1624 lines · cpp
1//===---------------- DecoderEmitter.cpp - Decoder Generator --------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// It contains the tablegen backend that emits the decoder functions for10// targets with fixed/variable length instruction set.11//12//===----------------------------------------------------------------------===//13 14#include "Common/CodeGenHwModes.h"15#include "Common/CodeGenInstruction.h"16#include "Common/CodeGenRegisters.h"17#include "Common/CodeGenTarget.h"18#include "Common/InfoByHwMode.h"19#include "Common/InstructionEncoding.h"20#include "Common/SubtargetFeatureInfo.h"21#include "Common/VarLenCodeEmitterGen.h"22#include "DecoderTableEmitter.h"23#include "DecoderTree.h"24#include "TableGenBackends.h"25#include "llvm/ADT/APInt.h"26#include "llvm/ADT/ArrayRef.h"27#include "llvm/ADT/STLExtras.h"28#include "llvm/ADT/SetVector.h"29#include "llvm/ADT/SmallBitVector.h"30#include "llvm/ADT/SmallString.h"31#include "llvm/ADT/Statistic.h"32#include "llvm/ADT/StringExtras.h"33#include "llvm/ADT/StringRef.h"34#include "llvm/Support/Casting.h"35#include "llvm/Support/CommandLine.h"36#include "llvm/Support/Debug.h"37#include "llvm/Support/ErrorHandling.h"38#include "llvm/Support/Format.h"39#include "llvm/Support/FormatVariadic.h"40#include "llvm/Support/FormattedStream.h"41#include "llvm/Support/KnownBits.h"42#include "llvm/Support/MathExtras.h"43#include "llvm/Support/raw_ostream.h"44#include "llvm/TableGen/Error.h"45#include "llvm/TableGen/Record.h"46#include <algorithm>47#include <cassert>48#include <cstddef>49#include <cstdint>50#include <map>51#include <memory>52#include <set>53#include <string>54#include <utility>55#include <vector>56 57using namespace llvm;58 59#define DEBUG_TYPE "decoder-emitter"60 61extern cl::OptionCategory DisassemblerEmitterCat;62 63enum SuppressLevel {64 SUPPRESSION_DISABLE,65 SUPPRESSION_LEVEL1,66 SUPPRESSION_LEVEL267};68 69static cl::opt<SuppressLevel> DecoderEmitterSuppressDuplicates(70 "suppress-per-hwmode-duplicates",71 cl::desc("Suppress duplication of instrs into per-HwMode decoder tables"),72 cl::values(73 clEnumValN(74 SUPPRESSION_DISABLE, "O0",75 "Do not prevent DecoderTable duplications caused by HwModes"),76 clEnumValN(77 SUPPRESSION_LEVEL1, "O1",78 "Remove duplicate DecoderTable entries generated due to HwModes"),79 clEnumValN(80 SUPPRESSION_LEVEL2, "O2",81 "Extract HwModes-specific instructions into new DecoderTables, "82 "significantly reducing Table Duplications")),83 cl::init(SUPPRESSION_DISABLE), cl::cat(DisassemblerEmitterCat));84 85static cl::opt<bool> UseFnTableInDecodeToMCInst(86 "use-fn-table-in-decode-to-mcinst",87 cl::desc(88 "Use a table of function pointers instead of a switch case in the\n"89 "generated `decodeToMCInst` function. Helps improve compile time\n"90 "of the generated code."),91 cl::init(false), cl::cat(DisassemblerEmitterCat));92 93// Enabling this option requires use of different `InsnType` for different94// bitwidths and defining `InsnBitWidth` template specialization for the95// `InsnType` types used. Some common specializations are already defined in96// MCDecoder.h.97static cl::opt<bool> SpecializeDecodersPerBitwidth(98 "specialize-decoders-per-bitwidth",99 cl::desc("Specialize the generated `decodeToMCInst` function per bitwidth. "100 "Helps reduce the code size."),101 cl::init(false), cl::cat(DisassemblerEmitterCat));102 103static cl::opt<bool> IgnoreNonDecodableOperands(104 "ignore-non-decodable-operands",105 cl::desc(106 "Do not issue an error if an operand cannot be decoded automatically."),107 cl::init(false), cl::cat(DisassemblerEmitterCat));108 109static cl::opt<bool> IgnoreFullyDefinedOperands(110 "ignore-fully-defined-operands",111 cl::desc(112 "Do not automatically decode operands with no '?' in their encoding."),113 cl::init(false), cl::cat(DisassemblerEmitterCat));114 115STATISTIC(NumEncodings, "Number of encodings considered");116STATISTIC(NumEncodingsLackingDisasm,117 "Number of encodings without disassembler info");118STATISTIC(NumInstructions, "Number of instructions considered");119STATISTIC(NumEncodingsSupported, "Number of encodings supported");120STATISTIC(NumEncodingsOmitted, "Number of encodings omitted");121 122/// Similar to KnownBits::print(), but allows you to specify a character to use123/// to print unknown bits.124static void printKnownBits(raw_ostream &OS, const KnownBits &Bits,125 char Unknown) {126 for (unsigned I = Bits.getBitWidth(); I--;) {127 if (Bits.Zero[I] && Bits.One[I])128 OS << '!';129 else if (Bits.Zero[I])130 OS << '0';131 else if (Bits.One[I])132 OS << '1';133 else134 OS << Unknown;135 }136}137 138namespace {139 140/// Sorting predicate to sort encoding IDs by encoding width.141class LessEncodingIDByWidth {142 ArrayRef<InstructionEncoding> Encodings;143 144public:145 explicit LessEncodingIDByWidth(ArrayRef<InstructionEncoding> Encodings)146 : Encodings(Encodings) {}147 148 bool operator()(unsigned ID1, unsigned ID2) const {149 return Encodings[ID1].getBitWidth() < Encodings[ID2].getBitWidth();150 }151};152 153using NamespacesHwModesMap = std::map<StringRef, std::set<unsigned>>;154 155class DecoderEmitter {156 const RecordKeeper &RK;157 CodeGenTarget Target;158 const CodeGenHwModes &CGH;159 160 /// All parsed encodings.161 std::vector<InstructionEncoding> Encodings;162 163 /// Encodings IDs for each HwMode. An ID is an index into Encodings.164 SmallDenseMap<unsigned, std::vector<unsigned>> EncodingIDsByHwMode;165 166public:167 explicit DecoderEmitter(const RecordKeeper &RK);168 169 const CodeGenTarget &getTarget() const { return Target; }170 171 void emitInstrLenTable(formatted_raw_ostream &OS,172 ArrayRef<unsigned> InstrLen) const;173 void emitPredicateFunction(formatted_raw_ostream &OS,174 const PredicateSet &Predicates) const;175 176 void emitRegClassByHwModeDecoders(formatted_raw_ostream &OS) const;177 void emitDecoderFunction(formatted_raw_ostream &OS,178 const DecoderSet &Decoders,179 unsigned BucketBitWidth) const;180 181 // run - Output the code emitter182 void run(raw_ostream &o) const;183 184private:185 void collectHwModesReferencedForEncodings(186 std::vector<unsigned> &HwModeIDs,187 NamespacesHwModesMap &NamespacesWithHwModes) const;188 189 void190 handleHwModesUnrelatedEncodings(unsigned EncodingID,191 ArrayRef<unsigned> HwModeIDs,192 NamespacesHwModesMap &NamespacesWithHwModes);193 194 void parseInstructionEncodings();195};196 197struct EncodingIsland {198 unsigned StartBit;199 unsigned NumBits;200 uint64_t FieldVal;201};202 203/// Filter - Filter works with FilterChooser to produce the decoding tree for204/// the ISA.205///206/// It is useful to think of a Filter as governing the switch stmts of the207/// decoding tree in a certain level. Each case stmt delegates to an inferior208/// FilterChooser to decide what further decoding logic to employ, or in another209/// words, what other remaining bits to look at. The FilterChooser eventually210/// chooses a best Filter to do its job.211///212/// This recursive scheme ends when the number of Opcodes assigned to the213/// FilterChooser becomes 1 or if there is a conflict. A conflict happens when214/// the Filter/FilterChooser combo