One[Idx];
}
/// Scans the well-known encoding bits of the encodings and, builds up a list
/// of candidate filters, and then returns the best one, if any.
std::unique_ptr<Filter> findBestFilter(ArrayRef<bitAttr_t> BitAttrs,
bool AllowMixed,
bool Greedy = true) const;
std::unique_ptr<Filter> findBestFilter() const;
// 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:
void dump() const;
};
} // end anonymous namespace
///////////////////////////
// //
// Filter Implementation //
// //
///////////////////////////
Filter::Filter(ArrayRef<InstructionEncoding> Encodings,
ArrayRef<unsigned> EncodingIDs, unsigned StartBit,
unsigned NumBits)
: StartBit(StartBit), NumBits(NumBits) {
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();
// 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");
}
void FilterChooser::applyFilter(const Filter &F) {
StartBit = F.StartBit;
NumBits = F.NumBits;
assert(FilterBits.extractBits(NumBits, StartBit).isUnknown());
if (!F.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>(Encodings, F.VariableIDs,
FilterBits, *this);
HasConflict |= VariableFC->HasConflict;
}
// Otherwise, create sub choosers.
for (const auto &[FilterVal, InferiorEncodingIDs] : F.FilteredIDs) {
// Create a new filter by inserting the field bits into the parent filter.
APInt FieldBits(NumBits, FilterVal);
KnownBits InferiorFilterBits = FilterBits;
InferiorFilterBits.insertBits(KnownBits::makeConstant(FieldBits), StartBit);
// Delegates to an inferior filter chooser for further processing on this
// category of instructions.
auto [It, _] = FilterChooserMap.try_emplace(
FilterVal,
std::make_unique<FilterChooser>(Encodings, InferiorEncodingIDs,
InferiorFilterBits, *this));
HasConflict |= It->second->HasConflict;
}
}
// 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 //
// //
//////////////////////////////////
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, const 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 "
"&FB) {\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";
}
/// Emit a default implementation of a decoder for all RegClassByHwModes which
/// do not have an explicit DecoderMethodSet, which dispatches over the decoder
/// methods for the member classes.
void DecoderEmitter::emitRegClassByHwModeDecoders(
formatted_raw_ostream &OS) const {
const CodeGenHwModes &CGH = Target.getHwModes();
if (CGH.getNumModeIds() == 1)
return;
ArrayRef<const Record *> RegClassByHwMode = Target.getAllRegClassByHwMode();
if (RegClassByHwMode.empty())
return;
for (const Record *ClassByHwMode : RegClassByHwMode) {
// Ignore cases that had an explicit DecoderMethod set.
if (!InstructionEncoding::findOperandDecoderMethod(ClassByHwMode).second)
continue;
const HwModeSelect &ModeSelect = CGH.getHwModeSelect(ClassByHwMode);
// Mips has a system where this is only used by compound operands with
// custom decoders, and we don't try to detect if this decoder is really
// needed.
OS << "[[maybe_unused]]\n";
OS << "static DecodeStatus Decode" << ClassByHwMode->getName()
<< "RegClassByHwMode";
OS << R"((MCInst &Inst, unsigned Imm, uint64_t Addr, const MCDisassembler *Decoder) {
switch (Decoder->getSubtargetInfo().getHwMode(MCSubtargetInfo::HwMode_RegInfo)) {
)";
for (auto [ModeID, RegClassRec] : ModeSelect.Items) {
OS << indent(2) << "case " << ModeID << ": // "
<< CGH.getModeName(ModeID, /*IncludeDefault=*/true) << '\n'
<< indent(4) << "return "
<< InstructionEncoding::findOperandDecoderMethod(RegClassRec).first
<< "(Inst, Imm, Addr, Decoder);\n";
}
OS << indent(2) << R"(default:
llvm_unreachable("no decoder for hwmode");
}
}
)";
}
OS << '\n';
}
void DecoderEmitter::emitDecoderFunction(formatted_raw_ostream &OS,
const DecoderSet &Decoders,
unsigned BucketBitWidth) 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";
// Print the name of the decode function to OS.
