llvm-project/llvm/utils/TableGen/VarLenCodeEmitterGen.cpp
2023-02-17 00:32:46 +09:00

515 lines
18 KiB
C++

//===- VarLenCodeEmitterGen.cpp - CEG for variable-length insts -----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// The CodeEmitterGen component for variable-length instructions.
//
// The basic CodeEmitterGen is almost exclusively designed for fixed-
// length instructions. A good analogy for its encoding scheme is how printf
// works: The (immutable) formatting string represent the fixed values in the
// encoded instruction. Placeholders (i.e. %something), on the other hand,
// represent encoding for instruction operands.
// ```
// printf("1101 %src 1001 %dst", <encoded value for operand `src`>,
// <encoded value for operand `dst`>);
// ```
// VarLenCodeEmitterGen in this file provides an alternative encoding scheme
// that works more like a C++ stream operator:
// ```
// OS << 0b1101;
// if (Cond)
// OS << OperandEncoding0;
// OS << 0b1001 << OperandEncoding1;
// ```
// You are free to concatenate arbitrary types (and sizes) of encoding
// fragments on any bit position, bringing more flexibilities on defining
// encoding for variable-length instructions.
//
// In a more specific way, instruction encoding is represented by a DAG type
// `Inst` field. Here is an example:
// ```
// dag Inst = (descend 0b1101, (operand "$src", 4), 0b1001,
// (operand "$dst", 4));
// ```
// It represents the following instruction encoding:
// ```
// MSB LSB
// 1101<encoding for operand src>1001<encoding for operand dst>
// ```
// For more details about DAG operators in the above snippet, please
// refer to \file include/llvm/Target/Target.td.
//
// VarLenCodeEmitter will convert the above DAG into the same helper function
// generated by CodeEmitter, `MCCodeEmitter::getBinaryCodeForInstr` (except
// for few details).
//
//===----------------------------------------------------------------------===//
#include "VarLenCodeEmitterGen.h"
#include "CodeGenHwModes.h"
#include "CodeGenInstruction.h"
#include "CodeGenTarget.h"
#include "InfoByHwMode.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TableGen/Error.h"
#include "llvm/TableGen/Record.h"
using namespace llvm;
namespace {
class VarLenCodeEmitterGen {
RecordKeeper &Records;
DenseMap<Record *, VarLenInst> VarLenInsts;
// Emit based values (i.e. fixed bits in the encoded instructions)
void emitInstructionBaseValues(
raw_ostream &OS,
ArrayRef<const CodeGenInstruction *> NumberedInstructions,
CodeGenTarget &Target, int HwMode = -1);
std::string getInstructionCase(Record *R, CodeGenTarget &Target);
std::string getInstructionCaseForEncoding(Record *R, Record *EncodingDef,
CodeGenTarget &Target);
public:
explicit VarLenCodeEmitterGen(RecordKeeper &R) : Records(R) {}
void run(raw_ostream &OS);
};
} // end anonymous namespace
// Get the name of custom encoder or decoder, if there is any.
// Returns `{encoder name, decoder name}`.
