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llvm-project/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp

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//===------------ FixedLenDecoderEmitter.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 length instruction set.
//
//===----------------------------------------------------------------------===//
#include "CodeGenInstruction.h"
#include "CodeGenTarget.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/CachedHashString.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCFixedLenDisassembler.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/LEB128.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"
namespace {
struct EncodingField {
unsigned Base, Width, Offset;
EncodingField(unsigned B, unsigned W, unsigned O)
: Base(B), Width(W), Offset(O) { }
};
struct OperandInfo {
std::vector<EncodingField> Fields;
std::string Decoder;
bool HasCompleteDecoder;
OperandInfo(std::string D, bool HCD)
: Decoder(std::move(D)), HasCompleteDecoder(HCD) {}
void addField(unsigned Base, unsigned Width, unsigned Offset) {
Fields.push_back(EncodingField(Base, Width, Offset));
}
unsigned numFields() const { return Fields.size(); }
typedef std::vector<EncodingField>::const_iterator const_iterator;
const_iterator begin() const { return Fields.begin(); }
const_iterator end() const { return Fields.end(); }
};
typedef std::vector<uint8_t> DecoderTable;
typedef uint32_t DecoderFixup;
typedef std::vector<DecoderFixup> FixupList;
typedef std::vector<FixupList> FixupScopeList;
typedef SmallSetVector<CachedHashString, 16> PredicateSet;
typedef SmallSetVector<CachedHashString, 16> DecoderSet;
struct DecoderTableInfo {
DecoderTable Table;
FixupScopeList FixupStack;
PredicateSet Predicates;
DecoderSet Decoders;
};
struct EncodingAndInst {
const Record *EncodingDef;
const CodeGenInstruction *Inst;
EncodingAndInst(const Record *EncodingDef, const CodeGenInstruction *Inst)
: EncodingDef(EncodingDef), Inst(Inst) {}
};
raw_ostream &operator<<(raw_ostream &OS, const EncodingAndInst &Value) {
if (Value.EncodingDef != Value.Inst->TheDef)
OS << Value.EncodingDef->getName() << ":";
OS << Value.Inst->TheDef->getName();
return OS;
}
class FixedLenDecoderEmitter {
std::vector<EncodingAndInst> NumberedEncodings;
public:
// Defaults preserved here for documentation, even though they aren't
// strictly necessary given the way that this is currently being called.
FixedLenDecoderEmitter(RecordKeeper &R, std::string PredicateNamespace,
std::string GPrefix = "if (",
std::string GPostfix = " == MCDisassembler::Fail)",
std::string ROK = "MCDisassembler::Success",
std::string RFail = "MCDisassembler::Fail",
std::string L = "")
: Target(R), PredicateNamespace(std::move(PredicateNamespace)),
GuardPrefix(std::move(GPrefix)), GuardPostfix(std::move(GPostfix)),
ReturnOK(std::move(ROK)), ReturnFail(std::move(RFail)),
Locals(std::move(L)) {}
// Emit the decoder state machine table.
void emitTable(formatted_raw_ostream &o, DecoderTable &Table,
unsigned Indentation, unsigned BitWidth,
StringRef Namespace) const;
void emitPredicateFunction(formatted_raw_ostream &OS,
PredicateSet &Predicates,
unsigned Indentation) const;
void emitDecoderFunction(formatted_raw_ostream &OS,
DecoderSet &Decoders,
unsigned Indentation) const;
// run - Output the code emitter
void run(raw_ostream &o);
private:
CodeGenTarget Target;
public:
std::string PredicateNamespace;
std::string GuardPrefix, GuardPostfix;
std::string ReturnOK, ReturnFail;
std::string Locals;
};
} // end anonymous namespace
// The set (BIT_TRUE, BIT_FALSE, BIT_UNSET) represents a ternary logic system
// for a bit value.
//
// BIT_UNFILTERED is used as the init value for a filter position. It is used
// only for filter processings.
typedef enum {
BIT_TRUE, // '1'
BIT_FALSE, // '0'
BIT_UNSET, // '?'
BIT_UNFILTERED // unfiltered
} bit_value_t;
static bool ValueSet(bit_value_t V) {
return (V == BIT_TRUE || V == BIT_FALSE);
}
static bool ValueNotSet(bit_value_t V) {
return (V == BIT_UNSET);
}
static int Value(bit_value_t V) {
return ValueNotSet(V) ? -1 : (V == BIT_FALSE ? 0 : 1);
}
static bit_value_t bitFromBits(const BitsInit &bits, unsigned index) {
if (BitInit *bit = dyn_cast<BitInit>(bits.getBit(index)))
return bit->getValue() ? BIT_TRUE : BIT_FALSE;
// The bit is uninitialized.
return BIT_UNSET;
}
// Prints the bit value for each position.
static void dumpBits(raw_ostream &o, const BitsInit &bits) {
for (unsigned index = bits.getNumBits(); index > 0; --index) {
switch (bitFromBits(bits, index - 1)) {
case BIT_TRUE:
o << "1";
break;
case BIT_FALSE:
o << "0";
break;
case BIT_UNSET:
o << "_";
break;
default:
llvm_unreachable("unexpected return value from bitFromBits");
}
}
}
static BitsInit &getBitsField(const Record &def, StringRef str) {
BitsInit *bits = def.getValueAsBitsInit(str);
return *bits;
}
// Representation of the instruction to work on.
typedef std::vector<bit_value_t> insn_t;
namespace {
class FilterChooser;
/// Filter - Filter works with FilterChooser to produce the decoding tree for
/// the ISA.
///
/// It is useful to think of a Filter as governing the switch stmts of the
/// decoding tree in a certain level. Each case stmt delegates to an inferior
/// FilterChooser to decide what further decoding logic to employ, or in another
/// words, what other remaining bits to look at. The FilterChooser eventually
/// chooses a best Filter to do its job.
///
/// This recursive scheme ends when the number of Opcodes assigned to the
/// FilterChooser becomes 1 or if there is a conflict. A conflict happens when
/// the Filter/FilterChooser combo does not know how to distinguish among the
/// Opcodes assigned.
///
/// An example of a conflict is
///
/// Conflict:
/// 111101000.00........00010000....
/// 111101000.00........0001........
/// 1111010...00........0001........
/// 1111010...00....................
/// 1111010.........................
/// 1111............................
/// ................................
/// VST4q8a 111101000_00________00010000____
/// VST4q8b 111101000_00________00010000____
///
/// The Debug output shows the path that the decoding tree follows to reach the
/// the conclusion that there is a conflict. VST4q8a is a vst4 to double-spaced
/// even registers, while VST4q8b is a vst4 to double-spaced odd registers.
///
/// The encoding info in the .td files does not specify this meta information,
/// which could have been used by the decoder to resolve the conflict. The
/// decoder could try to decode the even/odd register numbering and assign to
/// VST4q8a or VST4q8b, but for the time being, the decoder chooses the "a"
/// version and return the Opcode since the two have the same Asm format string.
class Filter {
protected:
const FilterChooser *Owner;// points to the FilterChooser who owns this filter
unsigned StartBit; // the starting bit position
unsigned NumBits; // number of bits to filter
bool Mixed; // a mixed region contains both set and unset bits
// Map of well-known segment value to the set of uid's with that value.
std::map<uint64_t, std::vector<unsigned>> FilteredInstructions;
// Set of uid's with non-constant segment values.
std::vector<unsigned> VariableInstructions;
// Map of well-known segment value to its delegate.
std::map<unsigned, std::unique_ptr<const FilterChooser>> FilterChooserMap;
// Number of instructions which fall under FilteredInstructions category.
unsigned NumFiltered;
// Keeps track of the last opcode in the filtered bucket.
unsigned LastOpcFiltered;
public:
Filter(Filter &&f);
Filter(FilterChooser &owner, unsigned startBit, unsigned numBits, bool mixed);
~Filter() = default;
unsigned getNumFiltered() const { return NumFiltered; }
unsigned getSingletonOpc() const {
assert(NumFiltered == 1);
return LastOpcFiltered;
}
// Return the filter chooser for the group of instructions without constant
// segment values.
const FilterChooser &getVariableFC() const {
assert(NumFiltered == 1);
assert(FilterChooserMap.size() == 1);
return *(FilterChooserMap.find((unsigned)-1)->second);
}
// Divides the decoding task into sub tasks and delegates them to the
// inferior FilterChooser's.
//
// A special case arises when there's only one entry in the filtered
// instructions. In order to unambiguously decode the singleton, we need to
// match the remaining undecoded encoding bits against the singleton.
void recurse();
// Emit table entries to decode instructions given a segment or segments of
// bits.
void emitTableEntry(DecoderTableInfo &TableInfo) const;
// Returns the number of fanout produced by the filter. More fanout implies
// the filter distinguishes more categories of instructions.
unsigned usefulness() const;
}; // end class Filter
} // end anonymous namespace
// These are states of our finite state machines used in FilterChooser's
// filterProcessor() which produces the filter candidates to use.
typedef enum {
ATTR_NONE,
ATTR_FILTERED,
ATTR_ALL_SET,
ATTR_ALL_UNSET,
ATTR_MIXED
} bitAttr_t;
/// 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.
namespace {
class FilterChooser {
protected:
friend class Filter;
// Vector of codegen instructions to choose our filter.
ArrayRef<EncodingAndInst> AllInstructions;
// Vector of uid's for this filter chooser to work on.
const std::vector<unsigned> &Opcodes;
// Lookup table for the operand decoding of instructions.
const std::map<unsigned, std::vector<OperandInfo>> &Operands;
// Vector of candidate filters.
std::vector<Filter> Filters;
// Array of bit values passed down from our parent.