auto PrintDecodeFnName = [&OS, BucketBitWidth](unsigned DecodeIdx) {
OS << "decodeFn";
if (BucketBitWidth != 0) {
OS << '_' << BucketBitWidth << "bit";
}
OS << '_' << DecodeIdx;
};
// Print the template statement.
auto PrintTemplate = [&OS, BucketBitWidth]() {
OS << "template <typename InsnType>\n";
OS << "static ";
if (BucketBitWidth != 0)
OS << "std::enable_if_t<InsnBitWidth<InsnType> == " << BucketBitWidth
<< ", DecodeStatus>\n";
else
OS << "DecodeStatus ";
};
if (UseFnTableInDecodeToMCInst) {
// Emit a function for each case first.
for (const auto &[Index, Decoder] : enumerate(Decoders)) {
PrintTemplate();
PrintDecodeFnName(Index);
OS << "(" << DecodeParams << ") {\n";
OS << " " << TmpTypeDecl;
OS << " [[maybe_unused]] TmpType tmp;\n";
OS << Decoder;
OS << " return S;\n";
OS << "}\n\n";
}
}
OS << "// Handling " << Decoders.size() << " cases.\n";
PrintTemplate();
OS << "decodeToMCInst(unsigned Idx, " << DecodeParams << ") {\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 << " ";
PrintDecodeFnName(Index);
OS << ",\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,
unsigned PadToWidth) const {
if (Parent)
Parent->dumpStack(OS, Indent, PadToWidth);
assert(PadToWidth >= FilterBits.getBitWidth());
OS << Indent << indent(PadToWidth - FilterBits.getBitWidth());
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.
static std::vector<EncodingIsland> getIslands(const KnownBits &EncodingBits,
const KnownBits &FilterBits) {
std::vector<EncodingIsland> Islands;
uint64_t FieldVal;
unsigned StartBit;
bool OnIsland = false;
unsigned FilterWidth = FilterBits.getBitWidth();
for (unsigned I = 0; I != FilterWidth; ++I) {
bool IsKnown = EncodingBits.Zero[I] || EncodingBits.One[I];
bool IsFiltered = FilterBits.Zero[I] || FilterBits.One[I];
if (!IsFiltered && IsKnown) {
if (OnIsland) {
// Accumulate island bits.
FieldVal |= static_cast<uint64_t>(EncodingBits.One[I])
<< (I - StartBit);
} else {
// Onto an island.
StartBit = I;
FieldVal = static_cast<uint64_t>(EncodingBits.One[I]);
OnIsland = true;
}
} else if (OnIsland) {
// Into the water.
Islands.push_back({StartBit, I - StartBit, FieldVal});
OnIsland = false;
}
}
if (OnIsland)
Islands.push_back({StartBit, FilterWidth - StartBit, FieldVal});
return Islands;
}
static void emitBinaryParser(raw_ostream &OS, indent Indent,
const InstructionEncoding &Encoding,
const OperandInfo &OpInfo) {
if (OpInfo.HasNoEncoding) {
// If an operand has no encoding, the old behavior is to not decode it
// automatically and let the target do it. This is error-prone, so the
// new behavior is to report an error.
if (!IgnoreNonDecodableOperands)
PrintError(Encoding.getRecord()->getLoc(),
"could not find field for operand '" + OpInfo.Name + "'");
return;
}
// Special case for 'bits<0>'.
if (OpInfo.Fields.empty() && !OpInfo.InitValue) {
assert(!OpInfo.Decoder.empty());
// The operand has no encoding, so the corresponding argument is omitted.
// This avoids confusion and allows the function to be overloaded if the
// operand does have an encoding in other instructions.
OS << Indent << "if (!Check(S, " << OpInfo.Decoder << "(MI, Decoder)))\n"
<< Indent << " return MCDisassembler::Fail;\n";
return;
}
if (OpInfo.fields().empty()) {
// Only a constant part. The old behavior is to not decode this operand.
if (IgnoreFullyDefinedOperands)
return;
// Initialize `tmp` with the constant part.