does not know how to distinguish among the215/// Opcodes assigned.216///217/// An example of a conflict is218///219/// Decoding Conflict:220/// ................................221/// 1111............................222/// 1111010.........................223/// 1111010...00....................224/// 1111010...00........0001........225/// 111101000.00........0001........226/// 111101000.00........00010000....227/// 111101000_00________00010000____ VST4q8a228/// 111101000_00________00010000____ VST4q8b229///230/// The Debug output shows the path that the decoding tree follows to reach the231/// the conclusion that there is a conflict. VST4q8a is a vst4 to double-spaced232/// even registers, while VST4q8b is a vst4 to double-spaced odd registers.233///234/// The encoding info in the .td files does not specify this meta information,235/// which could have been used by the decoder to resolve the conflict. The236/// decoder could try to decode the even/odd register numbering and assign to237/// VST4q8a or VST4q8b, but for the time being, the decoder chooses the "a"238/// version and return the Opcode since the two have the same Asm format string.239struct Filter {240 unsigned StartBit; // the starting bit position241 unsigned NumBits; // number of bits to filter242 243 // Map of well-known segment value to the set of uid's with that value.244 std::map<uint64_t, std::vector<unsigned>> FilteredIDs;245 246 // Set of uid's with non-constant segment values.247 std::vector<unsigned> VariableIDs;248 249 Filter(ArrayRef<InstructionEncoding> Encodings,250 ArrayRef<unsigned> EncodingIDs, unsigned StartBit, unsigned NumBits);251 252 // Returns the number of fanout produced by the filter. More fanout implies253 // the filter distinguishes more categories of instructions.254 unsigned usefulness() const;255}; // end class Filter256 257// These are states of our finite state machines used in FilterChooser's258// filterProcessor() which produces the filter candidates to use.259enum bitAttr_t {260 ATTR_NONE,261 ATTR_FILTERED,262 ATTR_ALL_SET,263 ATTR_ALL_UNSET,264 ATTR_MIXED265};266 267/// FilterChooser - FilterChooser chooses the best filter among a set of Filters268/// in order to perform the decoding of instructions at the current level.269///270/// Decoding proceeds from the top down. Based on the well-known encoding bits271/// of instructions available, FilterChooser builds up the possible Filters that272/// can further the task of decoding by distinguishing among the remaining273/// candidate instructions.274///275/// Once a filter has been chosen, it is called upon to divide the decoding task276/// into sub-tasks and delegates them to its inferior FilterChoosers for further277/// processings.278///279/// It is useful to think of a Filter as governing the switch stmts of the280/// decoding tree. And each case is delegated to an inferior FilterChooser to281/// decide what further remaining bits to look at.282 283class FilterChooser {284 // TODO: Unfriend by providing the necessary accessors.285 friend class DecoderTreeBuilder;286 287 // Vector of encodings to choose our filter.288 ArrayRef<InstructionEncoding> Encodings;289 290 /// Encoding IDs for this filter chooser to work on.291 /// Sorted by non-decreasing encoding width.292 SmallVector<unsigned, 0> EncodingIDs;293 294 // Array of bit values passed down from our parent.295 // Set to all unknown for Parent == nullptr.296 KnownBits FilterBits;297 298 // Links to the FilterChooser above us in the decoding tree.299 const FilterChooser *Parent;300 301 /// If the selected filter matches multiple encodings, then this is the302 /// starting position and the width of the filtered range.303 unsigned StartBit;304 unsigned NumBits;305 306 /// If the selected filter matches multiple encodings, and there is307 /// *exactly one* encoding in which all bits are known in the filtered range,308 /// then this is the ID of that encoding.309 /// Also used when there is only one encoding.310 std::optional<unsigned> SingletonEncodingID;311 312 /// If the selected filter matches multiple encodings, and there is313 /// *at least one* encoding in which all bits are known in the filtered range,314 /// then this is the FilterChooser created for the subset of encodings that315 /// contain some unknown bits in the filtered range.316 std::unique_ptr<const FilterChooser> VariableFC;317 318 /// If the selected filter matches multiple encodings, and there is319 /// *more than one* encoding in which all bits are known in the filtered320 /// range, then this is a map of field values to FilterChoosers created for321 /// the subset of encodings sharing that field value.322 /// The "field value" here refers to the encoding bits in the filtered range.323 std::map<uint64_t, std::unique_ptr<const FilterChooser>> FilterChooserMap;324 325 /// Set to true if decoding conflict was encountered.326 bool HasConflict = false;327 328public:329 /// Constructs a top-level filter chooser.330 FilterChooser(ArrayRef<InstructionEncoding> Encodings,331 ArrayRef<unsigned> EncodingIDs)332 : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(nullptr) {333 // Sort encoding IDs once.334 stable_sort(this->EncodingIDs, LessEncodingIDByWidth(Encodings));335 // Filter width is the width of the smallest encoding.336 unsigned FilterWidth = Encodings[this->EncodingIDs.front()].getBitWidth();337 FilterBits = KnownBits(FilterWidth);338 doFilter();339 }340 341 /// Constructs an inferior filter chooser.342 FilterChooser(ArrayRef<InstructionEncoding> Encodings,343 ArrayRef<unsigned> EncodingIDs, const KnownBits &FilterBits,344 const FilterChooser &Parent)345 : Encodings(Encodings), EncodingIDs(EncodingIDs), Parent(&Parent) {346 // Inferior filter choosers are created from sorted array of encoding IDs.347 assert(is_sorted(EncodingIDs, LessEncodingIDByWidth(Encodings)));348 assert(!FilterBits.hasConflict() && "Broken filter");349 // Filter width is the width of the smallest encoding.350 unsigned FilterWidth = Encodings[EncodingIDs.front()].getBitWidth();351 this->FilterBits = FilterBits.anyext(FilterWidth);352 doFilter();353 }354 355 FilterChooser(const FilterChooser &) = delete;356 void operator=(const FilterChooser &) = delete;357 358 /// Returns the width of the largest encoding.359 unsigned getMaxEncodingWidth() const {360 // The last encoding ID is the ID of an encoding with the largest width.361 return Encodings[EncodingIDs.back()].getBitWidth();362 }363 364 /// Returns true if any decoding conflicts were encountered.365 bool hasConflict() const { return HasConflict; }366 367private:368 /// Applies the given filter to the set of encodings this FilterChooser369 /// works with, creating inferior FilterChoosers as necessary.370 void applyFilter(const Filter &F);371 372 /// dumpStack - dumpStack traverses the filter chooser chain and calls373 /// dumpFilterArray on each filter chooser up to the top level one.374 void dumpStack(raw_ostream &OS, indent Indent, unsigned PadToWidth) const;375 376 bool isPositionFiltered(unsigned Idx) const {377 return FilterBits.Zero[Idx] || FilterBits.One[Idx];378 }379 380 /// Scans the well-known encoding bits of the encodings and, builds up a list381 /// of candidate filters, and then returns the best one, if any.382 std::unique_ptr<Filter> findBestFilter(ArrayRef<bitAttr_t> BitAttrs,383 bool AllowMixed,384 bool Greedy = true) const;385 386 std::unique_ptr<Filter> findBestFilter() const;387 388 // Decides on the best configuration of filter(s) to use in order to decode389 // the instructions. A conflict of instructions may occur, in which case we390 // dump the conflict set to the standard error.391 void doFilter();392 393public:394 void dump() const;395};396 397} // end anonymous namespace398 399///////////////////////////400// //401// Filter Implementation //402// //403///////////////////////////404 405Filter::Filter(ArrayRef<InstructionEncoding> Encodings,406 ArrayRef<unsigned> EncodingIDs, unsigned StartBit,407 unsigned NumBits)408 : StartBit(StartBit), NumBits(NumBits) {409 for (unsigned EncodingID : EncodingIDs) {410 const InstructionEncoding &Encoding = Encodings[EncodingID];411 KnownBits EncodingBits = Encoding.getMandatoryBits();412 413 // Scans the segment for possibly well-specified encoding bits.414 KnownBits FieldBits = EncodingBits.extractBits(NumBits, StartBit);415 416 if (FieldBits.isConstant()) {417 // The encoding bits are well-known. Lets add the uid of the418 // instruction into the bucket keyed off the constant field value.419 FilteredIDs[FieldBits.getConstant().getZExtValue()].push_back(EncodingID);420 } else {421 // Some of the encoding bit(s) are unspecified. This contributes to422 // one additional member of "Variable" instructions.423 VariableIDs.push_back(EncodingID);424 }425 }426 427 assert((FilteredIDs.size() + VariableIDs.size() > 0) &&428 "Filter returns no instruction categories");429}430 431void FilterChooser::applyFilter(const Filter &F) {432 StartBit = F.StartBit;433 NumBits = F.NumBits;434 assert(FilterBits.extractBits(NumBits, StartBit).isUnknown());435 436 if (!F.VariableIDs.empty()) {437 // Delegates to an inferior filter chooser for further processing on this438 // group of instructions whose segment values are variable.439 VariableFC = std::make_unique<FilterChooser>(Encodings, F.VariableIDs,440 FilterBits, *this);441 HasConflict |= VariableFC->HasConflict;442 }443 444 // Otherwise, create sub choosers.445 for (const auto &[FilterVal, InferiorEncodingIDs] : F.FilteredIDs) {446 // Create a new filter by inserting the field bits into the parent filter.447 APInt FieldBits(NumBits, FilterVal);448 KnownBits InferiorFilterBits = FilterBits;449 InferiorFilterBits.insertBits(KnownBits::makeConstant(FieldBits), StartBit);450 451 // Delegates to an inferior filter chooser for further processing on this452 // category of instructions.453 auto [It, _] = FilterChooserMap.try_emplace(454 FilterVal,455 std::make_unique<FilterChooser>(Encodings, InferiorEncodingIDs,456 InferiorFilterBits, *this));457 HasConflict |= It->second->HasConflict;458 }459}460 461// Returns the number of fanout produced by the filter. More fanout implies462// the filter distinguishes more categories of instructions.463unsigned Filter::usefulness() const {464 return FilteredIDs.size() + VariableIDs.empty();465}466 467//////////////////////////////////468// //469// Filterchooser Implementation //470// //471//////////////////////////////////472 473void DecoderEmitter::emitInstrLenTable(formatted_raw_ostream &OS,474 ArrayRef<unsigned> InstrLen) const {475 OS << "static const uint8_t InstrLenTable[] = {\n";476 for (unsigned Len : InstrLen)477 OS << Len << ",\n";478 OS << "};\n\n";479}480 481void DecoderEmitter::emitPredicateFunction(482 formatted_raw_ostream &OS, const PredicateSet &Predicates) const {483 // The predicate function is just a big switch statement based on the484 // input predicate index.485 OS << "static bool checkDecoderPredicate(unsigned Idx, const FeatureBitset "486 "&FB) {\n";487 OS << " switch (Idx) {\n";488 OS << " default: llvm_unreachable(\"Invalid index!\");\n";489 for (const auto &[Index, Predicate] : enumerate(Predicates)) {490 OS << " case " << Index << ":\n";491 OS << " return " << Predicate << ";\n";492 }493 OS << " }\n";494 OS << "}\n\n";495}496 497/// Emit a default implementation of a decoder for all RegClassByHwModes which498/// do not have an explicit DecoderMethodSet, which dispatches over the decoder499/// methods for the member classes.500void DecoderEmitter::emitRegClassByHwModeDecoders(501 formatted_raw_ostream &OS) const {502 const CodeGenHwModes &CGH = Target.getHwModes();503 if (CGH.getNumModeIds() == 1)504 return;505 506 ArrayRef<const Record *> RegClassByHwMode = Target.getAllRegClassByHwMode();507 if (RegClassByHwMode.empty())508 return;509 510 for (const Record *ClassByHwMode : RegClassByHwMode) {511 // Ignore cases that had an explicit DecoderMethod set.512 if (!InstructionEncoding::findOperandDecoderMethod(ClassByHwMode).second)513 continue;514 515 const HwModeSelect &ModeSelect = CGH.getHwModeSelect(ClassByHwMode);516 517 // Mips has a system where this is only used by compound operands with518 // custom decoders, and we don't try to detect if this decoder is really519 // needed.520 OS << "[[maybe_unused]]\n";521 522 OS << "static DecodeStatus Decode" << ClassByHwMode->getName()523 << "RegClassByHwMode";524 OS << R"((MCInst &Inst, unsigned Imm, uint64_t Addr, const MCDisassembler *Decoder) {525 switch (Decoder->getSubtargetInfo().getHwMode(MCSubtargetInfo::HwMode_RegInfo)) {526)";527 for (auto [ModeID, RegClassRec] : ModeSelect.Items) {528 OS << indent(2) << "case " << ModeID << ": // "529 << CGH.getModeName(ModeID, /*IncludeDefault=*/true) << '\n'530 << indent(4) << "return "531 << InstructionEncoding::findOperandDecoderMethod(RegClassRec).first532 << "(Inst, Imm, Addr, Decoder);\n";533 }534 OS << indent(2) << R"(default:535 llvm_unreachable("no decoder for hwmode");536 }537}538 539)";540 }541 542 OS << '\n';543}544 545void DecoderEmitter::emitDecoderFunction(formatted_raw_ostream &OS,546 const DecoderSet &Decoders,547 unsigned BucketBitWidth) const {548 // The decoder function is just a big switch statement or a table of function549 // pointers based on the input decoder index.550 551 // TODO: When InsnType is large, using uint64_t limits all fields to 64 bits552 // It would be better for emitBinaryParser to use a 64-bit tmp whenever553 // possible but fall back to an InsnType-sized tmp for truly large fields.554 StringRef TmpTypeDecl =555 "using TmpType = std::conditional_t<std::is_integral<InsnType>::value, "556 "InsnType, uint64_t>;\n";557 StringRef DecodeParams =558 "DecodeStatus S, InsnType insn, MCInst &MI, uint64_t Address, const "559 "MCDisassembler *Decoder, bool &DecodeComplete";560 561 // Print the name of the decode function to OS.562 auto PrintDecodeFnName = [&OS, BucketBitWidth](unsigned DecodeIdx) {563 OS << "decodeFn";564 if (BucketBitWidth != 0) {565 OS << '_' << BucketBitWidth << "bit";566 }567 OS << '_' << DecodeIdx;568 };569 570 // Print the template statement.571 auto PrintTemplate = [&OS, BucketBitWidth]() {572 OS << "template <typename InsnType>\n";573 OS << "static ";574 if (BucketBitWidth != 0)575 OS << "std::enable_if_t<InsnBitWidth<InsnType> == " << BucketBitWidth576 << ", DecodeStatus>\n";577 else578 OS << "DecodeStatus ";579 };580 581 if (UseFnTableInDecodeToMCInst) {582 // Emit a function for each case first.583 for (const auto &[Index, Decoder] : enumerate(Decoders)) {584 PrintTemplate();585 PrintDecodeFnName(Index);586 OS << "(" << DecodeParams << ") {\n";587 OS << " " << TmpTypeDecl;588 OS << " [[maybe_unused]] TmpType tmp;\n";589 OS << Decoder;590 OS << " return S;\n";591 OS << "}\n\n";592 }593 }594 595 OS << "// Handling " << Decoders.size() << " cases.