// Set to all BIT_UNFILTERED's for Parent == NULL.
std::vector<bit_value_t> FilterBitValues;
// Links to the FilterChooser above us in the decoding tree.
const FilterChooser *Parent;
// Index of the best filter from Filters.
int BestIndex;
// Width of instructions
unsigned BitWidth;
// Parent emitter
const FixedLenDecoderEmitter *Emitter;
public:
FilterChooser(ArrayRef<EncodingAndInst> Insts,
const std::vector<unsigned> &IDs,
const std::map<unsigned, std::vector<OperandInfo>> &Ops,
unsigned BW, const FixedLenDecoderEmitter *E)
: AllInstructions(Insts), Opcodes(IDs), Operands(Ops),
FilterBitValues(BW, BIT_UNFILTERED), Parent(nullptr), BestIndex(-1),
BitWidth(BW), Emitter(E) {
doFilter();
}
FilterChooser(ArrayRef<EncodingAndInst> Insts,
const std::vector<unsigned> &IDs,
const std::map<unsigned, std::vector<OperandInfo>> &Ops,
const std::vector<bit_value_t> &ParentFilterBitValues,
const FilterChooser &parent)
: AllInstructions(Insts), Opcodes(IDs), Operands(Ops),
FilterBitValues(ParentFilterBitValues), Parent(&parent), BestIndex(-1),
BitWidth(parent.BitWidth), Emitter(parent.Emitter) {
doFilter();
}
FilterChooser(const FilterChooser &) = delete;
void operator=(const FilterChooser &) = delete;
unsigned getBitWidth() const { return BitWidth; }
protected:
// Populates the insn given the uid.
void insnWithID(insn_t &Insn, unsigned Opcode) const {
BitsInit &Bits = getBitsField(*AllInstructions[Opcode].EncodingDef, "Inst");
// We may have a SoftFail bitmask, which specifies a mask where an encoding
// may differ from the value in "Inst" and yet still be valid, but the
// disassembler should return SoftFail instead of Success.
//
// This is used for marking UNPREDICTABLE instructions in the ARM world.
BitsInit *SFBits =
AllInstructions[Opcode].EncodingDef->getValueAsBitsInit("SoftFail");
for (unsigned i = 0; i < BitWidth; ++i) {
if (SFBits && bitFromBits(*SFBits, i) == BIT_TRUE)
Insn.push_back(BIT_UNSET);
else
Insn.push_back(bitFromBits(Bits, i));
}
}
// Populates the field of the insn given the start position and the number of
// consecutive bits to scan for.
//
// Returns false if there exists any uninitialized bit value in the range.
// Returns true, otherwise.
bool fieldFromInsn(uint64_t &Field, insn_t &Insn, unsigned StartBit,
unsigned NumBits) const;
/// dumpFilterArray - dumpFilterArray prints out debugging info for the given
/// filter array as a series of chars.
void dumpFilterArray(raw_ostream &o,
const std::vector<bit_value_t> & filter) const;
/// dumpStack - dumpStack traverses the filter chooser chain and calls
/// dumpFilterArray on each filter chooser up to the top level one.
void dumpStack(raw_ostream &o, const char *prefix) const;
Filter &bestFilter() {
assert(BestIndex != -1 && "BestIndex not set");
return Filters[BestIndex];
}
bool PositionFiltered(unsigned i) const {
return ValueSet(FilterBitValues[i]);
}
// Calculates the island(s) needed to decode the instruction.
// This returns a lit 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.
unsigned getIslands(std::vector<unsigned> &StartBits,
std::vector<unsigned> &EndBits,
std::vector<uint64_t> &FieldVals,
const insn_t &Insn) const;
// Emits code to check the Predicates member of an instruction are true.
// Returns true if predicate matches were emitted, false otherwise.
bool emitPredicateMatch(raw_ostream &o, unsigned &Indentation,
unsigned Opc) const;
bool doesOpcodeNeedPredicate(unsigned Opc) const;
unsigned getPredicateIndex(DecoderTableInfo &TableInfo, StringRef P) const;
void emitPredicateTableEntry(DecoderTableInfo &TableInfo,
unsigned Opc) const;
void emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
unsigned Opc) const;
// Emits table entries to decode the singleton.
void emitSingletonTableEntry(DecoderTableInfo &TableInfo,
unsigned Opc) const;
// Emits code to decode the singleton, and then to decode the rest.
void emitSingletonTableEntry(DecoderTableInfo &TableInfo,
const Filter &Best) const;
void emitBinaryParser(raw_ostream &o, unsigned &Indentation,
const OperandInfo &OpInfo,
bool &OpHasCompleteDecoder) const;
void emitDecoder(raw_ostream &OS, unsigned Indentation, unsigned Opc,
bool &HasCompleteDecoder) const;
unsigned getDecoderIndex(DecoderSet &Decoders, unsigned Opc,
bool &HasCompleteDecoder) const;
// Assign a single filter and run with it.
void runSingleFilter(unsigned startBit, unsigned numBit, bool mixed);
// reportRegion is a helper function for filterProcessor to mark a region as
// eligible for use as a filter region.
void reportRegion(bitAttr_t RA, unsigned StartBit, unsigned BitIndex,
bool AllowMixed);
// FilterProcessor scans the well-known encoding bits of the instructions and
// builds up a list of candidate filters. It chooses the best filter and
// recursively descends down the decoding tree.
bool filterProcessor(bool AllowMixed, bool Greedy = true);
// Decides on the best configuration of filter(s) to use in order to decode
// the instructions. A conflict of instructions may occur, in which case we
// dump the conflict set to the standard error.
void doFilter();
public:
// emitTableEntries - Emit state machine entries to decode our share of
// instructions.
void emitTableEntries(DecoderTableInfo &TableInfo) const;
};
} // end anonymous namespace
///////////////////////////
// //
// Filter Implementation //
// //
///////////////////////////
Filter::Filter(Filter &&f)
: Owner(f.Owner), StartBit(f.StartBit), NumBits(f.NumBits), Mixed(f.Mixed),
FilteredInstructions(std::move(f.FilteredInstructions)),
VariableInstructions(std::move(f.VariableInstructions)),
FilterChooserMap(std::move(f.FilterChooserMap)), NumFiltered(f.NumFiltered),
LastOpcFiltered(f.LastOpcFiltered) {
}
Filter::Filter(FilterChooser &owner, unsigned startBit, unsigned numBits,
bool mixed)
: Owner(&owner), StartBit(startBit), NumBits(numBits), Mixed(mixed) {
assert(StartBit + NumBits - 1 < Owner->BitWidth);
NumFiltered = 0;
LastOpcFiltered = 0;
for (unsigned i = 0, e = Owner->Opcodes.size(); i != e; ++i) {
insn_t Insn;
// Populates the insn given the uid.
Owner->insnWithID(Insn, Owner->Opcodes[i]);
uint64_t Field;
// Scans the segment for possibly well-specified encoding bits.
bool ok = Owner->fieldFromInsn(Field, Insn, StartBit, NumBits);
if (ok) {
// The encoding bits are well-known. Lets add the uid of the
// instruction into the bucket keyed off the constant field value.
LastOpcFiltered = Owner->Opcodes[i];
FilteredInstructions[Field].push_back(LastOpcFiltered);
++NumFiltered;
} else {
// Some of the encoding bit(s) are unspecified. This contributes to
// one additional member of "Variable" instructions.
VariableInstructions.push_back(Owner->Opcodes[i]);
}
}
assert((FilteredInstructions.size() + VariableInstructions.size() > 0)
&& "Filter returns no instruction categories");
}
// Divides the decoding task into sub tasks and delegates them to the
// inferior FilterChooser's.
//
// A special case arises when there's only one entry in the filtered
// instructions. In order to unambiguously decode the singleton, we need to
// match the remaining undecoded encoding bits against the singleton.
void Filter::recurse() {
// Starts by inheriting our parent filter chooser's filter bit values.
std::vector<bit_value_t> BitValueArray(Owner->FilterBitValues);
if (!VariableInstructions.empty()) {
// Conservatively marks each segment position as BIT_UNSET.
for (unsigned bitIndex = 0; bitIndex < NumBits; ++bitIndex)
BitValueArray[StartBit + bitIndex] = BIT_UNSET;
// Delegates to an inferior filter chooser for further processing on this
// group of instructions whose segment values are variable.
FilterChooserMap.insert(
std::make_pair(-1U, llvm::make_unique<FilterChooser>(
Owner->AllInstructions, VariableInstructions,
Owner->Operands, BitValueArray, *Owner)));
}
// No need to recurse for a singleton filtered instruction.
// See also Filter::emit*().
if (getNumFiltered() == 1) {
assert(FilterChooserMap.size() == 1);
return;
}
// Otherwise, create sub choosers.
for (const auto &Inst : FilteredInstructions) {
// Marks all the segment positions with either BIT_TRUE or BIT_FALSE.
for (unsigned bitIndex = 0; bitIndex < NumBits; ++bitIndex) {
if (Inst.first & (1ULL << bitIndex))
BitValueArray[StartBit + bitIndex] = BIT_TRUE;
else
BitValueArray[StartBit + bitIndex] = BIT_FALSE;
}
// Delegates to an inferior filter chooser for further processing on this
// category of instructions.
FilterChooserMap.insert(std::make_pair(
Inst.first, llvm::make_unique<FilterChooser>(
Owner->AllInstructions, Inst.second,
Owner->Operands, BitValueArray, *Owner)));
}
}
static void resolveTableFixups(DecoderTable &Table, const FixupList &Fixups,
uint32_t DestIdx) {
// Any NumToSkip fixups in the current scope can resolve to the
// current location.
for (FixupList::const_reverse_iterator I = Fixups.rbegin(),
E = Fixups.rend();
I != E; ++I) {
// Calculate the distance from the byte following the fixup entry byte
// to the destination. The Target is calculated from after the 16-bit
// NumToSkip entry itself, so subtract two from the displacement here
// to account for that.
uint32_t FixupIdx = *I;
uint32_t Delta = DestIdx - FixupIdx - 3;
// Our NumToSkip entries are 24-bits. Make sure our table isn't too
// big.
assert(Delta < (1u << 24));
Table[FixupIdx] = (uint8_t)Delta;
Table[FixupIdx + 1] = (uint8_t)(Delta >> 8);
Table[FixupIdx + 2] = (uint8_t)(Delta >> 16);
}
}
// Emit table entries to decode instructions given a segment or segments
// of bits.
void Filter::emitTableEntry(DecoderTableInfo &TableInfo) const {
TableInfo.Table.push_back(MCD::OPC_ExtractField);
TableInfo.Table.push_back(StartBit);
TableInfo.Table.push_back(NumBits);
// A new filter entry begins a new scope for fixup resolution.
TableInfo.FixupStack.emplace_back();
DecoderTable &Table = TableInfo.Table;
size_t PrevFilter = 0;
bool HasFallthrough = false;
for (auto &Filter : FilterChooserMap) {
// Field value -1 implies a non-empty set of variable instructions.
// See also recurse().
if (Filter.first == (unsigned)-1) {
HasFallthrough = true;
// Each scope should always have at least one filter value to check
// for.
assert(PrevFilter != 0 && "empty filter set!");
FixupList &CurScope = TableInfo.FixupStack.back();
// Resolve any NumToSkip fixups in the current scope.
resolveTableFixups(Table, CurScope, Table.size());
CurScope.clear();
PrevFilter = 0; // Don't re-process the filter's fallthrough.