OS << Indent << "tmp = " << format_hex(*OpInfo.InitValue, 0) << ";\n";
} else if (OpInfo.fields().size() == 1 && !OpInfo.InitValue.value_or(0)) {
// One variable part and no/zero constant part. Initialize `tmp` with the
// variable part.
auto [Base, Width, Offset] = OpInfo.fields().front();
OS << Indent << "tmp = fieldFromInstruction(insn, " << Base << ", " << Width
<< ')';
if (Offset)
OS << " << " << Offset;
OS << ";\n";
} else {
// General case. Initialize `tmp` with the constant part, if any, and
// insert the variable parts into it.
OS << Indent << "tmp = " << format_hex(OpInfo.InitValue.value_or(0), 0)
<< ";\n";
for (auto [Base, Width, Offset] : OpInfo.fields()) {
OS << Indent << "tmp |= fieldFromInstruction(insn, " << Base << ", "
<< Width << ')';
if (Offset)
OS << " << " << Offset;
OS << ";\n";
}
}
StringRef Decoder = OpInfo.Decoder;
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";
}
}
static std::string getDecoderString(const InstructionEncoding &Encoding) {
std::string Decoder;
raw_string_ostream OS(Decoder);
indent Indent(UseFnTableInDecodeToMCInst ? 2 : 4);
// 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";
} else {
for (const OperandInfo &Op : Encoding.getOperands())
emitBinaryParser(OS, Indent, Encoding, Op);
}
return Decoder;
}
static std::string getPredicateString(const InstructionEncoding &Encoding,
StringRef TargetName) {
std::vector<const Record *> Predicates =
Encoding.getRecord()->getValueAsListOfDefs("Predicates");
auto It = llvm::find_if(Predicates, [](const Record *R) {
return R->getValueAsBit("AssemblerMatcherPredicate");
});
if (It == Predicates.end())
return std::string();
std::string Predicate;
raw_string_ostream OS(Predicate);
SubtargetFeatureInfo::emitMCPredicateCheck(OS, TargetName, Predicates);
return Predicate;
}
std::unique_ptr<Filter>
FilterChooser::findBestFilter(ArrayRef<bitAttr_t> BitAttrs, bool AllowMixed,
bool Greedy) const {
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) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();
// Look for islands of undecoded bits of any instruction.
std::vector<EncodingIsland> Islands =
getIslands(EncodingBits, FilterBits);
if (!Islands.empty()) {
// Found an instruction with island(s). Now just assign a filter.
return std::make_unique<Filter>(
Encodings, EncodingIDs, Islands[0].StartBit, Islands[0].NumBits);
}
}
}
// 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;
auto addCandidateFilter = [&](unsigned StartBit, unsigned EndBit) {
Filters.push_back(std::make_unique<Filter>(Encodings, EncodingIDs, StartBit,
EndBit - StartBit));
};
unsigned FilterWidth = FilterBits.getBitWidth();
for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++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:
if (!AllowMixed && bitAttr != ATTR_ALL_SET)
addCandidateFilter(StartBit, BitIndex);
switch (bitAttr) {
case ATTR_FILTERED:
RA = ATTR_NONE;
break;
case ATTR_ALL_SET:
break;
case ATTR_ALL_UNSET:
RA = ATTR_NONE;
break;
case ATTR_MIXED:
StartBit = BitIndex;
RA = ATTR_MIXED;
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_MIXED:
if (AllowMixed && bitAttr != ATTR_MIXED)
addCandidateFilter(StartBit, BitIndex);
switch (bitAttr) {
case ATTR_FILTERED:
StartBit = BitIndex;
RA = ATTR_NONE;
break;
case ATTR_ALL_SET:
StartBit = BitIndex;
RA = ATTR_ALL_SET;
break;
case ATTR_ALL_UNSET:
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:
if (!AllowMixed)
addCandidateFilter(StartBit, FilterWidth);
break;
case ATTR_ALL_UNSET:
break;
case ATTR_MIXED:
if (AllowMixed)
addCandidateFilter(StartBit, FilterWidth);
break;
}
// We have finished with the filter processings. Now it's time to choose
// the best performing filter.