\n";596 PrintTemplate();597 OS << "decodeToMCInst(unsigned Idx, " << DecodeParams << ") {\n";598 OS << " DecodeComplete = true;\n";599 600 if (UseFnTableInDecodeToMCInst) {601 // Build a table of function pointers602 OS << " using DecodeFnTy = DecodeStatus (*)(" << DecodeParams << ");\n";603 OS << " static constexpr DecodeFnTy decodeFnTable[] = {\n";604 for (size_t Index : llvm::seq(Decoders.size())) {605 OS << " ";606 PrintDecodeFnName(Index);607 OS << ",\n";608 }609 OS << " };\n";610 OS << " if (Idx >= " << Decoders.size() << ")\n";611 OS << " llvm_unreachable(\"Invalid decoder index!\");\n";612 OS << " return decodeFnTable[Idx](S, insn, MI, Address, Decoder, "613 "DecodeComplete);\n";614 } else {615 OS << " " << TmpTypeDecl;616 OS << " TmpType tmp;\n";617 OS << " switch (Idx) {\n";618 OS << " default: llvm_unreachable(\"Invalid decoder index!\");\n";619 for (const auto &[Index, Decoder] : enumerate(Decoders)) {620 OS << " case " << Index << ":\n";621 OS << Decoder;622 OS << " return S;\n";623 }624 OS << " }\n";625 }626 OS << "}\n";627}628 629/// dumpStack - dumpStack traverses the filter chooser chain and calls630/// dumpFilterArray on each filter chooser up to the top level one.631void FilterChooser::dumpStack(raw_ostream &OS, indent Indent,632 unsigned PadToWidth) const {633 if (Parent)634 Parent->dumpStack(OS, Indent, PadToWidth);635 assert(PadToWidth >= FilterBits.getBitWidth());636 OS << Indent << indent(PadToWidth - FilterBits.getBitWidth());637 printKnownBits(OS, FilterBits, '.');638 OS << '\n';639}640 641// Calculates the island(s) needed to decode the instruction.642// This returns a list of undecoded bits of an instructions, for example,643// Inst{20} = 1 && Inst{3-0} == 0b1111 represents two islands of yet-to-be644// decoded bits in order to verify that the instruction matches the Opcode.645static std::vector<EncodingIsland> getIslands(const KnownBits &EncodingBits,646 const KnownBits &FilterBits) {647 std::vector<EncodingIsland> Islands;648 uint64_t FieldVal;649 unsigned StartBit;650 651 bool OnIsland = false;652 unsigned FilterWidth = FilterBits.getBitWidth();653 for (unsigned I = 0; I != FilterWidth; ++I) {654 bool IsKnown = EncodingBits.Zero[I] || EncodingBits.One[I];655 bool IsFiltered = FilterBits.Zero[I] || FilterBits.One[I];656 if (!IsFiltered && IsKnown) {657 if (OnIsland) {658 // Accumulate island bits.659 FieldVal |= static_cast<uint64_t>(EncodingBits.One[I])660 << (I - StartBit);661 } else {662 // Onto an island.663 StartBit = I;664 FieldVal = static_cast<uint64_t>(EncodingBits.One[I]);665 OnIsland = true;666 }667 } else if (OnIsland) {668 // Into the water.669 Islands.push_back({StartBit, I - StartBit, FieldVal});670 OnIsland = false;671 }672 }673 674 if (OnIsland)675 Islands.push_back({StartBit, FilterWidth - StartBit, FieldVal});676 677 return Islands;678}679 680static void emitBinaryParser(raw_ostream &OS, indent Indent,681 const InstructionEncoding &Encoding,682 const OperandInfo &OpInfo) {683 if (OpInfo.HasNoEncoding) {684 // If an operand has no encoding, the old behavior is to not decode it685 // automatically and let the target do it. This is error-prone, so the686 // new behavior is to report an error.687 if (!IgnoreNonDecodableOperands)688 PrintError(Encoding.getRecord()->getLoc(),689 "could not find field for operand '" + OpInfo.Name + "'");690 return;691 }692 693 // Special case for 'bits<0>'.694 if (OpInfo.Fields.empty() && !OpInfo.InitValue) {695 assert(!OpInfo.Decoder.empty());696 // The operand has no encoding, so the corresponding argument is omitted.697 // This avoids confusion and allows the function to be overloaded if the698 // operand does have an encoding in other instructions.699 OS << Indent << "if (!Check(S, " << OpInfo.Decoder << "(MI, Decoder)))\n"700 << Indent << " return MCDisassembler::Fail;\n";701 return;702 }703 704 if (OpInfo.fields().empty()) {705 // Only a constant part. The old behavior is to not decode this operand.706 if (IgnoreFullyDefinedOperands)707 return;708 // Initialize `tmp` with the constant part.709 OS << Indent << "tmp = " << format_hex(*OpInfo.InitValue, 0) << ";\n";710 } else if (OpInfo.fields().size() == 1 && !OpInfo.InitValue.value_or(0)) {711 // One variable part and no/zero constant part. Initialize `tmp` with the712 // variable part.713 auto [Base, Width, Offset] = OpInfo.fields().front();714 OS << Indent << "tmp = fieldFromInstruction(insn, " << Base << ", " << Width715 << ')';716 if (Offset)717 OS << " << " << Offset;718 OS << ";\n";719 } else {720 // General case. Initialize `tmp` with the constant part, if any, and721 // insert the variable parts into it.722 OS << Indent << "tmp = " << format_hex(OpInfo.InitValue.value_or(0), 0)723 << ";\n";724 for (auto [Base, Width, Offset] : OpInfo.fields()) {725 OS << Indent << "tmp |= fieldFromInstruction(insn, " << Base << ", "726 << Width << ')';727 if (Offset)728 OS << " << " << Offset;729 OS << ";\n";730 }731 }732 733 StringRef Decoder = OpInfo.Decoder;734 if (!Decoder.empty()) {735 OS << Indent << "if (!Check(S, " << Decoder736 << "(MI, tmp, Address, Decoder))) { "737 << (OpInfo.HasCompleteDecoder ? "" : "DecodeComplete = false; ")738 << "return MCDisassembler::Fail; }\n";739 } else {740 OS << Indent << "MI.addOperand(MCOperand::createImm(tmp));\n";741 }742}743 744static std::string getDecoderString(const InstructionEncoding &Encoding) {745 std::string Decoder;746 raw_string_ostream OS(Decoder);747 indent Indent(UseFnTableInDecodeToMCInst ? 2 : 4);748 749 // If a custom instruction decoder was specified, use that.750 StringRef DecoderMethod = Encoding.getDecoderMethod();751 if (!DecoderMethod.empty()) {752 OS << Indent << "if (!Check(S, " << DecoderMethod753 << "(MI, insn, Address, Decoder))) { "754 << (Encoding.hasCompleteDecoder() ? "" : "DecodeComplete = false; ")755 << "return MCDisassembler::Fail; }\n";756 } else {757 for (const OperandInfo &Op : Encoding.getOperands())758 emitBinaryParser(OS, Indent, Encoding, Op);759 }760 return Decoder;761}762 763static std::string getPredicateString(const InstructionEncoding &Encoding,764 StringRef TargetName) {765 std::vector<const Record *> Predicates =766 Encoding.getRecord()->getValueAsListOfDefs("Predicates");767 auto It = llvm::find_if(Predicates, [](const Record *R) {768 return R->getValueAsBit("AssemblerMatcherPredicate");769 });770 if (It == Predicates.end())771 return std::string();772 773 std::string Predicate;774 raw_string_ostream OS(Predicate);775 SubtargetFeatureInfo::emitMCPredicateCheck(OS, TargetName, Predicates);776 return Predicate;777}778 779std::unique_ptr<Filter>780FilterChooser::findBestFilter(ArrayRef<bitAttr_t> BitAttrs, bool AllowMixed,781 bool Greedy) const {782 assert(EncodingIDs.size() >= 2 && "Nothing