} else {
Table.push_back(MCD::OPC_FilterValue);
// Encode and emit the value to filter against.
uint8_t Buffer[16];
unsigned Len = encodeULEB128(Filter.first, Buffer);
Table.insert(Table.end(), Buffer, Buffer + Len);
// Reserve space for the NumToSkip entry. We'll backpatch the value
// later.
PrevFilter = Table.size();
Table.push_back(0);
Table.push_back(0);
Table.push_back(0);
}
// We arrive at a category of instructions with the same segment value.
// Now delegate to the sub filter chooser for further decodings.
// The case may fallthrough, which happens if the remaining well-known
// encoding bits do not match exactly.
Filter.second->emitTableEntries(TableInfo);
// Now that we've emitted the body of the handler, update the NumToSkip
// of the filter itself to be able to skip forward when false. Subtract
// two as to account for the width of the NumToSkip field itself.
if (PrevFilter) {
uint32_t NumToSkip = Table.size() - PrevFilter - 3;
assert(NumToSkip < (1u << 24) && "disassembler decoding table too large!");
Table[PrevFilter] = (uint8_t)NumToSkip;
Table[PrevFilter + 1] = (uint8_t)(NumToSkip >> 8);
Table[PrevFilter + 2] = (uint8_t)(NumToSkip >> 16);
}
}
// Any remaining unresolved fixups bubble up to the parent fixup scope.
assert(TableInfo.FixupStack.size() > 1 && "fixup stack underflow!");
FixupScopeList::iterator Source = TableInfo.FixupStack.end() - 1;
FixupScopeList::iterator Dest = Source - 1;
Dest->insert(Dest->end(), Source->begin(), Source->end());
TableInfo.FixupStack.pop_back();
// If there is no fallthrough, then the final filter should get fixed
// up according to the enclosing scope rather than the current position.
if (!HasFallthrough)
TableInfo.FixupStack.back().push_back(PrevFilter);
}
// Returns the number of fanout produced by the filter. More fanout implies
// the filter distinguishes more categories of instructions.
unsigned Filter::usefulness() const {
if (!VariableInstructions.empty())
return FilteredInstructions.size();
else
return FilteredInstructions.size() + 1;
}
//////////////////////////////////
// //
// Filterchooser Implementation //
// //
//////////////////////////////////
// Emit the decoder state machine table.
void FixedLenDecoderEmitter::emitTable(formatted_raw_ostream &OS,
DecoderTable &Table,
unsigned Indentation,
unsigned BitWidth,
StringRef Namespace) const {
OS.indent(Indentation) << "static const uint8_t DecoderTable" << Namespace
<< BitWidth << "[] = {\n";
Indentation += 2;
// FIXME: We may be able to use the NumToSkip values to recover
// appropriate indentation levels.
DecoderTable::const_iterator I = Table.begin();
DecoderTable::const_iterator E = Table.end();
while (I != E) {
assert (I < E && "incomplete decode table entry!");
uint64_t Pos = I - Table.begin();
OS << "/* " << Pos << " */";
OS.PadToColumn(12);
switch (*I) {
default:
PrintFatalError("invalid decode table opcode");
case MCD::OPC_ExtractField: {
++I;
unsigned Start = *I++;
unsigned Len = *I++;
OS.indent(Indentation) << "MCD::OPC_ExtractField, " << Start << ", "
<< Len << ", // Inst{";
if (Len > 1)
OS << (Start + Len - 1) << "-";
OS << Start << "} ...\n";
break;
}
case MCD::OPC_FilterValue: {
++I;
OS.indent(Indentation) << "MCD::OPC_FilterValue, ";
// The filter value is ULEB128 encoded.
while (*I >= 128)
OS << (unsigned)*I++ << ", ";
OS << (unsigned)*I++ << ", ";
// 24-bit numtoskip value.
uint8_t Byte = *I++;
uint32_t NumToSkip = Byte;
OS << (unsigned)Byte << ", ";
Byte = *I++;
OS << (unsigned)Byte << ", ";
NumToSkip |= Byte << 8;
Byte = *I++;
OS << utostr(Byte) << ", ";
NumToSkip |= Byte << 16;
OS << "// Skip to: " << ((I - Table.begin()) + NumToSkip) << "\n";
break;
}
case MCD::OPC_CheckField: {
++I;
unsigned Start = *I++;
unsigned Len = *I++;
OS.indent(Indentation) << "MCD::OPC_CheckField, " << Start << ", "
<< Len << ", ";// << Val << ", " << NumToSkip << ",\n";
// ULEB128 encoded field value.
for (; *I >= 128; ++I)
OS << (unsigned)*I << ", ";
OS << (unsigned)*I++ << ", ";
// 24-bit numtoskip value.
uint8_t Byte = *I++;
uint32_t NumToSkip = Byte;
OS << (unsigned)Byte << ", ";
Byte = *I++;
OS << (unsigned)Byte << ", ";
NumToSkip |= Byte << 8;
Byte = *I++;
OS << utostr(Byte) << ", ";
NumToSkip |= Byte << 16;
OS << "// Skip to: " << ((I - Table.begin()) + NumToSkip) << "\n";
break;
}
case MCD::OPC_CheckPredicate: {
++I;
OS.indent(Indentation) << "MCD::OPC_CheckPredicate, ";
for (; *I >= 128; ++I)
OS << (unsigned)*I << ", ";
OS << (unsigned)*I++ << ", ";
// 24-bit numtoskip value.
uint8_t Byte = *I++;
uint32_t NumToSkip = Byte;
OS << (unsigned)Byte << ", ";
Byte = *I++;
OS << (unsigned)Byte << ", ";
NumToSkip |= Byte << 8;
Byte = *I++;
OS << utostr(Byte) << ", ";
NumToSkip |= Byte << 16;
OS << "// Skip to: " << ((I - Table.begin()) + NumToSkip) << "\n";
break;
}
case MCD::OPC_Decode:
case MCD::OPC_TryDecode: {
bool IsTry = *I == MCD::OPC_TryDecode;
++I;
// Extract the ULEB128 encoded Opcode to a buffer.
uint8_t Buffer[16], *p = Buffer;
while ((*p++ = *I++) >= 128)
assert((p - Buffer) <= (ptrdiff_t)sizeof(Buffer)
&& "ULEB128 value too large!");
// Decode the Opcode value.
unsigned Opc = decodeULEB128(Buffer);
OS.indent(Indentation) << "MCD::OPC_" << (IsTry ? "Try" : "")
<< "Decode, ";
for (p = Buffer; *p >= 128; ++p)
OS << (unsigned)*p << ", ";
OS << (unsigned)*p << ", ";
// Decoder index.
for (; *I >= 128; ++I)
OS << (unsigned)*I << ", ";
OS << (unsigned)*I++ << ", ";
if (!IsTry) {
OS << "// Opcode: " << NumberedEncodings[Opc] << "\n";
break;
}
// Fallthrough for OPC_TryDecode.
// 24-bit numtoskip value.
uint8_t Byte = *I++;
uint32_t NumToSkip = Byte;
OS << (unsigned)Byte << ", ";
Byte = *I++;
OS << (unsigned)Byte << ", ";
NumToSkip |= Byte << 8;
Byte = *I++;
OS << utostr(Byte) << ", ";
NumToSkip |= Byte << 16;
OS << "// Opcode: " << NumberedEncodings[Opc]
<< ", skip to: " << ((I - Table.begin()) + NumToSkip) << "\n";
break;
}
case MCD::OPC_SoftFail: {
++I;
OS.indent(Indentation) << "MCD::OPC_SoftFail";
// Positive mask
uint64_t Value = 0;
unsigned Shift = 0;
do {
OS << ", " << (unsigned)*I;
Value += (*I & 0x7f) << Shift;
Shift += 7;
} while (*I++ >= 128);
if (Value > 127) {
OS << " /* 0x";
OS.write_hex(Value);
OS << " */";
}
// Negative mask
Value = 0;
Shift = 0;
do {
OS << ", " << (unsigned)*I;
Value += (*I & 0x7f) << Shift;
Shift += 7;
} while (*I++ >= 128);
if (Value > 127) {
OS << " /* 0x";
OS.write_hex(Value);
OS << " */";
}
OS << ",\n";
break;
}
case MCD::OPC_Fail: {
++I;
OS.indent(Indentation) << "MCD::OPC_Fail,\n";
break;
}
}
}
OS.indent(Indentation) << "0\n";
Indentation -= 2;
OS.indent(Indentation) << "};\n\n";
}
void FixedLenDecoderEmitter::
emitPredicateFunction(formatted_raw_ostream &OS, PredicateSet &Predicates,
unsigned Indentation) const {
// The predicate function is just a big switch statement based on the
// input predicate index.
OS.indent(Indentation) << "static bool checkDecoderPredicate(unsigned Idx, "
<< "const FeatureBitset& Bits) {\n";
Indentation += 2;
if (!Predicates.empty()) {
OS.indent(Indentation) << "switch (Idx) {\n";
OS.indent(Indentation) << "default: llvm_unreachable(\"Invalid index!\");\n";
unsigned Index = 0;
for (const auto &Predicate : Predicates) {
OS.indent(Indentation) << "case " << Index++ << ":\n";
OS.indent(Indentation+2) << "return (" << Predicate << ");\n";
}
OS.indent(Indentation) << "}\n";
} else {
// No case statement to emit
OS.indent(Indentation) << "llvm_unreachable(\"Invalid index!\");\n";
}
Indentation -= 2;
OS.indent(Indentation) << "}\n\n";
}
void FixedLenDecoderEmitter::
emitDecoderFunction(formatted_raw_ostream &OS, DecoderSet &Decoders,
unsigned Indentation) const {
// The decoder function is just a big switch statement based on the
// input decoder index.
OS.indent(Indentation) << "template<typename InsnType>\n";
OS.indent(Indentation) << "static DecodeStatus decodeToMCInst(DecodeStatus S,"
<< " unsigned Idx, InsnType insn, MCInst &MI,\n";
OS.indent(Indentation) << " uint64_t "
<< "Address, const void *Decoder, bool &DecodeComplete) {\n";
Indentation += 2;
OS.indent(Indentation) << "DecodeComplete = true;\n";
OS.indent(Indentation) << "InsnType tmp;\n";
OS.indent(Indentation) << "switch (Idx) {\n";
OS.indent(Indentation) << "default: llvm_unreachable(\"Invalid index!\");\n";
unsigned Index = 0;
for (const auto &Decoder : Decoders) {
OS.indent(Indentation) << "case " << Index++ << ":\n";
OS << Decoder;
OS.indent(Indentation+2) << "return S;\n";
}
OS.indent(Indentation) << "}\n";
Indentation -= 2;
OS.indent(Indentation) << "}\n\n";
}
// Populates the field of the insn given the start position and the number of
// consecutive bits to scan for.