auto MaxIt = llvm::max_element(Filters, [](const std::unique_ptr<Filter> &A,
const std::unique_ptr<Filter> &B) {
return A->usefulness() < B->usefulness();
});
if (MaxIt == Filters.end() || (*MaxIt)->usefulness() == 0)
return nullptr;
return std::move(*MaxIt);
}
std::unique_ptr<Filter> FilterChooser::findBestFilter() const {
// 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)
unsigned FilterWidth = FilterBits.getBitWidth();
SmallVector<bitAttr_t, 128> BitAttrs(FilterWidth, 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 != FilterWidth; ++BitIndex)
if (isPositionFiltered(BitIndex))
BitAttrs[BitIndex] = ATTR_FILTERED;
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
KnownBits EncodingBits = Encoding.getMandatoryBits();
for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++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 (std::unique_ptr<Filter> F =
findBestFilter(BitAttrs, /*AllowMixed=*/false))
return F;
// Then regions of mixed bits (both known and unitialized bit values allowed).
if (std::unique_ptr<Filter> F = findBestFilter(BitAttrs, /*AllowMixed=*/true))
return F;
// 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) {
if (std::unique_ptr<Filter> F =
findBestFilter(BitAttrs, /*AllowMixed=*/true, /*Greedy=*/false))
return F;
}
// There is a conflict we could not resolve.
return nullptr;
}
// 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() == 1) {
SingletonEncodingID = EncodingIDs.front();
return;
}
std::unique_ptr<Filter> BestFilter = findBestFilter();
if (BestFilter) {
applyFilter(*BestFilter);
return;
}
// Print out useful conflict information for postmortem analysis.
errs() << "Decoding Conflict:\n";
dump();
HasConflict = true;
}
void FilterChooser::dump() const {
indent Indent(4);
// Helps to keep the output right-justified.
unsigned PadToWidth = getMaxEncodingWidth();
// Dump filter stack.
dumpStack(errs(), Indent, PadToWidth);
// Dump encodings.
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
errs() << Indent << indent(PadToWidth - Encoding.getBitWidth());
printKnownBits(errs(), Encoding.getMandatoryBits(), '_');
errs() << " " << Encoding.getName() << '\n';
}
}
// emitDecodeInstruction - Emit the templated helper function
// decodeInstruction().
static void emitDecodeInstruction(formatted_raw_ostream &OS, bool IsVarLenInst,
const DecoderTableInfo &TableInfo) {
OS << R"(
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 (TableInfo.HasCheckPredicate)
OS << " const FeatureBitset &Bits = STI.getFeatureBits();\n";
OS << " const uint8_t *Ptr = DecodeTable;\n";
if (SpecializeDecodersPerBitwidth) {
// Fail with a fatal error if decoder table's bitwidth does not match
// `InsnType` bitwidth.
OS << R"(
[[maybe_unused]] uint32_t BitWidth = decodeULEB128AndIncUnsafe(Ptr);
assert(InsnBitWidth<InsnType> == BitWidth &&
"Table and instruction bitwidth mismatch");
)";
}
OS << R"(
SmallVector<const uint8_t *, 8> ScopeStack;
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 OPC_Scope: {
unsigned NumToSkip = decodeULEB128AndIncUnsafe(Ptr);
const uint8_t *SkipTo = Ptr + NumToSkip;
ScopeStack.push_back(SkipTo);
LLVM_DEBUG(dbgs() << Loc << ": OPC_Scope(" << SkipTo - DecodeTable
<< ")\n");
continue;
}
case OPC_SwitchField: {
// 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);
uint64_t CaseValue;
unsigned CaseSize;
while (true) {
CaseValue = decodeULEB128AndIncUnsafe(Ptr);
CaseSize = decodeULEB128AndIncUnsafe(Ptr);
if (FieldValue == CaseValue || !CaseSize)
break;
Ptr += CaseSize;
}
if (FieldValue == CaseValue) {
LLVM_DEBUG(dbgs() << Loc << ": OPC_SwitchField(" << Start << ", " << Len
<< "): " << FieldValue << '\n');
continue;
}
break;
}
case OPC_CheckField: {
// 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;
LLVM_DEBUG(dbgs() << Loc << ": OPC_CheckField(" << Start << ", " << Len
<< ", " << ExpectedValue << "): FieldValue = "
<< FieldValue << ", ExpectedValue = " << ExpectedValue
<< ": " << (Failed ? "FAIL, " : "PASS\n"););
if (!Failed)
continue;
break;
})";
if (TableInfo.HasCheckPredicate) {
OS << R"(
case OPC_CheckPredicate: {
// Decode the Predicate Index value.