static std::pair<StringRef, StringRef> getCustomCoders(ArrayRef<Init *> Args) {
std::pair<StringRef, StringRef> Result;
for (const auto *Arg : Args) {
const auto *DI = dyn_cast<DagInit>(Arg);
if (!DI)
continue;
const Init *Op = DI->getOperator();
if (!isa<DefInit>(Op))
continue;
// syntax: `(<encoder | decoder> "function name")`
StringRef OpName = cast<DefInit>(Op)->getDef()->getName();
if (OpName != "encoder" && OpName != "decoder")
continue;
if (!DI->getNumArgs() || !isa<StringInit>(DI->getArg(0)))
PrintFatalError("expected '" + OpName +
"' directive to be followed by a custom function name.");
StringRef FuncName = cast<StringInit>(DI->getArg(0))->getValue();
if (OpName == "encoder")
Result.first = FuncName;
else
Result.second = FuncName;
}
return Result;
}
VarLenInst::VarLenInst(const DagInit *DI, const RecordVal *TheDef)
: TheDef(TheDef), NumBits(0U) {
buildRec(DI);
for (const auto &S : Segments)
NumBits += S.BitWidth;
}
void VarLenInst::buildRec(const DagInit *DI) {
assert(TheDef && "The def record is nullptr ?");
std::string Op = DI->getOperator()->getAsString();
if (Op == "ascend" || Op == "descend") {
bool Reverse = Op == "descend";
int i = Reverse ? DI->getNumArgs() - 1 : 0;
int e = Reverse ? -1 : DI->getNumArgs();
int s = Reverse ? -1 : 1;
for (; i != e; i += s) {
const Init *Arg = DI->getArg(i);
if (const auto *BI = dyn_cast<BitsInit>(Arg)) {
if (!BI->isComplete())
PrintFatalError(TheDef->getLoc(),
"Expecting complete bits init in `" + Op + "`");
Segments.push_back({BI->getNumBits(), BI});
} else if (const auto *BI = dyn_cast<BitInit>(Arg)) {
if (!BI->isConcrete())
PrintFatalError(TheDef->getLoc(),
"Expecting concrete bit init in `" + Op + "`");
Segments.push_back({1, BI});
} else if (const auto *SubDI = dyn_cast<DagInit>(Arg)) {
buildRec(SubDI);
} else {
PrintFatalError(TheDef->getLoc(), "Unrecognized type of argument in `" +
Op + "`: " + Arg->getAsString());
}
}
} else if (Op == "operand") {
// (operand <operand name>, <# of bits>,
// [(encoder <custom encoder>)][, (decoder <custom decoder>)])
if (DI->getNumArgs() < 2)
PrintFatalError(TheDef->getLoc(),
"Expecting at least 2 arguments for `operand`");
HasDynamicSegment = true;
const Init *OperandName = DI->getArg(0), *NumBits = DI->getArg(1);
if (!isa<StringInit>(OperandName) || !isa<IntInit>(NumBits))
PrintFatalError(TheDef->getLoc(), "Invalid argument types for `operand`");
auto NumBitsVal = cast<IntInit>(NumBits)->getValue();
if (NumBitsVal <= 0)
PrintFatalError(TheDef->getLoc(), "Invalid number of bits for `operand`");
auto [CustomEncoder, CustomDecoder] =
getCustomCoders(DI->getArgs().slice(2));
Segments.push_back({static_cast<unsigned>(NumBitsVal), OperandName,
CustomEncoder, CustomDecoder});
} else if (Op == "slice") {
// (slice <operand name>, <high / low bit>, <low / high bit>,
// [(encoder <custom encoder>)][, (decoder <custom decoder>)])
if (DI->getNumArgs() < 3)
PrintFatalError(TheDef->getLoc(),
"Expecting at least 3 arguments for `slice`");
HasDynamicSegment = true;
Init *OperandName = DI->getArg(0), *HiBit = DI->getArg(1),
*LoBit = DI->getArg(2);
if (!isa<StringInit>(OperandName) || !isa<IntInit>(HiBit) ||
!isa<IntInit>(LoBit))
PrintFatalError(TheDef->getLoc(), "Invalid argument types for `slice`");
auto HiBitVal = cast<IntInit>(HiBit)->getValue(),
LoBitVal = cast<IntInit>(LoBit)->getValue();
if (HiBitVal < 0 || LoBitVal < 0)
PrintFatalError(TheDef->getLoc(), "Invalid bit range for `slice`");
bool NeedSwap = false;
unsigned NumBits = 0U;
if (HiBitVal < LoBitVal) {
NeedSwap = true;
NumBits = static_cast<unsigned>(LoBitVal - HiBitVal + 1);
} else {
NumBits = static_cast<unsigned>(HiBitVal - LoBitVal + 1);
}
auto [CustomEncoder, CustomDecoder] =
getCustomCoders(DI->getArgs().slice(3));
if (NeedSwap) {
// Normalization: Hi bit should always be the second argument.