//
// Returns false if and on the first uninitialized bit value encountered.
// Returns true, otherwise.
bool FilterChooser::fieldFromInsn(uint64_t &Field, insn_t &Insn,
unsigned StartBit, unsigned NumBits) const {
Field = 0;
for (unsigned i = 0; i < NumBits; ++i) {
if (Insn[StartBit + i] == BIT_UNSET)
return false;
if (Insn[StartBit + i] == BIT_TRUE)
Field = Field | (1ULL << i);
}
return true;
}
/// dumpFilterArray - dumpFilterArray prints out debugging info for the given
/// filter array as a series of chars.
void FilterChooser::dumpFilterArray(raw_ostream &o,
const std::vector<bit_value_t> &filter) const {
for (unsigned bitIndex = BitWidth; bitIndex > 0; bitIndex--) {
switch (filter[bitIndex - 1]) {
case BIT_UNFILTERED:
o << ".";
break;
case BIT_UNSET:
o << "_";
break;
case BIT_TRUE:
o << "1";
break;
case BIT_FALSE:
o << "0";
break;
}
}
}
/// 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 &o, const char *prefix) const {
const FilterChooser *current = this;
while (current) {
o << prefix;
dumpFilterArray(o, current->FilterBitValues);
o << '\n';
current = current->Parent;
}
}
// 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.
unsigned FilterChooser::getIslands(std::vector<unsigned> &StartBits,
std::vector<unsigned> &EndBits,
std::vector<uint64_t> &FieldVals,
const insn_t &Insn) const {
unsigned Num, BitNo;
Num = BitNo = 0;
uint64_t FieldVal = 0;
// 0: Init
// 1: Water (the bit value does not affect decoding)
// 2: Island (well-known bit value needed for decoding)
int State = 0;
int Val = -1;
for (unsigned i = 0; i < BitWidth; ++i) {
Val = Value(Insn[i]);
bool Filtered = PositionFiltered(i);
switch (State) {
default: llvm_unreachable("Unreachable code!");
case 0:
case 1:
if (Filtered || Val == -1)
State = 1; // Still in Water
else {
State = 2; // Into the Island
BitNo = 0;
StartBits.push_back(i);
FieldVal = Val;
}
break;
case 2:
if (Filtered || Val == -1) {
State = 1; // Into the Water
EndBits.push_back(i - 1);
FieldVals.push_back(FieldVal);
++Num;
} else {
State = 2; // Still in Island
++BitNo;
FieldVal = FieldVal | Val << BitNo;
}
break;
}
}
// If we are still in Island after the loop, do some housekeeping.
if (State == 2) {
EndBits.push_back(BitWidth - 1);
FieldVals.push_back(FieldVal);
++Num;
}
assert(StartBits.size() == Num && EndBits.size() == Num &&
FieldVals.size() == Num);
return Num;
}
void FilterChooser::emitBinaryParser(raw_ostream &o, unsigned &Indentation,
const OperandInfo &OpInfo,
bool &OpHasCompleteDecoder) const {
const std::string &Decoder = OpInfo.Decoder;
if (OpInfo.numFields() != 1)
o.indent(Indentation) << "tmp = 0;\n";
for (const EncodingField &EF : OpInfo) {
o.indent(Indentation) << "tmp ";
if (OpInfo.numFields() != 1) o << '|';
o << "= fieldFromInstruction"
<< "(insn, " << EF.Base << ", " << EF.Width << ')';
if (OpInfo.numFields() != 1 || EF.Offset != 0)
o << " << " << EF.Offset;
o << ";\n";
}
if (Decoder != "") {
OpHasCompleteDecoder = OpInfo.HasCompleteDecoder;
o.indent(Indentation) << Emitter->GuardPrefix << Decoder
<< "(MI, tmp, Address, Decoder)"
<< Emitter->GuardPostfix
<< " { " << (OpHasCompleteDecoder ? "" : "DecodeComplete = false; ")
<< "return MCDisassembler::Fail; }\n";
} else {
OpHasCompleteDecoder = true;
o.indent(Indentation) << "MI.addOperand(MCOperand::createImm(tmp));\n";
}
}
void FilterChooser::emitDecoder(raw_ostream &OS, unsigned Indentation,
unsigned Opc, bool &HasCompleteDecoder) const {
HasCompleteDecoder = true;
for (const auto &Op : Operands.find(Opc)->second) {
// If a custom instruction decoder was specified, use that.
if (Op.numFields() == 0 && !Op.Decoder.empty()) {
HasCompleteDecoder = Op.HasCompleteDecoder;
OS.indent(Indentation) << Emitter->GuardPrefix << Op.Decoder
<< "(MI, insn, Address, Decoder)"
<< Emitter->GuardPostfix
<< " { " << (HasCompleteDecoder ? "" : "DecodeComplete = false; ")
<< "return MCDisassembler::Fail; }\n";
break;
}
bool OpHasCompleteDecoder;
emitBinaryParser(OS, Indentation, Op, OpHasCompleteDecoder);
if (!OpHasCompleteDecoder)
HasCompleteDecoder = false;
}
}
unsigned FilterChooser::getDecoderIndex(DecoderSet &Decoders,
unsigned Opc,
bool &HasCompleteDecoder) const {
// Build up the predicate string.
SmallString<256> Decoder;
// FIXME: emitDecoder() function can take a buffer directly rather than
// a stream.
raw_svector_ostream S(Decoder);
unsigned I = 4;
emitDecoder(S, I, Opc, HasCompleteDecoder);
// Using the full decoder string as the key value here is a bit
// heavyweight, but is effective. If the string comparisons become a
// performance concern, we can implement a mangling of the predicate
// data easily enough with a map back to the actual string. That's
// overkill for now, though.
// Make sure the predicate is in the table.
Decoders.insert(CachedHashString(Decoder));
// Now figure out the index for when we write out the table.
DecoderSet::const_iterator P = find(Decoders, Decoder.str());
return (unsigned)(P - Decoders.begin());
}
static void emitSinglePredicateMatch(raw_ostream &o, StringRef str,
const std::string &PredicateNamespace) {
if (str[0] == '!')
o << "!Bits[" << PredicateNamespace << "::"
<< str.slice(1,str.size()) << "]";
else
o << "Bits[" << PredicateNamespace << "::" << str << "]";
}
bool FilterChooser::emitPredicateMatch(raw_ostream &o, unsigned &Indentation,
unsigned Opc) const {
ListInit *Predicates =
AllInstructions[Opc].EncodingDef->getValueAsListInit("Predicates");
bool IsFirstEmission = true;
for (unsigned i = 0; i < Predicates->size(); ++i) {
Record *Pred = Predicates->getElementAsRecord(i);
if (!Pred->getValue("AssemblerMatcherPredicate"))
continue;
StringRef P = Pred->getValueAsString("AssemblerCondString");
if (P.empty())
continue;
if (!IsFirstEmission)
o << " && ";
std::pair<StringRef, StringRef> pairs = P.split(',');
while (!pairs.second.empty()) {
emitSinglePredicateMatch(o, pairs.first, Emitter->PredicateNamespace);
o << " && ";
pairs = pairs.second.split(',');
}
emitSinglePredicateMatch(o, pairs.first, Emitter->PredicateNamespace);
IsFirstEmission = false;
}
return !Predicates->empty();
}
bool FilterChooser::doesOpcodeNeedPredicate(unsigned Opc) const {
ListInit *Predicates =
AllInstructions[Opc].EncodingDef->getValueAsListInit("Predicates");
for (unsigned i = 0; i < Predicates->size(); ++i) {
Record *Pred = Predicates->getElementAsRecord(i);
if (!Pred->getValue("AssemblerMatcherPredicate"))
continue;
StringRef P = Pred->getValueAsString("AssemblerCondString");
if (P.empty())
continue;
return true;
}
return false;
}
unsigned FilterChooser::getPredicateIndex(DecoderTableInfo &TableInfo,
StringRef Predicate) const {
// Using the full predicate string as the key value here is a bit
// heavyweight, but is effective. If the string comparisons become a
// performance concern, we can implement a mangling of the predicate
// data easily enough with a map back to the actual string. That's
// overkill for now, though.
// Make sure the predicate is in the table.
TableInfo.Predicates.insert(CachedHashString(Predicate));
// Now figure out the index for when we write out the table.
PredicateSet::const_iterator P = find(TableInfo.Predicates, Predicate);
return (unsigned)(P - TableInfo.Predicates.begin());
}
void FilterChooser::emitPredicateTableEntry(DecoderTableInfo &TableInfo,
unsigned Opc) const {
if (!doesOpcodeNeedPredicate(Opc))
return;
// Build up the predicate string.
SmallString<256> Predicate;
// FIXME: emitPredicateMatch() functions can take a buffer directly rather
// than a stream.
raw_svector_ostream PS(Predicate);
unsigned I = 0;
emitPredicateMatch(PS, I, Opc);
// Figure out the index into the predicate table for the predicate just
// computed.
unsigned PIdx = getPredicateIndex(TableInfo, PS.str());
SmallString<16> PBytes;
raw_svector_ostream S(PBytes);
encodeULEB128(PIdx, S);
TableInfo.Table.push_back(MCD::OPC_CheckPredicate);
// Predicate index
for (unsigned i = 0, e = PBytes.size(); i != e; ++i)
TableInfo.Table.push_back(PBytes[i]);
// Push location for NumToSkip backpatching.
TableInfo.FixupStack.back().push_back(TableInfo.Table.size());
TableInfo.Table.push_back(0);
TableInfo.Table.push_back(0);
TableInfo.Table.push_back(0);
}
void FilterChooser::emitSoftFailTableEntry(DecoderTableInfo &TableInfo,
unsigned Opc) const {
BitsInit *SFBits =
AllInstructions[Opc].EncodingDef->getValueAsBitsInit("SoftFail");
if (!SFBits) return;
BitsInit *InstBits =
AllInstructions[Opc].EncodingDef->getValueAsBitsInit("Inst");
APInt PositiveMask(BitWidth, 0ULL);
APInt NegativeMask(BitWidth, 0ULL);
for (unsigned i = 0; i < BitWidth; ++i) {
bit_value_t B = bitFromBits(*SFBits, i);
bit_value_t IB = bitFromBits(*InstBits, i);
if (B != BIT_TRUE) continue;
switch (IB) {
case BIT_FALSE:
// The bit is meant to be false, so emit a check to see if it is true.