to filter");783 784 // Heuristics. See also doFilter()'s "Heuristics" comment when num of785 // instructions is 3.786 if (AllowMixed && !Greedy) {787 assert(EncodingIDs.size() == 3);788 789 for (unsigned EncodingID : EncodingIDs) {790 const InstructionEncoding &Encoding = Encodings[EncodingID];791 KnownBits EncodingBits = Encoding.getMandatoryBits();792 793 // Look for islands of undecoded bits of any instruction.794 std::vector<EncodingIsland> Islands =795 getIslands(EncodingBits, FilterBits);796 if (!Islands.empty()) {797 // Found an instruction with island(s). Now just assign a filter.798 return std::make_unique<Filter>(799 Encodings, EncodingIDs, Islands[0].StartBit, Islands[0].NumBits);800 }801 }802 }803 804 // The regionAttr automaton consumes the bitAttrs automatons' state,805 // lowest-to-highest.806 //807 // Input symbols: F(iltered), (all_)S(et), (all_)U(nset), M(ixed)808 // States: NONE, ALL_SET, MIXED809 // Initial state: NONE810 //811 // (NONE) ----- F --> (NONE)812 // (NONE) ----- S --> (ALL_SET) ; and set region start813 // (NONE) ----- U --> (NONE)814 // (NONE) ----- M --> (MIXED) ; and set region start815 // (ALL_SET) -- F --> (NONE) ; and report an ALL_SET region816 // (ALL_SET) -- S --> (ALL_SET)817 // (ALL_SET) -- U --> (NONE) ; and report an ALL_SET region818 // (ALL_SET) -- M --> (MIXED) ; and report an ALL_SET region819 // (MIXED) ---- F --> (NONE) ; and report a MIXED region820 // (MIXED) ---- S --> (ALL_SET) ; and report a MIXED region821 // (MIXED) ---- U --> (NONE) ; and report a MIXED region822 // (MIXED) ---- M --> (MIXED)823 824 bitAttr_t RA = ATTR_NONE;825 unsigned StartBit = 0;826 827 std::vector<std::unique_ptr<Filter>> Filters;828 829 auto addCandidateFilter = [&](unsigned StartBit, unsigned EndBit) {830 Filters.push_back(std::make_unique<Filter>(Encodings, EncodingIDs, StartBit,831 EndBit - StartBit));832 };833 834 unsigned FilterWidth = FilterBits.getBitWidth();835 for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++BitIndex) {836 bitAttr_t bitAttr = BitAttrs[BitIndex];837 838 assert(bitAttr != ATTR_NONE && "Bit without attributes");839 840 switch (RA) {841 case ATTR_NONE:842 switch (bitAttr) {843 case ATTR_FILTERED:844 break;845 case ATTR_ALL_SET:846 StartBit = BitIndex;847 RA = ATTR_ALL_SET;848 break;849 case ATTR_ALL_UNSET:850 break;851 case ATTR_MIXED:852 StartBit = BitIndex;853 RA = ATTR_MIXED;854 break;855 default:856 llvm_unreachable("Unexpected bitAttr!");857 }858 break;859 case ATTR_ALL_SET:860 if (!AllowMixed && bitAttr != ATTR_ALL_SET)861 addCandidateFilter(StartBit, BitIndex);862 switch (bitAttr) {863 case ATTR_FILTERED:864 RA = ATTR_NONE;865 break;866 case ATTR_ALL_SET:867 break;868 case ATTR_ALL_UNSET:869 RA = ATTR_NONE;870 break;871 case ATTR_MIXED:872 StartBit = BitIndex;873 RA = ATTR_MIXED;874 break;875 default:876 llvm_unreachable("Unexpected bitAttr!");877 }878 break;879 case ATTR_MIXED:880 if (AllowMixed && bitAttr != ATTR_MIXED)881 addCandidateFilter(StartBit, BitIndex);882 switch (bitAttr) {883 case ATTR_FILTERED:884 StartBit = BitIndex;885 RA = ATTR_NONE;886 break;887 case ATTR_ALL_SET:888 StartBit = BitIndex;889 RA = ATTR_ALL_SET;890 break;891 case ATTR_ALL_UNSET:892 RA = ATTR_NONE;893 break;894 case ATTR_MIXED:895 break;896 default:897 llvm_unreachable("Unexpected bitAttr!");898 }899 break;900 case ATTR_ALL_UNSET:901 llvm_unreachable("regionAttr state machine has no ATTR_UNSET state");902 case ATTR_FILTERED:903 llvm_unreachable("regionAttr state machine has no ATTR_FILTERED state");904 }905 }906 907 // At the end, if we're still in ALL_SET or MIXED states, report a region908 switch (RA) {909 case ATTR_NONE:910 break;911 case ATTR_FILTERED:912 break;913 case ATTR_ALL_SET:914 if (!AllowMixed)915 addCandidateFilter(StartBit, FilterWidth);916 break;917 case ATTR_ALL_UNSET:918 break;919 case ATTR_MIXED:920 if (AllowMixed)921 addCandidateFilter(StartBit, FilterWidth);922 break;923 }924 925 // We have finished with the filter processings. Now it's time to choose926 // the best performing filter.927 auto MaxIt = llvm::max_element(Filters, [](const std::unique_ptr<Filter> &A,928 const std::unique_ptr<Filter> &B) {929 return A->usefulness() < B->usefulness();930 });931 if (MaxIt == Filters.end() || (*MaxIt)->usefulness() == 0)932 return nullptr;933 return std::move(*MaxIt);934}935 936std::unique_ptr<Filter> FilterChooser::findBestFilter() const {937 // We maintain BIT_WIDTH copies of the bitAttrs automaton.938 // The automaton consumes the corresponding bit from each939 // instruction.940 //941 // Input symbols: 0, 1, _ (unset), and . (any of the above).942 // States: NONE, FILTERED, ALL_SET, ALL_UNSET, and MIXED.943 // Initial state: NONE.944 //945 // (NONE) ------- [01] -> (ALL_SET)946 // (NONE) ------- _ ----> (ALL_UNSET)947 // (ALL_SET) ---- [01] -> (ALL_SET)948 // (ALL_SET) ---- _ ----> (MIXED)949 // (ALL_UNSET) -- [01] -> (MIXED)950 // (ALL_UNSET) -- _ ----> (ALL_UNSET)951 // (MIXED) ------ . ----> (MIXED)952 // (FILTERED)---- . ----> (FILTERED)953 954 unsigned FilterWidth = FilterBits.getBitWidth();955 SmallVector<bitAttr_t, 128> BitAttrs(FilterWidth, ATTR_NONE);956 957 // FILTERED bit positions provide no entropy and are not worthy of pursuing.958 // Filter::recurse() set either 1 or 0 for each position.959 for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++BitIndex)960 if (isPositionFiltered(BitIndex))961 BitAttrs[BitIndex] = ATTR_FILTERED;962 963 for (unsigned EncodingID : EncodingIDs) {964 const InstructionEncoding &Encoding = Encodings[EncodingID];965 KnownBits EncodingBits = Encoding.getMandatoryBits();966 967 for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++BitIndex) {968 bool IsKnown = EncodingBits.Zero[BitIndex] || EncodingBits.One[BitIndex];969 switch (BitAttrs[BitIndex]) {970 case ATTR_NONE:971 if (IsKnown)972 BitAttrs[BitIndex] = ATTR_ALL_SET;973 else974 BitAttrs[BitIndex] = ATTR_ALL_UNSET;975 break;976 case ATTR_ALL_SET:977 if (!IsKnown)978 BitAttrs[BitIndex] = ATTR_MIXED;979 break;980 case ATTR_ALL_UNSET:981 if (IsKnown)982 BitAttrs[BitIndex] = ATTR_MIXED;983 break;984 case ATTR_MIXED:985 case ATTR_FILTERED:986 break;987 }988 }989 }990 991 // Try regions of consecutive known bit values first.992 if (std::unique_ptr<Filter> F =993 findBestFilter(BitAttrs, /*AllowMixed=*/false))994 return F;995 996 // Then regions of mixed bits (both known and unitialized bit values allowed).997 if (std::unique_ptr<Filter> F = findBestFilter(BitAttrs, /*AllowMixed=*/true))998 return F;999 1000 // Heuristics to cope with conflict set {t2CMPrs, t2SUBSrr, t2SUBSrs} where1001 // no single instruction for the maximum ATTR_MIXED region Inst{14-4} has a1002 // well-known encoding pattern. In such case, we backtrack and scan for the1003 // the very first consecutive ATTR_ALL_SET region and assign a filter to it.1004 if (EncodingIDs.size() == 3) {1005 if (std::unique_ptr<Filter> F =1006 findBestFilter(BitAttrs, /*AllowMixed=*/true, /*Greedy=*/false))1007 return F;1008 }1009 1010 // There is a conflict we could not resolve.1011 return nullptr;1012}1013 1014// Decides on the best configuration of filter(s) to use in order to decode1015// the instructions. A conflict of instructions