unsigned PIdx = decodeULEB128AndIncUnsafe(Ptr);
// Check the predicate.
bool Failed = !checkDecoderPredicate(PIdx, Bits);
LLVM_DEBUG(dbgs() << Loc << ": OPC_CheckPredicate(" << PIdx << "): "
<< (Failed ? "FAIL, " : "PASS\n"););
if (!Failed)
continue;
break;
})";
}
OS << R"(
case 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);
LLVM_DEBUG(dbgs() << Loc << ": OPC_Decode: opcode " << Opc
<< ", using decoder " << DecodeIdx << ": "
<< (S ? "PASS, " : "FAIL, "));
if (DecodeComplete) {
LLVM_DEBUG(dbgs() << "decoding complete\n");
return S;
}
assert(S == MCDisassembler::Fail);
// Reset decode status. This also drops a SoftFail status that could be
// set before the decode attempt.
S = MCDisassembler::Success;
break;
})";
if (TableInfo.HasSoftFail) {
OS << R"(
case 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"));
continue;
})";
}
OS << R"(
}
if (ScopeStack.empty()) {
LLVM_DEBUG(dbgs() << "returning Fail\n");
return MCDisassembler::Fail;
}
Ptr = ScopeStack.pop_back_val();
LLVM_DEBUG(dbgs() << "continuing at " << Ptr - DecodeTable << '\n');
}
llvm_unreachable("bogosity detected in disassembler state machine!");
}
)";
}
namespace {
class DecoderTreeBuilder {
DecoderContext &Ctx;
const CodeGenTarget &Target;
ArrayRef<InstructionEncoding> Encodings;
public:
DecoderTreeBuilder(DecoderContext &Ctx, const CodeGenTarget &Target,
ArrayRef<InstructionEncoding> Encodings)
: Ctx(Ctx), Target(Target), Encodings(Encodings) {}
std::unique_ptr<DecoderTreeNode> buildTree(ArrayRef<unsigned> EncodingIDs);
private:
std::unique_ptr<DecoderTreeNode>
convertSingleton(unsigned EncodingID, const KnownBits &FilterBits);
std::unique_ptr<DecoderTreeNode> convertFilterChooserMap(
unsigned StartBit, unsigned NumBits,
const std::map<uint64_t, std::unique_ptr<const FilterChooser>> &FCMap);
std::unique_ptr<DecoderTreeNode>
convertFilterChooser(const FilterChooser *FC);
};
} // namespace
std::unique_ptr<DecoderTreeNode>
DecoderTreeBuilder::convertSingleton(unsigned EncodingID,
const KnownBits &FilterBits) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
auto N = std::make_unique<CheckAllNode>();
std::string Predicate = getPredicateString(Encoding, Target.getName());
if (!Predicate.empty()) {
unsigned PredicateIndex = Ctx.getPredicateIndex(Predicate);
N->addChild(std::make_unique<CheckPredicateNode>(PredicateIndex));
}
std::vector<EncodingIsland> Islands =
getIslands(Encoding.getMandatoryBits(), FilterBits);
for (const EncodingIsland &Island : reverse(Islands)) {
N->addChild(std::make_unique<CheckFieldNode>(
Island.StartBit, Island.NumBits, Island.FieldVal));
}
const KnownBits &InstBits = Encoding.getInstBits();
const APInt &SoftFailMask = Encoding.getSoftFailMask();
if (!SoftFailMask.isZero()) {
APInt PositiveMask = InstBits.Zero & SoftFailMask;
APInt NegativeMask = InstBits.One & SoftFailMask;
N->addChild(std::make_unique<SoftFailNode>(PositiveMask.getZExtValue(),
NegativeMask.getZExtValue()));
}
unsigned DecoderIndex = Ctx.getDecoderIndex(getDecoderString(Encoding));
N->addChild(std::make_unique<DecodeNode>(
Encoding.getName(), Encoding.getInstruction()->EnumVal, DecoderIndex));
return N;
}