PositiveMask.setBit(i);
break;
case BIT_TRUE:
// The bit is meant to be true, so emit a check to see if it is false.
NegativeMask.setBit(i);
break;
default:
// The bit is not set; this must be an error!
errs() << "SoftFail Conflict: bit SoftFail{" << i << "} in "
<< AllInstructions[Opc] << " is set but Inst{" << i
<< "} is unset!\n"
<< " - You can only mark a bit as SoftFail if it is fully defined"
<< " (1/0 - not '?') in Inst\n";
return;
}
}
bool NeedPositiveMask = PositiveMask.getBoolValue();
bool NeedNegativeMask = NegativeMask.getBoolValue();
if (!NeedPositiveMask && !NeedNegativeMask)
return;
TableInfo.Table.push_back(MCD::OPC_SoftFail);
SmallString<16> MaskBytes;
raw_svector_ostream S(MaskBytes);
if (NeedPositiveMask) {
encodeULEB128(PositiveMask.getZExtValue(), S);
for (unsigned i = 0, e = MaskBytes.size(); i != e; ++i)
TableInfo.Table.push_back(MaskBytes[i]);
} else
TableInfo.Table.push_back(0);
if (NeedNegativeMask) {
MaskBytes.clear();
encodeULEB128(NegativeMask.getZExtValue(), S);
for (unsigned i = 0, e = MaskBytes.size(); i != e; ++i)
TableInfo.Table.push_back(MaskBytes[i]);
} else
TableInfo.Table.push_back(0);
}
// Emits table entries to decode the singleton.
void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
unsigned Opc) const {
std::vector<unsigned> StartBits;
std::vector<unsigned> EndBits;
std::vector<uint64_t> FieldVals;
insn_t Insn;
insnWithID(Insn, Opc);
// Look for islands of undecoded bits of the singleton.
getIslands(StartBits, EndBits, FieldVals, Insn);
unsigned Size = StartBits.size();
// Emit the predicate table entry if one is needed.
emitPredicateTableEntry(TableInfo, Opc);
// Check any additional encoding fields needed.
for (unsigned I = Size; I != 0; --I) {
unsigned NumBits = EndBits[I-1] - StartBits[I-1] + 1;
TableInfo.Table.push_back(MCD::OPC_CheckField);
TableInfo.Table.push_back(StartBits[I-1]);
TableInfo.Table.push_back(NumBits);
uint8_t Buffer[16], *p;
encodeULEB128(FieldVals[I-1], Buffer);
for (p = Buffer; *p >= 128 ; ++p)
TableInfo.Table.push_back(*p);
TableInfo.Table.push_back(*p);
// Push location for NumToSkip backpatching.
TableInfo.FixupStack.back().push_back(TableInfo.Table.size());
// The fixup is always 24-bits, so go ahead and allocate the space
// in the table so all our relative position calculations work OK even
// before we fully resolve the real value here.
TableInfo.Table.push_back(0);
TableInfo.Table.push_back(0);
TableInfo.Table.push_back(0);
}
// Check for soft failure of the match.
emitSoftFailTableEntry(TableInfo, Opc);
bool HasCompleteDecoder;
unsigned DIdx = getDecoderIndex(TableInfo.Decoders, Opc, HasCompleteDecoder);
// Produce OPC_Decode or OPC_TryDecode opcode based on the information
// whether the instruction decoder is complete or not. If it is complete
// then it handles all possible values of remaining variable/unfiltered bits
// and for any value can determine if the bitpattern is a valid instruction
// or not. This means OPC_Decode will be the final step in the decoding
// process. If it is not complete, then the Fail return code from the
// decoder method indicates that additional processing should be done to see
// if there is any other instruction that also matches the bitpattern and
// can decode it.
TableInfo.Table.push_back(HasCompleteDecoder ? MCD::OPC_Decode :
MCD::OPC_TryDecode);
uint8_t Buffer[16], *p;
encodeULEB128(Opc, Buffer);
for (p = Buffer; *p >= 128 ; ++p)
TableInfo.Table.push_back(*p);
TableInfo.Table.push_back(*p);
SmallString<16> Bytes;
raw_svector_ostream S(Bytes);
encodeULEB128(DIdx, S);
// Decoder index
for (unsigned i = 0, e = Bytes.size(); i != e; ++i)
TableInfo.Table.push_back(Bytes[i]);
if (!HasCompleteDecoder) {
// Push location for NumToSkip backpatching.
TableInfo.FixupStack.back().push_back(TableInfo.Table.size());
// Allocate the space for the fixup.
TableInfo.Table.push_back(0);
TableInfo.Table.push_back(0);
TableInfo.Table.push_back(0);
}
}
// Emits table entries to decode the singleton, and then to decode the rest.
void FilterChooser::emitSingletonTableEntry(DecoderTableInfo &TableInfo,
const Filter &Best) const {
unsigned Opc = Best.getSingletonOpc();
// complex singletons need predicate checks from the first singleton
// to refer forward to the variable filterchooser that follows.
TableInfo.FixupStack.emplace_back();
emitSingletonTableEntry(TableInfo, Opc);
resolveTableFixups(TableInfo.Table, TableInfo.FixupStack.back(),
TableInfo.Table.size());
TableInfo.FixupStack.pop_back();
Best.getVariableFC().emitTableEntries(TableInfo);
}
// Assign a single filter and run with it. Top level API client can initialize
// with a single filter to start the filtering process.
void FilterChooser::runSingleFilter(unsigned startBit, unsigned numBit,
bool mixed) {
Filters.clear();
Filters.emplace_back(*this, startBit, numBit, true);
BestIndex = 0; // Sole Filter instance to choose from.
bestFilter().recurse();
}
// reportRegion is a helper function for filterProcessor to mark a region as
// eligible for use as a filter region.
void FilterChooser::reportRegion(bitAttr_t RA, unsigned StartBit,
unsigned BitIndex, bool AllowMixed) {
if (RA == ATTR_MIXED && AllowMixed)
Filters.emplace_back(*this, StartBit, BitIndex - StartBit, true);
else if (RA == ATTR_ALL_SET && !AllowMixed)
Filters.emplace_back(*this, StartBit, BitIndex - StartBit, false);
}
// FilterProcessor scans the well-known encoding bits of the instructions and
// builds up a list of candidate filters. It chooses the best filter and
// recursively descends down the decoding tree.
bool FilterChooser::filterProcessor(bool AllowMixed, bool Greedy) {
Filters.clear();
BestIndex = -1;
unsigned numInstructions = Opcodes.size();
assert(numInstructions && "Filter created with no instructions");
// No further filtering is necessary.
if (numInstructions == 1)
return true;
// Heuristics. See also doFilter()'s "Heuristics" comment when num of
// instructions is 3.
if (AllowMixed && !Greedy) {
assert(numInstructions == 3);
for (unsigned i = 0; i < Opcodes.size(); ++i) {
std::vector<unsigned> StartBits;
std::vector<unsigned> EndBits;
std::vector<uint64_t> FieldVals;
insn_t Insn;
insnWithID(Insn, Opcodes[i]);
// Look for islands of undecoded bits of any instruction.
if (getIslands(StartBits, EndBits, FieldVals, Insn) > 0) {
// Found an instruction with island(s). Now just assign a filter.
runSingleFilter(StartBits[0], EndBits[0] - StartBits[0] + 1, true);
return true;
}
}
}
unsigned BitIndex;
// We maintain BIT_WIDTH copies of the bitAttrs automaton.
// The automaton consumes the corresponding bit from each
// instruction.
//
// Input symbols: 0, 1, and _ (unset).
// 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)
std::vector<bitAttr_t> bitAttrs;
// FILTERED bit positions provide no entropy and are not worthy of pursuing.
// Filter::recurse() set either BIT_TRUE or BIT_FALSE for each position.
for (BitIndex = 0; BitIndex < BitWidth; ++BitIndex)
if (FilterBitValues[BitIndex] == BIT_TRUE ||
FilterBitValues[BitIndex] == BIT_FALSE)
bitAttrs.push_back(ATTR_FILTERED);
else
bitAttrs.push_back(ATTR_NONE);
for (unsigned InsnIndex = 0; InsnIndex < numInstructions; ++InsnIndex) {
insn_t insn;
insnWithID(insn, Opcodes[InsnIndex]);
for (BitIndex = 0; BitIndex < BitWidth; ++BitIndex) {
switch (bitAttrs[BitIndex]) {
case ATTR_NONE:
if (insn[BitIndex] == BIT_UNSET)
bitAttrs[BitIndex] = ATTR_ALL_UNSET;
else
bitAttrs[BitIndex] = ATTR_ALL_SET;
break;
case ATTR_ALL_SET:
if (insn[BitIndex] == BIT_UNSET)
bitAttrs[BitIndex] = ATTR_MIXED;
break;
case ATTR_ALL_UNSET:
if (insn[BitIndex] != BIT_UNSET)
bitAttrs[BitIndex] = ATTR_MIXED;
break;
case ATTR_MIXED:
case ATTR_FILTERED:
break;
}
}
}
// 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;
for (BitIndex = 0; BitIndex < BitWidth; ++BitIndex) {
bitAttr_t bitAttr = bitAttrs[BitIndex];
assert(bitAttr != ATTR_NONE && "Bit without attributes");
switch (RA) {
case ATTR_NONE:
switch (bitAttr) {
case ATTR_FILTERED:
break;
case ATTR_ALL_SET:
StartBit = BitIndex;
RA = ATTR_ALL_SET;
break;
case ATTR_ALL_UNSET:
break;
case ATTR_MIXED:
StartBit = BitIndex;
RA = ATTR_MIXED;
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_ALL_SET:
switch (bitAttr) {
case ATTR_FILTERED:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
RA = ATTR_NONE;
break;
case ATTR_ALL_SET:
break;
case ATTR_ALL_UNSET:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
RA = ATTR_NONE;
break;
case ATTR_MIXED:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
StartBit = BitIndex;
RA = ATTR_MIXED;
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_MIXED:
switch (bitAttr) {
case ATTR_FILTERED:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
StartBit = BitIndex;
RA = ATTR_NONE;
break;
case ATTR_ALL_SET:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
StartBit = BitIndex;
RA = ATTR_ALL_SET;
break;
case ATTR_ALL_UNSET:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
RA = ATTR_NONE;
break;
case ATTR_MIXED:
break;
default:
llvm_unreachable("Unexpected bitAttr!");
}
break;
case ATTR_ALL_UNSET:
llvm_unreachable("regionAttr state machine has no ATTR_UNSET state");
case ATTR_FILTERED:
llvm_unreachable("regionAttr state machine has no ATTR_FILTERED state");
}
}
// At the end, if we're still in ALL_SET or MIXED states, report a region
switch (RA) {
case ATTR_NONE:
break;
case ATTR_FILTERED:
break;
case ATTR_ALL_SET:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
break;
case ATTR_ALL_UNSET:
break;
case ATTR_MIXED:
reportRegion(RA, StartBit, BitIndex, AllowMixed);
break;
}
// We have finished with the filter processings. Now it's time to choose
// the best performing filter.