may occur, in which case we1016// dump the conflict set to the standard error.1017void FilterChooser::doFilter() {1018 assert(!EncodingIDs.empty() && "FilterChooser created with no instructions");1019 1020 // No filter needed.1021 if (EncodingIDs.size() == 1) {1022 SingletonEncodingID = EncodingIDs.front();1023 return;1024 }1025 1026 std::unique_ptr<Filter> BestFilter = findBestFilter();1027 if (BestFilter) {1028 applyFilter(*BestFilter);1029 return;1030 }1031 1032 // Print out useful conflict information for postmortem analysis.1033 errs() << "Decoding Conflict:\n";1034 dump();1035 HasConflict = true;1036}1037 1038void FilterChooser::dump() const {1039 indent Indent(4);1040 // Helps to keep the output right-justified.1041 unsigned PadToWidth = getMaxEncodingWidth();1042 1043 // Dump filter stack.1044 dumpStack(errs(), Indent, PadToWidth);1045 1046 // Dump encodings.1047 for (unsigned EncodingID : EncodingIDs) {1048 const InstructionEncoding &Encoding = Encodings[EncodingID];1049 errs() << Indent << indent(PadToWidth - Encoding.getBitWidth());1050 printKnownBits(errs(), Encoding.getMandatoryBits(), '_');1051 errs() << " " << Encoding.getName() << '\n';1052 }1053}1054 1055// emitDecodeInstruction - Emit the templated helper function1056// decodeInstruction().1057static void emitDecodeInstruction(formatted_raw_ostream &OS, bool IsVarLenInst,1058 const DecoderTableInfo &TableInfo) {1059 OS << R"(1060template <typename InsnType>1061static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], MCInst &MI,1062 InsnType insn, uint64_t Address,1063 const MCDisassembler *DisAsm,1064 const MCSubtargetInfo &STI)";1065 if (IsVarLenInst) {1066 OS << ",\n "1067 "llvm::function_ref<void(APInt &, uint64_t)> makeUp";1068 }1069 OS << ") {\n";1070 if (TableInfo.HasCheckPredicate)1071 OS << " const FeatureBitset &Bits = STI.getFeatureBits();\n";1072 OS << " const uint8_t *Ptr = DecodeTable;\n";1073 1074 if (SpecializeDecodersPerBitwidth) {1075 // Fail with a fatal error if decoder table's bitwidth does not match1076 // `InsnType` bitwidth.1077 OS << R"(1078 [[maybe_unused]] uint32_t BitWidth = decodeULEB128AndIncUnsafe(Ptr);1079 assert(InsnBitWidth<InsnType> == BitWidth &&1080 "Table and instruction bitwidth mismatch");1081)";1082 }1083 1084 OS << R"(1085 SmallVector<const uint8_t *, 8> ScopeStack;1086 DecodeStatus S = MCDisassembler::Success;1087 while (true) {1088 ptrdiff_t Loc = Ptr - DecodeTable;1089 const uint8_t DecoderOp = *Ptr++;1090 switch (DecoderOp) {1091 default:1092 errs() << Loc << ": Unexpected decode table opcode: "1093 << (int)DecoderOp << '\n';1094 return MCDisassembler::Fail;1095 case OPC_Scope: {1096 unsigned NumToSkip = decodeULEB128AndIncUnsafe(Ptr);1097 const uint8_t *SkipTo = Ptr + NumToSkip;1098 ScopeStack.push_back(SkipTo);1099 LLVM_DEBUG(dbgs() << Loc << ": OPC_Scope(" << SkipTo - DecodeTable1100 << ")\n");1101 continue;1102 }1103 case OPC_SwitchField: {1104 // Decode the start value.1105 unsigned Start = decodeULEB128AndIncUnsafe(Ptr);1106 unsigned Len = *Ptr++;)";1107 if (IsVarLenInst)1108 OS << "\n makeUp(insn, Start + Len);";1109 OS << R"(1110 uint64_t FieldValue = fieldFromInstruction(insn, Start, Len);1111 uint64_t CaseValue;1112 unsigned CaseSize;1113 while (true) {1114 CaseValue = decodeULEB128AndIncUnsafe(Ptr);1115 CaseSize = decodeULEB128AndIncUnsafe(Ptr);1116 if (FieldValue == CaseValue || !CaseSize)1117 break;1118 Ptr += CaseSize;1119 }1120 if (FieldValue == CaseValue) {1121 LLVM_DEBUG(dbgs() << Loc << ": OPC_SwitchField(" << Start << ", " << Len1122 << "): " << FieldValue << '\n');1123 continue;1124 }1125 break;1126 }1127 case OPC_CheckField: {1128 // Decode the start value.1129 unsigned Start = decodeULEB128AndIncUnsafe(Ptr);1130 unsigned Len = *Ptr;)";1131 if (IsVarLenInst)1132 OS << "\n makeUp(insn, Start + Len);";1133 OS << R"(1134 uint64_t FieldValue = fieldFromInstruction(insn, Start, Len);1135 // Decode the field value.1136 unsigned PtrLen = 0;1137 uint64_t ExpectedValue = decodeULEB128(++Ptr, &PtrLen);1138 Ptr += PtrLen;1139 bool Failed = ExpectedValue != FieldValue;1140 1141 LLVM_DEBUG(dbgs() << Loc << ": OPC_CheckField(" << Start << ", " << Len1142 << ", " << ExpectedValue << "): FieldValue = "1143 << FieldValue << ", ExpectedValue = " << ExpectedValue1144 << ": " << (Failed ? "FAIL, " : "PASS\n"););1145 if (!Failed)1146 continue;1147 break;1148 })";1149 if (TableInfo.HasCheckPredicate) {1150 OS << R"(1151 case OPC_CheckPredicate: {1152 // Decode the Predicate Index value.1153 unsigned PIdx = decodeULEB128AndIncUnsafe(Ptr);1154 // Check the predicate.1155 bool Failed = !checkDecoderPredicate(PIdx, Bits);1156 1157 LLVM_DEBUG(dbgs() << Loc << ": OPC_CheckPredicate(" << PIdx << "): "1158 << (Failed ? "FAIL, " : "PASS\n"););1159 if (!Failed)1160 continue;1161 break;1162 })";1163 }1164 OS << R"(1165 case OPC_Decode: {1166 // Decode the Opcode value.1167 unsigned Opc = decodeULEB128AndIncUnsafe(Ptr);1168 unsigned DecodeIdx = decodeULEB128AndIncUnsafe(Ptr);1169 1170 MI.clear();1171 MI.setOpcode(Opc);1172 bool DecodeComplete;)";1173 if (IsVarLenInst) {1174 OS << "\n unsigned Len = InstrLenTable[Opc];\n"1175 << " makeUp(insn, Len);";1176 }1177 OS << R"(1178 S = decodeToMCInst(DecodeIdx, S, insn, MI, Address, DisAsm,1179 DecodeComplete);1180 LLVM_DEBUG(dbgs() << Loc << ": OPC_Decode: opcode " << Opc1181 << ", using decoder " << DecodeIdx << ": "1182 << (S ? "PASS, " : "FAIL, "));1183 1184 if (DecodeComplete) {1185 LLVM_DEBUG(dbgs() << "decoding complete\n");1186 return S;1187 }1188 assert(S == MCDisassembler::Fail);1189 // Reset decode status. This also drops a SoftFail status that could be1190 // set before the decode attempt.1191 S = MCDisassembler::Success;1192 break;1193 })";1194 if (TableInfo.HasSoftFail) {1195 OS << R"(1196 case OPC_SoftFail: {1197 // Decode the mask values.1198 uint64_t PositiveMask = decodeULEB128AndIncUnsafe(Ptr);1199 uint64_t NegativeMask = decodeULEB128AndIncUnsafe(Ptr);1200 bool Failed = (insn & PositiveMask) != 0 || (~insn & NegativeMask) != 0;1201 if (Failed)1202 S = MCDisassembler::SoftFail;1203 LLVM_DEBUG(dbgs() << Loc << ": OPC_SoftFail: " << (Failed ? "FAIL\n" : "PASS\n"));1204 continue;1205 })";1206 }1207 OS << R"(1208 }1209 if (ScopeStack.empty()) {1210 LLVM_DEBUG(dbgs() << "returning Fail\n");1211 return MCDisassembler::Fail;1212 }1213 Ptr = ScopeStack.pop_back_val();1214 LLVM_DEBUG(dbgs() << "continuing at " << Ptr - DecodeTable << '\n');1215 }1216 llvm_unreachable("bogosity detected in disassembler state machine!");1217}1218 1219)";1220}1221 1222namespace {1223 1224class DecoderTreeBuilder {1225 DecoderContext &Ctx;1226 const CodeGenTarget &Target;1227 ArrayRef<InstructionEncoding> Encodings;1228 1229public:1230 DecoderTreeBuilder(DecoderContext &Ctx, const CodeGenTarget &Target,1231 ArrayRef<InstructionEncoding> Encodings)1232 : Ctx(Ctx), Target(Target), Encodings(Encodings) {}1233 1234 std::unique_ptr<DecoderTreeNode> buildTree(ArrayRef<unsigned> EncodingIDs);1235 1236private:1237 std::unique_ptr<DecoderTreeNode>1238 convertSingleton(unsigned EncodingID, const KnownBits &FilterBits);1239 1240 std::unique_ptr<DecoderTreeNode> convertFilterChooserMap(1241 unsigned StartBit, unsigned