CompressInstEmitter.cpp | Explore in Territory

//===-------- CompressInstEmitter.cpp - Generator for Compression ---------===//
//
// 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
//
// CompressInstEmitter implements a tablegen-driven CompressPat based
// Instruction Compression mechanism.
//
//===----------------------------------------------------------------------===//
//
// CompressInstEmitter implements a tablegen-driven CompressPat Instruction
// Compression mechanism for generating compressed instructions from the
// expanded instruction form.

// This tablegen backend processes CompressPat declarations in a
// td file and generates all the required checks to validate the pattern
// declarations; validate the input and output operands to generate the correct
// compressed instructions. The checks include validating different types of
// operands; register operands, immediate operands, fixed register and fixed
// immediate inputs.
//
// Example:
// /// Defines a Pat match between compressed and uncompressed instruction.
// /// The relationship and helper function generation are handled by
// /// CompressInstEmitter backend.
// class CompressPat<dag input, dag output, list<Predicate> predicates = []> {
//   /// Uncompressed instruction description.
//   dag Input = input;
//   /// Compressed instruction description.
//   dag Output = output;
//   /// Predicates that must be true for this to match.
//   list<Predicate> Predicates = predicates;
//   /// Duplicate match when tied operand is just different.
//   bit isCompressOnly = false;
// }
//
// let Predicates = [HasStdExtC] in {
// def : CompressPat<(ADD GPRNoX0:$rs1, GPRNoX0:$rs1, GPRNoX0:$rs2),
//                   (C_ADD GPRNoX0:$rs1, GPRNoX0:$rs2)>;
// }
//
// The <TargetName>GenCompressInstEmitter.inc is an auto-generated header
// file which exports two functions for compressing/uncompressing MCInst
// instructions, plus some helper functions:
//
// bool compressInst(MCInst &OutInst, const MCInst &MI,
//                   const MCSubtargetInfo &STI);
//
// bool uncompressInst(MCInst &OutInst, const MCInst &MI,
//                     const MCSubtargetInfo &STI);
//
// In addition, it exports a function for checking whether
// an instruction is compressable:
//
// bool isCompressibleInst(const MachineInstr& MI,
//                         const <TargetName>Subtarget &STI);
//
// The clients that include this auto-generated header file and
// invoke these functions can compress an instruction before emitting
// it in the target-specific ASM or ELF streamer or can uncompress
// an instruction before printing it when the expanded instruction
// format aliases is favored.

//===----------------------------------------------------------------------===//

#include "Common/CodeGenInstruction.h"
#include "Common/CodeGenRegisters.h"
#include "Common/CodeGenTarget.h"
#include "llvm/ADT/IndexedMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/TableGen/Error.h"
#include "llvm/TableGen/Record.h"
#include "llvm/TableGen/TableGenBackend.h"
#include <set>
#include <vector>
usingnamespacellvm;

#define DEBUG_TYPE …

namespace {
class CompressInstEmitter { … };
} // End anonymous namespace.

bool CompressInstEmitter::validateRegister(const Record *Reg,
                                           const Record *RegClass) { … }

bool CompressInstEmitter::validateTypes(const Record *DagOpType,
                                        const Record *InstOpType,
                                        bool IsSourceInst) { … }

/// The patterns in the Dag contain different types of operands:
/// Register operands, e.g.: GPRC:$rs1; Fixed registers, e.g: X1; Immediate
/// operands, e.g.: simm6:$imm; Fixed immediate operands, e.g.: 0. This function
/// maps Dag operands to its corresponding instruction operands. For register
/// operands and fixed registers it expects the Dag operand type to be contained
/// in the instantiated instruction operand type. For immediate operands and
/// immediates no validation checks are enforced at pattern validation time.
void CompressInstEmitter::addDagOperandMapping(Record *Rec, DagInit *Dag,
                                               CodeGenInstruction &Inst,
                                               IndexedMap<OpData> &OperandMap,
                                               bool IsSourceInst) { … }

// Verify the Dag operand count is enough to build an instruction.
static bool verifyDagOpCount(CodeGenInstruction &Inst, DagInit *Dag,
                             bool IsSource) { … }

static bool validateArgsTypes(Init *Arg1, Init *Arg2) { … }

// Creates a mapping between the operand name in the Dag (e.g. $rs1) and
// its index in the list of Dag operands and checks that operands with the same
// name have the same types. For example in 'C_ADD $rs1, $rs2' we generate the
// mapping $rs1 --> 0, $rs2 ---> 1. If the operand appears twice in the (tied)
// same Dag we use the last occurrence for indexing.
void CompressInstEmitter::createDagOperandMapping(
    Record *Rec, StringMap<unsigned> &SourceOperands,
    StringMap<unsigned> &DestOperands, DagInit *SourceDag, DagInit *DestDag,
    IndexedMap<OpData> &SourceOperandMap) { … }

/// Map operand names in the Dag to their index in both corresponding input and
/// output instructions. Validate that operands defined in the input are
/// used in the output pattern while populating the maps.
void CompressInstEmitter::createInstOperandMapping(
    Record *Rec, DagInit *SourceDag, DagInit *DestDag,
    IndexedMap<OpData> &SourceOperandMap, IndexedMap<OpData> &DestOperandMap,
    StringMap<unsigned> &SourceOperands, CodeGenInstruction &DestInst) { … }

/// Validates the CompressPattern and create operand mapping.
/// These are the checks to validate a CompressPat pattern declarations.
/// Error out with message under these conditions:
/// - Dag Input opcode is an expanded instruction and Dag Output opcode is a
///   compressed instruction.
/// - Operands in Dag Input must be all used in Dag Output.
///   Register Operand type in Dag Input Type must be contained in the
///   corresponding Source Instruction type.
/// - Register Operand type in Dag Input must be the same as in Dag Ouput.
/// - Register Operand type in Dag Output must be the same as the
///   corresponding Destination Inst type.
/// - Immediate Operand type in Dag Input must be the same as in Dag Ouput.
/// - Immediate Operand type in Dag Ouput must be the same as the corresponding
///   Destination Instruction type.
/// - Fixed register must be contained in the corresponding Source Instruction
///   type.
/// - Fixed register must be contained in the corresponding Destination
///   Instruction type.
/// Warning message printed under these conditions:
/// - Fixed immediate in Dag Input or Dag Ouput cannot be checked at this time
///   and generate warning.
/// - Immediate operand type in Dag Input differs from the corresponding Source
///   Instruction type and generate a warning.
void CompressInstEmitter::evaluateCompressPat(Record *Rec) { … }

static void
getReqFeatures(std::set<std::pair<bool, StringRef>> &FeaturesSet,
               std::set<std::set<std::pair<bool, StringRef>>> &AnyOfFeatureSets,
               const std::vector<Record *> &ReqFeatures) { … }

static unsigned getPredicates(DenseMap<const Record *, unsigned> &PredicateMap,
                              std::vector<const Record *> &Predicates,
                              const Record *Rec, StringRef Name) { … }

static void printPredicates(const std::vector<const Record *> &Predicates,
                            StringRef Name, raw_ostream &OS) { … }

static void mergeCondAndCode(raw_ostream &CombinedStream, StringRef CondStr,
                             StringRef CodeStr) { … }

void CompressInstEmitter::emitCompressInstEmitter(raw_ostream &OS,
                                                  EmitterType EType) { … }

void CompressInstEmitter::run(raw_ostream &OS) { … }

static TableGen::Emitter::OptClass<CompressInstEmitter>
    X("gen-compress-inst-emitter", "Generate compressed instructions.");
llvm/llvm/utils/TableGen/CompressInstEmitter.cpp