Init *const NewArgs[] = {OperandName, LoBit, HiBit};
Segments.push_back({NumBits,
DagInit::get(DI->getOperator(), nullptr, NewArgs, {}),
CustomEncoder, CustomDecoder});
} else {
Segments.push_back({NumBits, DI, CustomEncoder, CustomDecoder});
}
}
}
void VarLenCodeEmitterGen::run(raw_ostream &OS) {
CodeGenTarget Target(Records);
auto Insts = Records.getAllDerivedDefinitions("Instruction");
auto NumberedInstructions = Target.getInstructionsByEnumValue();
const CodeGenHwModes &HWM = Target.getHwModes();
// The set of HwModes used by instruction encodings.
std::set<unsigned> HwModes;
for (const CodeGenInstruction *CGI : NumberedInstructions) {
Record *R = CGI->TheDef;
// Create the corresponding VarLenInst instance.
if (R->getValueAsString("Namespace") == "TargetOpcode" ||
R->getValueAsBit("isPseudo"))
continue;
if (const RecordVal *RV = R->getValue("EncodingInfos")) {
if (auto *DI = dyn_cast_or_null<DefInit>(RV->getValue())) {
EncodingInfoByHwMode EBM(DI->getDef(), HWM);
for (auto &KV : EBM) {
HwModes.insert(KV.first);
Record *EncodingDef = KV.second;
RecordVal *RV = EncodingDef->getValue("Inst");
DagInit *DI = cast<DagInit>(RV->getValue());
VarLenInsts.insert({EncodingDef, VarLenInst(DI, RV)});
}
continue;
}
}
RecordVal *RV = R->getValue("Inst");
DagInit *DI = cast<DagInit>(RV->getValue());
VarLenInsts.insert({R, VarLenInst(DI, RV)});
}
// Emit function declaration
OS << "void " << Target.getName()
<< "MCCodeEmitter::getBinaryCodeForInstr(const MCInst &MI,\n"
<< " SmallVectorImpl<MCFixup> &Fixups,\n"
<< " APInt &Inst,\n"
<< " APInt &Scratch,\n"
<< " const MCSubtargetInfo &STI) const {\n";
// Emit instruction base values
if (HwModes.empty()) {
emitInstructionBaseValues(OS, NumberedInstructions, Target);
} else {
for (unsigned HwMode : HwModes)
emitInstructionBaseValues(OS, NumberedInstructions, Target, (int)HwMode);
}
if (!HwModes.empty()) {
OS << " const unsigned **Index;\n";
OS << " const uint64_t *InstBits;\n";
OS << " unsigned HwMode = STI.getHwMode();\n";
OS << " switch (HwMode) {\n";
OS << " default: llvm_unreachable(\"Unknown hardware mode!\"); break;\n";
for (unsigned I : HwModes) {
OS << " case " << I << ": InstBits = InstBits_" << HWM.getMode(I).Name
<< "; Index = Index_" << HWM.getMode(I).Name << "; break;\n";
}
OS << " };\n";
}
// Emit helper function to retrieve base values.
OS << " auto getInstBits = [&](unsigned Opcode) -> APInt {\n"
<< " unsigned NumBits = Index[Opcode][0];\n"
<< " if (!NumBits)\n"
<< " return APInt::getZeroWidth();\n"
<< " unsigned Idx = Index[Opcode][1];\n"
<< " ArrayRef<uint64_t> Data(&InstBits[Idx], "
<< "APInt::getNumWords(NumBits));\n"
<< " return APInt(NumBits, Data);\n"
<< " };\n";
// Map to accumulate all the cases.