std::unique_ptr<DecoderTreeNode> DecoderTreeBuilder::convertFilterChooserMap(
unsigned StartBit, unsigned NumBits,
const std::map<uint64_t, std::unique_ptr<const FilterChooser>> &FCMap) {
if (FCMap.size() == 1) {
const auto &[FieldVal, ChildFC] = *FCMap.begin();
auto N = std::make_unique<CheckAllNode>();
N->addChild(std::make_unique<CheckFieldNode>(StartBit, NumBits, FieldVal));
N->addChild(convertFilterChooser(ChildFC.get()));
return N;
}
auto N = std::make_unique<SwitchFieldNode>(StartBit, NumBits);
for (const auto &[FieldVal, ChildFC] : FCMap)
N->addCase(FieldVal, convertFilterChooser(ChildFC.get()));
return N;
}
std::unique_ptr<DecoderTreeNode>
DecoderTreeBuilder::convertFilterChooser(const FilterChooser *FC) {
auto N = std::make_unique<CheckAnyNode>();
do {
if (FC->SingletonEncodingID)
N->addChild(convertSingleton(*FC->SingletonEncodingID, FC->FilterBits));
else
N->addChild(convertFilterChooserMap(FC->StartBit, FC->NumBits,
FC->FilterChooserMap));
FC = FC->VariableFC.get();
} while (FC);
return N;
}
std::unique_ptr<DecoderTreeNode>
DecoderTreeBuilder::buildTree(ArrayRef<unsigned> EncodingIDs) {
FilterChooser FC(Encodings, EncodingIDs);
if (FC.hasConflict())
return nullptr;
return convertFilterChooser(&FC);
}
/// 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")) {
StringRef DecoderNamespace =
EncodingDef->getValueAsString("DecoderNamespace");
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: {
StringRef DecoderNamespace = Encodings[EncodingID].getDecoderNamespace();
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;
}
unsigned EncodingID = Encodings.size();
Encodings.emplace_back(EncodingDef, &Target.getInstruction(InstDef));
EncodingIDsByHwMode[DefaultMode].push_back(EncodingID);
}
// Do some statistics.
NumInstructions = Instructions.size();
NumEncodingsSupported = Encodings.size();
NumEncodings = NumEncodingsSupported + NumEncodingsOmitted;
}
DecoderEmitter::DecoderEmitter(const RecordKeeper &RK)
: RK(RK), Target(RK), CGH(Target.getHwModes()) {
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 {
// InsnBitWidth is essentially a type trait used by the decoder emitter to query
// the supported bitwidth for a given type. But default, the value is 0, making
// it an invalid type for use as `InsnType` when instantiating the decoder.
// Individual targets are expected to provide specializations for these based
// on their usage.
template <typename T> constexpr uint32_t InsnBitWidth = 0;
)";
// Do extra bookkeeping for variable-length encodings.
bool IsVarLenInst = Target.hasVariableLengthEncodings();
unsigned MaxInstLen = 0;
if (IsVarLenInst) {
std::vector<unsigned> InstrLen(Target.getInstructions().size(), 0);
for (const InstructionEncoding &Encoding : Encodings) {
MaxInstLen = std::max(MaxInstLen, Encoding.getBitWidth());
InstrLen[Target.getInstrIntValue(Encoding.getInstruction()->TheDef)] =
Encoding.getBitWidth();
}
// For variable instruction, we emit an instruction length table to let the
// decoder know how long the instructions are. You can see example usage in
// M68k's disassembler.
emitInstrLenTable(OS, InstrLen);
}
emitRegClassByHwModeDecoders(OS);
// Map of (bitwidth, namespace, hwmode) tuple to encoding IDs.