NumBits,1242 const std::map<uint64_t, std::unique_ptr<const FilterChooser>> &FCMap);1243 1244 std::unique_ptr<DecoderTreeNode>1245 convertFilterChooser(const FilterChooser *FC);1246};1247 1248} // namespace1249 1250std::unique_ptr<DecoderTreeNode>1251DecoderTreeBuilder::convertSingleton(unsigned EncodingID,1252 const KnownBits &FilterBits) {1253 const InstructionEncoding &Encoding = Encodings[EncodingID];1254 auto N = std::make_unique<CheckAllNode>();1255 1256 std::string Predicate = getPredicateString(Encoding, Target.getName());1257 if (!Predicate.empty()) {1258 unsigned PredicateIndex = Ctx.getPredicateIndex(Predicate);1259 N->addChild(std::make_unique<CheckPredicateNode>(PredicateIndex));1260 }1261 1262 std::vector<EncodingIsland> Islands =1263 getIslands(Encoding.getMandatoryBits(), FilterBits);1264 for (const EncodingIsland &Island : reverse(Islands)) {1265 N->addChild(std::make_unique<CheckFieldNode>(1266 Island.StartBit, Island.NumBits, Island.FieldVal));1267 }1268 1269 const KnownBits &InstBits = Encoding.getInstBits();1270 const APInt &SoftFailMask = Encoding.getSoftFailMask();1271 if (!SoftFailMask.isZero()) {1272 APInt PositiveMask = InstBits.Zero & SoftFailMask;1273 APInt NegativeMask = InstBits.One & SoftFailMask;1274 N->addChild(std::make_unique<SoftFailNode>(PositiveMask.getZExtValue(),1275 NegativeMask.getZExtValue()));1276 }1277 1278 unsigned DecoderIndex = Ctx.getDecoderIndex(getDecoderString(Encoding));1279 N->addChild(std::make_unique<DecodeNode>(1280 Encoding.getName(), Encoding.getInstruction()->EnumVal, DecoderIndex));1281 1282 return N;1283}1284 1285std::unique_ptr<DecoderTreeNode> DecoderTreeBuilder::convertFilterChooserMap(1286 unsigned StartBit, unsigned NumBits,1287 const std::map<uint64_t, std::unique_ptr<const FilterChooser>> &FCMap) {1288 if (FCMap.size() == 1) {1289 const auto &[FieldVal, ChildFC] = *FCMap.begin();1290 auto N = std::make_unique<CheckAllNode>();1291 N->addChild(std::make_unique<CheckFieldNode>(StartBit, NumBits, FieldVal));1292 N->addChild(convertFilterChooser(ChildFC.get()));1293 return N;1294 }1295 auto N = std::make_unique<SwitchFieldNode>(StartBit, NumBits);1296 for (const auto &[FieldVal, ChildFC] : FCMap)1297 N->addCase(FieldVal, convertFilterChooser(ChildFC.get()));1298 return N;1299}1300 1301std::unique_ptr<DecoderTreeNode>1302DecoderTreeBuilder::convertFilterChooser(const FilterChooser *FC) {1303 auto N = std::make_unique<CheckAnyNode>();1304 1305 do {1306 if (FC->SingletonEncodingID)1307 N->addChild(convertSingleton(*FC->SingletonEncodingID, FC->FilterBits));1308 else1309 N->addChild(convertFilterChooserMap(FC->StartBit, FC->NumBits,1310 FC->FilterChooserMap));1311 FC = FC->VariableFC.get();1312 } while (FC);1313 1314 return N;1315}1316 1317std::unique_ptr<DecoderTreeNode>1318DecoderTreeBuilder::buildTree(ArrayRef<unsigned> EncodingIDs) {1319 FilterChooser FC(Encodings, EncodingIDs);1320 if (FC.hasConflict())1321 return nullptr;1322 return convertFilterChooser(&FC);1323}1324 1325/// Collects all HwModes referenced by the target for encoding purposes.1326void DecoderEmitter::collectHwModesReferencedForEncodings(1327 std::vector<unsigned> &HwModeIDs,1328 NamespacesHwModesMap &NamespacesWithHwModes) const {1329 SmallBitVector BV(CGH.getNumModeIds());1330 for (const auto &MS : CGH.getHwModeSelects()) {1331 for (auto [HwModeID, EncodingDef] : MS.second.Items) {1332 if (EncodingDef->isSubClassOf("InstructionEncoding")) {1333 StringRef DecoderNamespace =1334 EncodingDef->getValueAsString("DecoderNamespace");1335 NamespacesWithHwModes[DecoderNamespace].insert(HwModeID);1336 BV.set(HwModeID);1337 }1338 }1339 }1340 // FIXME: Can't do `HwModeIDs.assign(BV.set_bits_begin(), BV.set_bits_end())`1341 // because const_set_bits_iterator_impl is not copy-assignable.1342 // This breaks some MacOS builds.1343 llvm::copy(BV.set_bits(), std::back_inserter(HwModeIDs));1344}1345 1346void DecoderEmitter::handleHwModesUnrelatedEncodings(1347 unsigned EncodingID, ArrayRef<unsigned> HwModeIDs,1348 NamespacesHwModesMap &NamespacesWithHwModes) {1349 switch (DecoderEmitterSuppressDuplicates) {1350 case SUPPRESSION_DISABLE: {1351 for (unsigned HwModeID : HwModeIDs)1352 EncodingIDsByHwMode[HwModeID].push_back(EncodingID);1353 break;1354 }1355 case SUPPRESSION_LEVEL1: {1356 StringRef DecoderNamespace = Encodings[EncodingID].getDecoderNamespace();1357 auto It = NamespacesWithHwModes.find(DecoderNamespace);1358 if (It != NamespacesWithHwModes.end()) {1359 for (unsigned HwModeID : It->second)1360 EncodingIDsByHwMode[HwModeID].push_back(EncodingID);1361 } else {1362 // Only emit the encoding once, as it's DecoderNamespace doesn't1363 // contain any HwModes.1364 EncodingIDsByHwMode[DefaultMode].push_back(EncodingID);1365 }1366 break;1367 }1368 case SUPPRESSION_LEVEL2:1369 EncodingIDsByHwMode[DefaultMode].push_back(EncodingID);1370 break;1371 }1372}1373 1374/// Checks if the given target-specific non-pseudo instruction1375/// is a candidate for decoding.1376static bool isDecodableInstruction(const Record *InstDef) {1377 return !InstDef->getValueAsBit("isAsmParserOnly") &&1378 !InstDef->getValueAsBit("isCodeGenOnly");1379}1380 1381/// Checks if the given encoding is valid.1382static bool isValidEncoding(const Record *EncodingDef) {1383 const RecordVal *InstField = EncodingDef->getValue("Inst");1384 if (!InstField)1385 return false;1386 1387 if (const auto *InstInit = dyn_cast<BitsInit>(InstField->getValue())) {1388 // Fixed-length encoding. Size must be non-zero.1389 if (!EncodingDef->getValueAsInt("Size"))1390 return false;1391 1392 // At least one of the encoding bits must be complete (not '?').1393 // FIXME: This should take SoftFail field into account.1394 return !InstInit->allInComplete();1395 }1396 1397 if (const auto *InstInit = dyn_cast<DagInit>(InstField->getValue())) {1398 // Variable-length encoding.1399 // At least one of the encoding bits must be complete (not '?').1400 VarLenInst VLI(InstInit, InstField);1401 return !all_of(VLI, [](const EncodingSegment &Segment) {1402 return isa<UnsetInit>(Segment.Value);1403 });1404 }1405 1406 // Inst field is neither BitsInit nor DagInit. This is something unsupported.1407 return false;1408}1409 1410/// Parses all InstructionEncoding instances and fills internal data structures.1411void DecoderEmitter::parseInstructionEncodings() {1412 // First, collect all encoding-related HwModes referenced by the target.1413 // And establish a mapping table between DecoderNamespace and HwMode.1414 // If HwModeNames is empty, add the default mode so we always have one HwMode.1415 std::vector<unsigned> HwModeIDs;1416 NamespacesHwModesMap NamespacesWithHwModes;1417 collectHwModesReferencedForEncodings(HwModeIDs, NamespacesWithHwModes);1418 if (HwModeIDs.empty())1419 HwModeIDs.push_back(DefaultMode);1420 1421 ArrayRef<const CodeGenInstruction *> Instructions =1422 Target.getTargetNonPseudoInstructions();1423 Encodings.reserve(Instructions.size());1424 1425 for (const CodeGenInstruction *Inst : Instructions) {1426 const Record *InstDef = Inst->TheDef;1427 if (!isDecodableInstruction(InstDef)) {1428 ++NumEncodingsLackingDisasm;1429 continue;1430 }1431 1432 if (const Record *RV = InstDef->getValueAsOptionalDef("EncodingInfos")) {1433 EncodingInfoByHwMode EBM(RV, CGH);1434 for (auto [HwModeID, EncodingDef] : EBM) {1435 if (!isValidEncoding(EncodingDef)) {1436 // TODO: Should probably give a warning.1437 ++NumEncodingsOmitted;1438 continue;1439 }1440 unsigned EncodingID = Encodings.size();1441 Encodings.emplace_back(EncodingDef, Inst);1442 EncodingIDsByHwMode[HwModeID].push_back(EncodingID);1443 }1444 continue; // Ignore encoding specified by Instruction itself.1445 }1446 1447 if (!isValidEncoding(InstDef)) {1448 ++NumEncodingsOmitted;1449 continue;1450 }1451 1452 unsigned EncodingID = Encodings.size();1453 Encodings.emplace_back(InstDef, Inst);1454 1455 // This instruction is encoded the same on all HwModes.1456 // According to user needs, add it to all, some, or only the default HwMode.1457 handleHwModesUnrelatedEncodings(EncodingID, HwModeIDs,1458 NamespacesWithHwModes);1459 }1460 1461 for (const Record *EncodingDef :1462 RK.getAllDerivedDefinitions("AdditionalEncoding")) {1463 const Record *InstDef = EncodingDef->getValueAsDef("AliasOf");1464 // TODO: Should probably give a warning in these cases.1465 // What's the point of specifying an additional encoding1466 // if it is invalid or if the instruction is not decodable?1467 if (!isDecodableInstruction(InstDef)) {1468 ++NumEncodingsLackingDisasm;1469 continue;1470 }1471 if (!isValidEncoding(EncodingDef)) {1472 ++NumEncodingsOmitted;1473 continue;1474 }1475 unsigned EncodingID = Encodings.size();1476 Encodings.emplace_back(EncodingDef, &Target.getInstruction(InstDef));1477 EncodingIDsByHwMode[DefaultMode].push_back(EncodingID);1478 }1479 1480 // Do some statistics.1481 NumInstructions = Instructions.size();1482 NumEncodingsSupported = Encodings.size();1483 NumEncodings = NumEncodingsSupported + NumEncodingsOmitted;1484}1485 1486DecoderEmitter::DecoderEmitter(const RecordKeeper &RK)1487 : RK(RK), Target(RK), CGH(Target.getHwModes()) {1488 Target.reverseBitsForLittleEndianEncoding();1489 parseInstructionEncodings();1490}1491 1492// Emits disassembler code for instruction decoding.1493void DecoderEmitter::run(raw_ostream &o) const {1494 formatted_raw_ostream OS(o);1495 OS << R"(1496#include "llvm/MC/MCInst.h"1497#include "llvm/MC/MCSubtargetInfo.h"1498#include "llvm/Support/DataTypes.h"1499#include "llvm/Support/Debug.h"1500#include "llvm/Support/LEB128.h"1501#include "llvm/Support/raw_ostream.h"1502#include "llvm/TargetParser/SubtargetFeature.h"1503#include <assert.h>1504 1505namespace {1506 1507// InsnBitWidth is essentially a type trait used by the decoder emitter to query1508// the supported bitwidth for a given type. But default, the value is 0, making1509// it an invalid type for use as `InsnType` when instantiating the decoder.1510// Individual targets are expected to provide specializations for these based1511// on their usage.1512template <typename T> constexpr uint32_t InsnBitWidth = 0;1513 1514)";1515 1516 // Do extra bookkeeping for variable-length encodings.1517 bool IsVarLenInst = Target.hasVariableLengthEncodings();1518 unsigned MaxInstLen = 0;1519 if (IsVarLenInst) {1520 std::vector<unsigned> InstrLen(Target.getInstructions().size(), 0);1521 for (const InstructionEncoding &Encoding : Encodings) {1522 MaxInstLen = std::max(MaxInstLen, Encoding.getBitWidth());1523 InstrLen[Target.getInstrIntValue(Encoding.getInstruction()->TheDef)] =1524 Encoding.getBitWidth();1525 }1526 1527 // For variable instruction, we emit an instruction length table to let the1528 // decoder know how long the instructions are. You can see example usage in1529 // M68k's disassembler.1530 emitInstrLenTable(OS, InstrLen);1531 }1532 1533 emitRegClassByHwModeDecoders(OS);1534 1535 // Map of (bitwidth, namespace, hwmode) tuple to encoding IDs.1536 // Its organized as a nested map, with the (namespace, hwmode) as the key for1537 // the inner map and bitwidth as the key for the outer map. We use std::map1538 // for deterministic iteration order so that the code emitted is also1539 // deterministic.1540 using InnerKeyTy = std::pair<StringRef, unsigned>;1541 using InnerMapTy = std::map<InnerKeyTy, std::vector<unsigned>>;1542 std::map<unsigned, InnerMapTy> EncMap;1543 1544 for (const auto &[HwModeID, EncodingIDs] : EncodingIDsByHwMode) {1545 for (unsigned EncodingID : EncodingIDs) {1546 const InstructionEncoding &Encoding = Encodings[EncodingID];1547 const unsigned BitWidth =1548 IsVarLenInst ? MaxInstLen : Encoding.getBitWidth();1549 StringRef DecoderNamespace = Encoding.getDecoderNamespace();1550 EncMap[BitWidth][{DecoderNamespace, HwModeID}].push_back(EncodingID);1551 }1552 }1553 1554 // Variable length instructions use the same `APInt` type for all instructions1555 // so we cannot specialize decoders based on instruction bitwidths (which1556 // requires using different `InstType` for differet bitwidths for the correct1557 // template specialization to kick in).1558 if (IsVarLenInst && SpecializeDecodersPerBitwidth)1559 PrintFatalError(1560 "Cannot specialize decoders for variable length instuctions");1561 1562 DecoderContext Ctx;1563 DecoderTreeBuilder TreeBuilder(Ctx, Target, Encodings);1564 1565 DecoderTableInfo TableInfo;1566 DecoderTableEmitter TableEmitter(TableInfo, OS);1567 1568 // Emit a table for each (namespace, hwmode, bitwidth) combination.1569 // Entries in `EncMap` are already sorted by bitwidth. So bucketing per1570 // bitwidth can be done on-the-fly as we iterate over the map.1571 bool HasConflict = false;1572 for (const auto &[BitWidth, BWMap] : EncMap) {1573 for (const auto &[Key, EncodingIDs] : BWMap) {1574 auto [DecoderNamespace, HwModeID] = Key;1575 1576 std::unique_ptr<DecoderTreeNode> Tree =1577 TreeBuilder.buildTree(EncodingIDs);1578 1579 // Skip emitting the table if a conflict has been detected.1580 if (!Tree) {1581 HasConflict = true;1582 continue;1583 }1584 1585 // Form the table name.1586 SmallString<32> TableName({"DecoderTable", DecoderNamespace});1587 if (HwModeID != DefaultMode)1588 TableName.append({"_", Target.getHwModes().getModeName(HwModeID)});1589 TableName.append(utostr(BitWidth));1590 1591 TableEmitter.emitTable(1592 TableName, SpecializeDecodersPerBitwidth ? BitWidth : 0, Tree.get());1593 }1594 1595 // Each BitWidth get's its own decoders and decoder function if1596 // SpecializeDecodersPerBitwidth is enabled.1597 if (SpecializeDecodersPerBitwidth) {1598 emitDecoderFunction(OS, Ctx.Decoders, BitWidth);1599 Ctx.Decoders.clear();1600 }1601 }1602 1603 if (HasConflict)1604 PrintFatalError("Decoding conflict encountered");1605 1606 // Emit the decoder function for the last bucket. This will also emit the1607 // single decoder function if SpecializeDecodersPerBitwidth = false.1608 if (!SpecializeDecodersPerBitwidth)1609 emitDecoderFunction(OS, Ctx.Decoders, 0);1610 1611 // Emit the predicate function.1612 if (TableInfo.HasCheckPredicate)1613 emitPredicateFunction(OS, Ctx.Predicates);1614 1615 // Emit the main entry point for the decoder, decodeInstruction().1616 emitDecodeInstruction(OS, IsVarLenInst, TableInfo);1617 1618 OS << "\n} // namespace\n";1619}1620 1621void llvm::EmitDecoder(const RecordKeeper &RK, raw_ostream &OS) {1622 DecoderEmitter(RK).run(OS);1623}1624