BestIndex = 0;
bool AllUseless = true;
unsigned BestScore = 0;
for (unsigned i = 0, e = Filters.size(); i != e; ++i) {
unsigned Usefulness = Filters[i].usefulness();
if (Usefulness)
AllUseless = false;
if (Usefulness > BestScore) {
BestIndex = i;
BestScore = Usefulness;
}
}
if (!AllUseless)
bestFilter().recurse();
return !AllUseless;
} // end of FilterChooser::filterProcessor(bool)
// Decides on the best configuration of filter(s) to use in order to decode
// the instructions. A conflict of instructions may occur, in which case we
// dump the conflict set to the standard error.
void FilterChooser::doFilter() {
unsigned Num = Opcodes.size();
assert(Num && "FilterChooser created with no instructions");
// Try regions of consecutive known bit values first.
if (filterProcessor(false))
return;
// Then regions of mixed bits (both known and unitialized bit values allowed).
if (filterProcessor(true))
return;
// Heuristics to cope with conflict set {t2CMPrs, t2SUBSrr, t2SUBSrs} where
// no single instruction for the maximum ATTR_MIXED region Inst{14-4} has a
// well-known encoding pattern. In such case, we backtrack and scan for the
// the very first consecutive ATTR_ALL_SET region and assign a filter to it.
if (Num == 3 && filterProcessor(true, false))
return;
// If we come to here, the instruction decoding has failed.
// Set the BestIndex to -1 to indicate so.
BestIndex = -1;
}
// emitTableEntries - Emit state machine entries to decode our share of
// instructions.
void FilterChooser::emitTableEntries(DecoderTableInfo &TableInfo) const {
if (Opcodes.size() == 1) {
// There is only one instruction in the set, which is great!
// Call emitSingletonDecoder() to see whether there are any remaining
// encodings bits.
emitSingletonTableEntry(TableInfo, Opcodes[0]);
return;
}
// Choose the best filter to do the decodings!
if (BestIndex != -1) {
const Filter &Best = Filters[BestIndex];
if (Best.getNumFiltered() == 1)
emitSingletonTableEntry(TableInfo, Best);
else
Best.emitTableEntry(TableInfo);
return;
}
// We don't know how to decode these instructions! Dump the
// conflict set and bail.
// Print out useful conflict information for postmortem analysis.
errs() << "Decoding Conflict:\n";
dumpStack(errs(), "\t\t");
for (unsigned i = 0; i < Opcodes.size(); ++i) {
errs() << '\t' << AllInstructions[Opcodes[i]] << " ";
dumpBits(errs(),
getBitsField(*AllInstructions[Opcodes[i]].EncodingDef, "Inst"));
errs() << '\n';
}
}
static std::string findOperandDecoderMethod(TypedInit *TI) {
std::string Decoder;
Record *Record = cast<DefInit>(TI)->getDef();
RecordVal *DecoderString = Record->getValue("DecoderMethod");
StringInit *String = DecoderString ?
dyn_cast<StringInit>(DecoderString->getValue()) : nullptr;
if (String) {
Decoder = String->getValue();
if (!Decoder.empty())
return Decoder;
}
if (Record->isSubClassOf("RegisterOperand"))
Record = Record->getValueAsDef("RegClass");
if (Record->isSubClassOf("RegisterClass")) {
Decoder = "Decode" + Record->getName().str() + "RegisterClass";
} else if (Record->isSubClassOf("PointerLikeRegClass")) {
Decoder = "DecodePointerLikeRegClass" +
utostr(Record->getValueAsInt("RegClassKind"));
}
return Decoder;
}
static bool populateInstruction(CodeGenTarget &Target,
const CodeGenInstruction &CGI, unsigned Opc,
std::map<unsigned, std::vector<OperandInfo>> &Operands){
const Record &Def = *CGI.TheDef;
// If all the bit positions are not specified; do not decode this instruction.
// We are bound to fail! For proper disassembly, the well-known encoding bits
// of the instruction must be fully specified.
BitsInit &Bits = getBitsField(Def, "Inst");
if (Bits.allInComplete()) return false;
std::vector<OperandInfo> InsnOperands;
// If the instruction has specified a custom decoding hook, use that instead
// of trying to auto-generate the decoder.
StringRef InstDecoder = Def.getValueAsString("DecoderMethod");
if (InstDecoder != "") {
bool HasCompleteInstDecoder = Def.getValueAsBit("hasCompleteDecoder");
InsnOperands.push_back(OperandInfo(InstDecoder, HasCompleteInstDecoder));
Operands[Opc] = InsnOperands;
return true;
}
// Generate a description of the operand of the instruction that we know
// how to decode automatically.
// FIXME: We'll need to have a way to manually override this as needed.
// Gather the outputs/inputs of the instruction, so we can find their
// positions in the encoding. This assumes for now that they appear in the
// MCInst in the order that they're listed.
std::vector<std::pair<Init*, StringRef>> InOutOperands;
DagInit *Out = Def.getValueAsDag("OutOperandList");
DagInit *In = Def.getValueAsDag("InOperandList");
for (unsigned i = 0; i < Out->getNumArgs(); ++i)
InOutOperands.push_back(std::make_pair(Out->getArg(i),
Out->getArgNameStr(i)));
for (unsigned i = 0; i < In->getNumArgs(); ++i)
InOutOperands.push_back(std::make_pair(In->getArg(i),
In->getArgNameStr(i)));
// Search for tied operands, so that we can correctly instantiate
// operands that are not explicitly represented in the encoding.
std::map<std::string, std::string> TiedNames;
for (unsigned i = 0; i < CGI.Operands.size(); ++i) {
int tiedTo = CGI.Operands[i].getTiedRegister();
if (tiedTo != -1) {
std::pair<unsigned, unsigned> SO =
CGI.Operands.getSubOperandNumber(tiedTo);
TiedNames[InOutOperands[i].second] = InOutOperands[SO.first].second;
TiedNames[InOutOperands[SO.first].second] = InOutOperands[i].second;
}
}
std::map<std::string, std::vector<OperandInfo>> NumberedInsnOperands;
std::set<std::string> NumberedInsnOperandsNoTie;
if (Target.getInstructionSet()->
getValueAsBit("decodePositionallyEncodedOperands")) {
const std::vector<RecordVal> &Vals = Def.getValues();
unsigned NumberedOp = 0;
std::set<unsigned> NamedOpIndices;
if (Target.getInstructionSet()->
getValueAsBit("noNamedPositionallyEncodedOperands"))
// Collect the set of operand indices that might correspond to named
// operand, and skip these when assigning operands based on position.
for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
unsigned OpIdx;
if (!CGI.Operands.hasOperandNamed(Vals[i].getName(), OpIdx))
continue;
NamedOpIndices.insert(OpIdx);
}
for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
// Ignore fixed fields in the record, we're looking for values like:
// bits<5> RST = { ?, ?, ?, ?, ? };
if (Vals[i].getPrefix() || Vals[i].getValue()->isComplete())
continue;
// Determine if Vals[i] actually contributes to the Inst encoding.
unsigned bi = 0;
for (; bi < Bits.getNumBits(); ++bi) {
VarInit *Var = nullptr;
VarBitInit *BI = dyn_cast<VarBitInit>(Bits.getBit(bi));
if (BI)
Var = dyn_cast<VarInit>(BI->getBitVar());
else
Var = dyn_cast<VarInit>(Bits.getBit(bi));
if (Var && Var->getName() == Vals[i].getName())
break;
}
if (bi == Bits.getNumBits())
continue;
// Skip variables that correspond to explicitly-named operands.
unsigned OpIdx;
if (CGI.Operands.hasOperandNamed(Vals[i].getName(), OpIdx))
continue;
// Get the bit range for this operand:
unsigned bitStart = bi++, bitWidth = 1;
for (; bi < Bits.getNumBits(); ++bi) {
VarInit *Var = nullptr;
VarBitInit *BI = dyn_cast<VarBitInit>(Bits.getBit(bi));
if (BI)
Var = dyn_cast<VarInit>(BI->getBitVar());
else
Var = dyn_cast<VarInit>(Bits.getBit(bi));
if (!Var)
break;
if (Var->getName() != Vals[i].getName())
break;
++bitWidth;
}
unsigned NumberOps = CGI.Operands.size();
while (NumberedOp < NumberOps &&
(CGI.Operands.isFlatOperandNotEmitted(NumberedOp) ||
(!NamedOpIndices.empty() && NamedOpIndices.count(
CGI.Operands.getSubOperandNumber(NumberedOp).first))))
++NumberedOp;
OpIdx = NumberedOp++;
// OpIdx now holds the ordered operand number of Vals[i].
std::pair<unsigned, unsigned> SO =
CGI.Operands.getSubOperandNumber(OpIdx);
const std::string &Name = CGI.Operands[SO.first].Name;
LLVM_DEBUG(dbgs() << "Numbered operand mapping for " << Def.getName()
<< ": " << Name << "(" << SO.first << ", " << SO.second
<< ") => " << Vals[i].getName() << "\n");
std::string Decoder;
Record *TypeRecord = CGI.Operands[SO.first].Rec;
RecordVal *DecoderString = TypeRecord->getValue("DecoderMethod");
StringInit *String = DecoderString ?
dyn_cast<StringInit>(DecoderString->getValue()) : nullptr;
if (String && String->getValue() != "")
Decoder = String->getValue();
if (Decoder == "" &&
CGI.Operands[SO.first].MIOperandInfo &&
CGI.Operands[SO.first].MIOperandInfo->getNumArgs()) {
Init *Arg = CGI.Operands[SO.first].MIOperandInfo->
getArg(SO.second);
if (DefInit *DI = cast<DefInit>(Arg))
TypeRecord = DI->getDef();
}
bool isReg = false;
if (TypeRecord->isSubClassOf("RegisterOperand"))
TypeRecord = TypeRecord->getValueAsDef("RegClass");
if (TypeRecord->isSubClassOf("RegisterClass")) {
Decoder = "Decode" + TypeRecord->getName().str() + "RegisterClass";
isReg = true;
} else if (TypeRecord->isSubClassOf("PointerLikeRegClass")) {
Decoder = "DecodePointerLikeRegClass" +
utostr(TypeRecord->getValueAsInt("RegClassKind"));
isReg = true;
}
DecoderString = TypeRecord->getValue("DecoderMethod");
String = DecoderString ?
dyn_cast<StringInit>(DecoderString->getValue()) : nullptr;
if (!isReg && String && String->getValue() != "")
Decoder = String->getValue();
RecordVal *HasCompleteDecoderVal =
TypeRecord->getValue("hasCompleteDecoder");
BitInit *HasCompleteDecoderBit = HasCompleteDecoderVal ?
dyn_cast<BitInit>(HasCompleteDecoderVal->getValue()) : nullptr;
bool HasCompleteDecoder = HasCompleteDecoderBit ?