// Its organized as a nested map, with the (namespace, hwmode) as the key for
// the inner map and bitwidth as the key for the outer map. We use std::map
// for deterministic iteration order so that the code emitted is also
// deterministic.
using InnerKeyTy = std::pair<StringRef, unsigned>;
using InnerMapTy = std::map<InnerKeyTy, std::vector<unsigned>>;
std::map<unsigned, InnerMapTy> EncMap;
for (const auto &[HwModeID, EncodingIDs] : EncodingIDsByHwMode) {
for (unsigned EncodingID : EncodingIDs) {
const InstructionEncoding &Encoding = Encodings[EncodingID];
const unsigned BitWidth =
IsVarLenInst ? MaxInstLen : Encoding.getBitWidth();
StringRef DecoderNamespace = Encoding.getDecoderNamespace();
EncMap[BitWidth][{DecoderNamespace, HwModeID}].push_back(EncodingID);
}
}
// Variable length instructions use the same `APInt` type for all instructions
// so we cannot specialize decoders based on instruction bitwidths (which
// requires using different `InstType` for differet bitwidths for the correct
// template specialization to kick in).
if (IsVarLenInst && SpecializeDecodersPerBitwidth)
PrintFatalError(
"Cannot specialize decoders for variable length instuctions");
DecoderContext Ctx;
DecoderTreeBuilder TreeBuilder(Ctx, Target, Encodings);
DecoderTableInfo TableInfo;
DecoderTableEmitter TableEmitter(TableInfo, OS);
// Emit a table for each (namespace, hwmode, bitwidth) combination.
// Entries in `EncMap` are already sorted by bitwidth. So bucketing per
// bitwidth can be done on-the-fly as we iterate over the map.
bool HasConflict = false;
for (const auto &[BitWidth, BWMap] : EncMap) {
for (const auto &[Key, EncodingIDs] : BWMap) {
auto [DecoderNamespace, HwModeID] = Key;
std::unique_ptr<DecoderTreeNode> Tree =
TreeBuilder.buildTree(EncodingIDs);
// Skip emitting the table if a conflict has been detected.
if (!Tree) {
HasConflict = true;
continue;
}
// Form the table name.
SmallString<32> TableName({"DecoderTable", DecoderNamespace});
if (HwModeID != DefaultMode)
TableName.append({"_", Target.getHwModes().getModeName(HwModeID)});
TableName.append(utostr(BitWidth));
TableEmitter.emitTable(
TableName, SpecializeDecodersPerBitwidth ? BitWidth : 0, Tree.get());
}
// Each BitWidth get's its own decoders and decoder function if
// SpecializeDecodersPerBitwidth is enabled.
if (SpecializeDecodersPerBitwidth) {
emitDecoderFunction(OS, Ctx.Decoders, BitWidth);
Ctx.Decoders.clear();
}
}
if (HasConflict)
PrintFatalError("Decoding conflict encountered");
// Emit the decoder function for the last bucket. This will also emit the
// single decoder function if SpecializeDecodersPerBitwidth = false.
if (!SpecializeDecodersPerBitwidth)
emitDecoderFunction(OS, Ctx.Decoders, 0);
// Emit the predicate function.
if (TableInfo.HasCheckPredicate)
emitPredicateFunction(OS, Ctx.Predicates);
// Emit the main entry point for the decoder, decodeInstruction().
emitDecodeInstruction(OS, IsVarLenInst, TableInfo);
OS << "\n} // namespace\n";
}
void llvm::EmitDecoder(const RecordKeeper &RK, raw_ostream &OS) {
DecoderEmitter(RK).run(OS);
}