HasCompleteDecoderBit->getValue() : true;
OperandInfo OpInfo(Decoder, HasCompleteDecoder);
OpInfo.addField(bitStart, bitWidth, 0);
NumberedInsnOperands[Name].push_back(OpInfo);
// FIXME: For complex operands with custom decoders we can't handle tied
// sub-operands automatically. Skip those here and assume that this is
// fixed up elsewhere.
if (CGI.Operands[SO.first].MIOperandInfo &&
CGI.Operands[SO.first].MIOperandInfo->getNumArgs() > 1 &&
String && String->getValue() != "")
NumberedInsnOperandsNoTie.insert(Name);
}
}
// For each operand, see if we can figure out where it is encoded.
for (const auto &Op : InOutOperands) {
if (!NumberedInsnOperands[Op.second].empty()) {
InsnOperands.insert(InsnOperands.end(),
NumberedInsnOperands[Op.second].begin(),
NumberedInsnOperands[Op.second].end());
continue;
}
if (!NumberedInsnOperands[TiedNames[Op.second]].empty()) {
if (!NumberedInsnOperandsNoTie.count(TiedNames[Op.second])) {
// Figure out to which (sub)operand we're tied.
unsigned i = CGI.Operands.getOperandNamed(TiedNames[Op.second]);
int tiedTo = CGI.Operands[i].getTiedRegister();
if (tiedTo == -1) {
i = CGI.Operands.getOperandNamed(Op.second);
tiedTo = CGI.Operands[i].getTiedRegister();
}
if (tiedTo != -1) {
std::pair<unsigned, unsigned> SO =
CGI.Operands.getSubOperandNumber(tiedTo);
InsnOperands.push_back(NumberedInsnOperands[TiedNames[Op.second]]
[SO.second]);
}
}
continue;
}
TypedInit *TI = cast<TypedInit>(Op.first);
// At this point, we can locate the decoder field, but we need to know how
// to interpret it. As a first step, require the target to provide
// callbacks for decoding register classes.
std::string Decoder = findOperandDecoderMethod(TI);
Record *TypeRecord = cast<DefInit>(TI)->getDef();
RecordVal *HasCompleteDecoderVal =
TypeRecord->getValue("hasCompleteDecoder");
BitInit *HasCompleteDecoderBit = HasCompleteDecoderVal ?
dyn_cast<BitInit>(HasCompleteDecoderVal->getValue()) : nullptr;
bool HasCompleteDecoder = HasCompleteDecoderBit ?
HasCompleteDecoderBit->getValue() : true;
OperandInfo OpInfo(Decoder, HasCompleteDecoder);
unsigned Base = ~0U;
unsigned Width = 0;
unsigned Offset = 0;
for (unsigned bi = 0; bi < Bits.getNumBits(); ++bi) {
VarInit *Var = nullptr;
VarBitInit *BI = dyn_cast<VarBitInit>(Bits.getBit(bi));
if (BI)
Var = dyn_cast<VarInit>(BI->getBitVar());
else
Var = dyn_cast<VarInit>(Bits.getBit(bi));
if (!Var) {
if (Base != ~0U) {
OpInfo.addField(Base, Width, Offset);
Base = ~0U;
Width = 0;
Offset = 0;
}
continue;
}
if (Var->getName() != Op.second &&
Var->getName() != TiedNames[Op.second]) {
if (Base != ~0U) {
OpInfo.addField(Base, Width, Offset);
Base = ~0U;
Width = 0;
Offset = 0;
}
continue;
}
if (Base == ~0U) {
Base = bi;
Width = 1;
Offset = BI ? BI->getBitNum() : 0;
} else if (BI && BI->getBitNum() != Offset + Width) {
OpInfo.addField(Base, Width, Offset);
Base = bi;
Width = 1;
Offset = BI->getBitNum();
} else {
++Width;
}
}
if (Base != ~0U)
OpInfo.addField(Base, Width, Offset);
if (OpInfo.numFields() > 0)
InsnOperands.push_back(OpInfo);
}
Operands[Opc] = InsnOperands;
#if 0
LLVM_DEBUG({
// Dumps the instruction encoding bits.
dumpBits(errs(), Bits);
errs() << '\n';
// Dumps the list of operand info.
for (unsigned i = 0, e = CGI.Operands.size(); i != e; ++i) {
const CGIOperandList::OperandInfo &Info = CGI.Operands[i];
const std::string &OperandName = Info.Name;
const Record &OperandDef = *Info.Rec;
errs() << "\t" << OperandName << " (" << OperandDef.getName() << ")\n";
}
});
#endif
return true;
}
// emitFieldFromInstruction - Emit the templated helper function
// fieldFromInstruction().
// On Windows we make sure that this function is not inlined when
// using the VS compiler. It has a bug which causes the function
// to be optimized out in some circustances. See llvm.org/pr38292
static void emitFieldFromInstruction(formatted_raw_ostream &OS) {
OS << "// Helper functions for extracting fields from encoded instructions.\n"
<< "// InsnType must either be integral or an APInt-like object that "
"must:\n"
<< "// * Have a static const max_size_in_bits equal to the number of bits "
"in the\n"
<< "// encoding.\n"
<< "// * be default-constructible and copy-constructible\n"
<< "// * be constructible from a uint64_t\n"
<< "// * be constructible from an APInt (this can be private)\n"
<< "// * Support getBitsSet(loBit, hiBit)\n"
<< "// * be convertible to uint64_t\n"
<< "// * Support the ~, &, ==, !=, and |= operators with other objects of "
"the same type\n"
<< "// * Support shift (<<, >>) with signed and unsigned integers on the "
"RHS\n"
<< "// * Support put (<<) to raw_ostream&\n"
<< "template<typename InsnType>\n"
<< "#if defined(_MSC_VER) && !defined(__clang__)\n"
<< "__declspec(noinline)\n"
<< "#endif\n"
<< "static InsnType fieldFromInstruction(InsnType insn, unsigned "
"startBit,\n"
<< " unsigned numBits, "
"std::true_type) {\n"
<< " assert(startBit + numBits <= 64 && \"Cannot support >64-bit "
"extractions!\");\n"
<< " assert(startBit + numBits <= (sizeof(InsnType) * 8) &&\n"
<< " \"Instruction field out of bounds!\");\n"
<< " InsnType fieldMask;\n"
<< " if (numBits == sizeof(InsnType) * 8)\n"
<< " fieldMask = (InsnType)(-1LL);\n"
<< " else\n"
<< " fieldMask = (((InsnType)1 << numBits) - 1) << startBit;\n"
<< " return (insn & fieldMask) >> startBit;\n"
<< "}\n"
<< "\n"
<< "template<typename InsnType>\n"
<< "static InsnType fieldFromInstruction(InsnType insn, unsigned "
"startBit,\n"
<< " unsigned numBits, "
"std::false_type) {\n"
<< " assert(startBit + numBits <= InsnType::max_size_in_bits && "
"\"Instruction field out of bounds!\");\n"
<< " InsnType fieldMask = InsnType::getBitsSet(0, numBits);\n"
<< " return (insn >> startBit) & fieldMask;\n"
<< "}\n"
<< "\n"
<< "template<typename InsnType>\n"
<< "static InsnType fieldFromInstruction(InsnType insn, unsigned "
"startBit,\n"
<< " unsigned numBits) {\n"
<< " return fieldFromInstruction(insn, startBit, numBits, "
"std::is_integral<InsnType>());\n"
<< "}\n\n";
}
// emitDecodeInstruction - Emit the templated helper function
// decodeInstruction().
static void emitDecodeInstruction(formatted_raw_ostream &OS) {
OS << "template<typename InsnType>\n"
<< "static DecodeStatus decodeInstruction(const uint8_t DecodeTable[], "
"MCInst &MI,\n"
<< " InsnType insn, uint64_t "
"Address,\n"
<< " const void *DisAsm,\n"
<< " const MCSubtargetInfo &STI) {\n"
<< " const FeatureBitset& Bits = STI.getFeatureBits();\n"
<< "\n"
<< " const uint8_t *Ptr = DecodeTable;\n"
<< " uint32_t CurFieldValue = 0;\n"
<< " DecodeStatus S = MCDisassembler::Success;\n"
<< " while (true) {\n"
<< " ptrdiff_t Loc = Ptr - DecodeTable;\n"
<< " switch (*Ptr) {\n"
<< " default:\n"
<< " errs() << Loc << \": Unexpected decode table opcode!\\n\";\n"
<< " return MCDisassembler::Fail;\n"
<< " case MCD::OPC_ExtractField: {\n"
<< " unsigned Start = *++Ptr;\n"
<< " unsigned Len = *++Ptr;\n"
<< " ++Ptr;\n"
<< " CurFieldValue = fieldFromInstruction(insn, Start, Len);\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_ExtractField(\" << Start << "
"\", \"\n"
<< " << Len << \"): \" << CurFieldValue << \"\\n\");\n"
<< " break;\n"
<< " }\n"
<< " case MCD::OPC_FilterValue: {\n"
<< " // Decode the field value.\n"
<< " unsigned Len;\n"
<< " InsnType Val = decodeULEB128(++Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " // NumToSkip is a plain 24-bit integer.\n"
<< " unsigned NumToSkip = *Ptr++;\n"
<< " NumToSkip |= (*Ptr++) << 8;\n"
<< " NumToSkip |= (*Ptr++) << 16;\n"
<< "\n"
<< " // Perform the filter operation.\n"
<< " if (Val != CurFieldValue)\n"
<< " Ptr += NumToSkip;\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_FilterValue(\" << Val << "
"\", \" << NumToSkip\n"
<< " << \"): \" << ((Val != CurFieldValue) ? \"FAIL:\" "
": \"PASS:\")\n"
<< " << \" continuing at \" << (Ptr - DecodeTable) << "
"\"\\n\");\n"
<< "\n"
<< " break;\n"
<< " }\n"
<< " case MCD::OPC_CheckField: {\n"
<< " unsigned Start = *++Ptr;\n"
<< " unsigned Len = *++Ptr;\n"
<< " InsnType FieldValue = fieldFromInstruction(insn, Start, Len);\n"
<< " // Decode the field value.\n"
<< " uint32_t ExpectedValue = decodeULEB128(++Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " // NumToSkip is a plain 24-bit integer.\n"
<< " unsigned NumToSkip = *Ptr++;\n"
<< " NumToSkip |= (*Ptr++) << 8;\n"
<< " NumToSkip |= (*Ptr++) << 16;\n"
<< "\n"
<< " // If the actual and expected values don't match, skip.\n"
<< " if (ExpectedValue != FieldValue)\n"
<< " Ptr += NumToSkip;\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_CheckField(\" << Start << "
"\", \"\n"
<< " << Len << \", \" << ExpectedValue << \", \" << "
"NumToSkip\n"
<< " << \"): FieldValue = \" << FieldValue << \", "
"ExpectedValue = \"\n"
<< " << ExpectedValue << \": \"\n"
<< " << ((ExpectedValue == FieldValue) ? \"PASS\\n\" : "
"\"FAIL\\n\"));\n"
<< " break;\n"
<< " }\n"
<< " case MCD::OPC_CheckPredicate: {\n"
<< " unsigned Len;\n"
<< " // Decode the Predicate Index value.\n"
<< " unsigned PIdx = decodeULEB128(++Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " // NumToSkip is a plain 24-bit integer.\n"
<< " unsigned NumToSkip = *Ptr++;\n"
<< " NumToSkip |= (*Ptr++) << 8;\n"
<< " NumToSkip |= (*Ptr++) << 16;\n"
<< " // Check the predicate.\n"
<< " bool Pred;\n"
<< " if (!(Pred = checkDecoderPredicate(PIdx, Bits)))\n"
<< " Ptr += NumToSkip;\n"
<< " (void)Pred;\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_CheckPredicate(\" << PIdx "
"<< \"): \"\n"
<< " << (Pred ? \"PASS\\n\" : \"FAIL\\n\"));\n"
<< "\n"
<< " break;\n"
<< " }\n"
<< " case MCD::OPC_Decode: {\n"
<< " unsigned Len;\n"
<< " // Decode the Opcode value.\n"
<< " unsigned Opc = decodeULEB128(++Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " unsigned DecodeIdx = decodeULEB128(Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< "\n"
<< " MI.clear();\n"
<< " MI.setOpcode(Opc);\n"
<< " bool DecodeComplete;\n"
<< " S = decodeToMCInst(S, DecodeIdx, insn, MI, Address, DisAsm, "
"DecodeComplete);\n"
<< " assert(DecodeComplete);\n"
<< "\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_Decode: opcode \" << Opc\n"
<< " << \", using decoder \" << DecodeIdx << \": \"\n"
<< " << (S != MCDisassembler::Fail ? \"PASS\" : "
"\"FAIL\") << \"\\n\");\n"
<< " return S;\n"
<< " }\n"
<< " case MCD::OPC_TryDecode: {\n"
<< " unsigned Len;\n"
<< " // Decode the Opcode value.\n"
<< " unsigned Opc = decodeULEB128(++Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " unsigned DecodeIdx = decodeULEB128(Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " // NumToSkip is a plain 24-bit integer.\n"
<< " unsigned NumToSkip = *Ptr++;\n"
<< " NumToSkip |= (*Ptr++) << 8;\n"
<< " NumToSkip |= (*Ptr++) << 16;\n"
<< "\n"
<< " // Perform the decode operation.\n"
<< " MCInst TmpMI;\n"
<< " TmpMI.setOpcode(Opc);\n"
<< " bool DecodeComplete;\n"
<< " S = decodeToMCInst(S, DecodeIdx, insn, TmpMI, Address, DisAsm, "
"DecodeComplete);\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_TryDecode: opcode \" << "
"Opc\n"
<< " << \", using decoder \" << DecodeIdx << \": \");\n"
<< "\n"
<< " if (DecodeComplete) {\n"
<< " // Decoding complete.\n"
<< " LLVM_DEBUG(dbgs() << (S != MCDisassembler::Fail ? \"PASS\" : "
"\"FAIL\") << \"\\n\");\n"
<< " MI = TmpMI;\n"
<< " return S;\n"
<< " } else {\n"
<< " assert(S == MCDisassembler::Fail);\n"
<< " // If the decoding was incomplete, skip.\n"
<< " Ptr += NumToSkip;\n"
<< " LLVM_DEBUG(dbgs() << \"FAIL: continuing at \" << (Ptr - "
"DecodeTable) << \"\\n\");\n"
<< " // Reset decode status. This also drops a SoftFail status "
"that could be\n"
<< " // set before the decode attempt.\n"
<< " S = MCDisassembler::Success;\n"
<< " }\n"
<< " break;\n"
<< " }\n"
<< " case MCD::OPC_SoftFail: {\n"
<< " // Decode the mask values.\n"
<< " unsigned Len;\n"
<< " InsnType PositiveMask = decodeULEB128(++Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " InsnType NegativeMask = decodeULEB128(Ptr, &Len);\n"
<< " Ptr += Len;\n"
<< " bool Fail = (insn & PositiveMask) || (~insn & NegativeMask);\n"
<< " if (Fail)\n"
<< " S = MCDisassembler::SoftFail;\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_SoftFail: \" << (Fail ? "
"\"FAIL\\n\":\"PASS\\n\"));\n"
<< " break;\n"
<< " }\n"
<< " case MCD::OPC_Fail: {\n"
<< " LLVM_DEBUG(dbgs() << Loc << \": OPC_Fail\\n\");\n"
<< " return MCDisassembler::Fail;\n"
<< " }\n"
<< " }\n"
<< " }\n"
<< " llvm_unreachable(\"bogosity detected in disassembler state "
"machine!\");\n"
<< "}\n\n";
}
// Emits disassembler code for instruction decoding.
void FixedLenDecoderEmitter::run(raw_ostream &o) {
formatted_raw_ostream OS(o);
OS << "#include \"llvm/MC/MCInst.h\"\n";
OS << "#include \"llvm/Support/Debug.h\"\n";
OS << "#include \"llvm/Support/DataTypes.h\"\n";
OS << "#include \"llvm/Support/LEB128.h\"\n";
OS << "#include \"llvm/Support/raw_ostream.h\"\n";
OS << "#include <assert.h>\n";
OS << '\n';
OS << "namespace llvm {\n\n";
emitFieldFromInstruction(OS);
Target.reverseBitsForLittleEndianEncoding();
// Parameterize the decoders based on namespace and instruction width.
const auto &NumberedInstructions = Target.getInstructionsByEnumValue();
NumberedEncodings.reserve(NumberedInstructions.size());
for (const auto &NumberedInstruction : NumberedInstructions)
NumberedEncodings.emplace_back(NumberedInstruction->TheDef, NumberedInstruction);
std::map<std::pair<std::string, unsigned>,
std::vector<unsigned>> OpcMap;
std::map<unsigned, std::vector<OperandInfo>> Operands;
for (unsigned i = 0; i < NumberedEncodings.size(); ++i) {
const CodeGenInstruction *Inst = NumberedEncodings[i].Inst;
const Record *Def = Inst->TheDef;
unsigned Size = Def->getValueAsInt("Size");
if (Def->getValueAsString("Namespace") == "TargetOpcode" ||
Def->getValueAsBit("isPseudo") ||
Def->getValueAsBit("isAsmParserOnly") ||
Def->getValueAsBit("isCodeGenOnly"))
continue;
StringRef DecoderNamespace = Def->getValueAsString("DecoderNamespace");
if (Size) {
if (populateInstruction(Target, *Inst, i, Operands)) {
OpcMap[std::make_pair(DecoderNamespace, Size)].push_back(i);
}
}
}
DecoderTableInfo TableInfo;
for (const auto &Opc : OpcMap) {
// Emit the decoder for this namespace+width combination.
ArrayRef<EncodingAndInst> NumberedEncodingsRef(NumberedEncodings.data(),
NumberedEncodings.size());
FilterChooser FC(NumberedEncodingsRef, Opc.second, Operands,
8 * Opc.first.second, this);
// The decode table is cleared for each top level decoder function. The
// predicates and decoders themselves, however, are shared across all
// decoders to give more opportunities for uniqueing.
TableInfo.Table.clear();
TableInfo.FixupStack.clear();
TableInfo.Table.reserve(16384);
TableInfo.FixupStack.emplace_back();
FC.emitTableEntries(TableInfo);
// Any NumToSkip fixups in the top level scope can resolve to the
// OPC_Fail at the end of the table.
assert(TableInfo.FixupStack.size() == 1 && "fixup stack phasing error!");
// Resolve any NumToSkip fixups in the current scope.
resolveTableFixups(TableInfo.Table, TableInfo.FixupStack.back(),
TableInfo.Table.size());
TableInfo.FixupStack.clear();
TableInfo.Table.push_back(MCD::OPC_Fail);
// Print the table to the output stream.
emitTable(OS, TableInfo.Table, 0, FC.getBitWidth(), Opc.first.first);
OS.flush();
}
// Emit the predicate function.
emitPredicateFunction(OS, TableInfo.Predicates, 0);
// Emit the decoder function.
emitDecoderFunction(OS, TableInfo.Decoders, 0);
// Emit the main entry point for the decoder, decodeInstruction().
emitDecodeInstruction(OS);
OS << "\n} // End llvm namespace\n";
}
namespace llvm {
void EmitFixedLenDecoder(RecordKeeper &RK, raw_ostream &OS,
const std::string &PredicateNamespace,
const std::string &GPrefix,
const std::string &GPostfix, const std::string &ROK,
const std::string &RFail, const std::string &L) {
FixedLenDecoderEmitter(RK, PredicateNamespace, GPrefix, GPostfix,
ROK, RFail, L).run(OS);
}
} // end namespace llvm
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