std::map<std::string, std::vector<std::string>> CaseMap;
// Construct all cases statement for each opcode
for (Record *R : Insts) {
if (R->getValueAsString("Namespace") == "TargetOpcode" ||
R->getValueAsBit("isPseudo"))
continue;
std::string InstName =
(R->getValueAsString("Namespace") + "::" + R->getName()).str();
std::string Case = getInstructionCase(R, Target);
CaseMap[Case].push_back(std::move(InstName));
}
// Emit initial function code
OS << " const unsigned opcode = MI.getOpcode();\n"
<< " switch (opcode) {\n";
// Emit each case statement
for (const auto &C : CaseMap) {
const std::string &Case = C.first;
const auto &InstList = C.second;
ListSeparator LS("\n");
for (const auto &InstName : InstList)
OS << LS << " case " << InstName << ":";
OS << " {\n";
OS << Case;
OS << " break;\n"
<< " }\n";
}
// Default case: unhandled opcode
OS << " default:\n"
<< " std::string msg;\n"
<< " raw_string_ostream Msg(msg);\n"
<< " Msg << \"Not supported instr: \" << MI;\n"
<< " report_fatal_error(Msg.str().c_str());\n"
<< " }\n";
OS << "}\n\n";
}
static void emitInstBits(raw_ostream &IS, raw_ostream &SS, const APInt &Bits,
unsigned &Index) {
if (!Bits.getNumWords()) {
IS.indent(4) << "{/*NumBits*/0, /*Index*/0},";
return;
}
IS.indent(4) << "{/*NumBits*/" << Bits.getBitWidth() << ", "
<< "/*Index*/" << Index << "},";
SS.indent(4);
for (unsigned I = 0; I < Bits.getNumWords(); ++I, ++Index)
SS << "UINT64_C(" << utostr(Bits.getRawData()[I]) << "),";
}
void VarLenCodeEmitterGen::emitInstructionBaseValues(
raw_ostream &OS, ArrayRef<const CodeGenInstruction *> NumberedInstructions,
CodeGenTarget &Target, int HwMode) {
std::string IndexArray, StorageArray;
raw_string_ostream IS(IndexArray), SS(StorageArray);
const CodeGenHwModes &HWM = Target.getHwModes();
if (HwMode == -1) {
IS << " static const unsigned Index[][2] = {\n";
SS << " static const uint64_t InstBits[] = {\n";
} else {
StringRef Name = HWM.getMode(HwMode).Name;
IS << " static const unsigned Index_" << Name << "[][2] = {\n";
SS << " static const uint64_t InstBits_" << Name << "[] = {\n";
}
unsigned NumFixedValueWords = 0U;
for (const CodeGenInstruction *CGI : NumberedInstructions) {
Record *R = CGI->TheDef;
if (R->getValueAsString("Namespace") == "TargetOpcode" ||
R->getValueAsBit("isPseudo")) {
IS.indent(4) << "{/*NumBits*/0, /*Index*/0},\n";
continue;
}
Record *EncodingDef = R;
if (const RecordVal *RV = R->getValue("EncodingInfos")) {
if (auto *DI = dyn_cast_or_null<DefInit>(RV->getValue())) {
EncodingInfoByHwMode EBM(DI->getDef(), HWM);
if (EBM.hasMode(HwMode))
EncodingDef = EBM.get(HwMode);
}
}
auto It = VarLenInsts.find(EncodingDef);
if (It == VarLenInsts.end())
PrintFatalError(EncodingDef, "VarLenInst not found for this record");
const VarLenInst &VLI = It->second;
unsigned i = 0U, BitWidth = VLI.size();
// Start by filling in fixed values.
APInt Value(BitWidth, 0);
auto SI = VLI.begin(), SE = VLI.end();
// Scan through all the segments that have fixed-bits values.
while (i < BitWidth && SI != SE) {
unsigned SegmentNumBits = SI->BitWidth;
if (const auto *BI = dyn_cast<BitsInit>(SI->Value)) {
for (unsigned Idx = 0U; Idx != SegmentNumBits; ++Idx) {
auto *B = cast<BitInit>(BI->getBit(Idx));
Value.setBitVal(i + Idx, B->getValue());
}
}
if (const auto *BI = dyn_cast<BitInit>(SI->Value))
Value.setBitVal(i, BI->getValue());
i += SegmentNumBits;
++SI;
}
emitInstBits(IS, SS, Value, NumFixedValueWords);
IS << '\t' << "// " << R->getName() << "\n";
if (Value.getNumWords())
SS << '\t' << "// " << R->getName() << "\n";
}
IS.indent(4) << "{/*NumBits*/0, /*Index*/0}\n };\n";
SS.indent(4) << "UINT64_C(0)\n };\n";
OS << IS.str() << SS.str();
}
std::string VarLenCodeEmitterGen::getInstructionCase(Record *R,
CodeGenTarget &Target) {
std::string Case;
if (const RecordVal *RV = R->getValue("EncodingInfos")) {
if (auto *DI = dyn_cast_or_null<DefInit>(RV->getValue())) {
const CodeGenHwModes &HWM = Target.getHwModes();
EncodingInfoByHwMode EBM(DI->getDef(), HWM);
Case += " switch (HwMode) {\n";
Case += " default: llvm_unreachable(\"Unhandled HwMode\");\n";
for (auto &KV : EBM) {
Case += " case " + itostr(KV.first) + ": {\n";
Case += getInstructionCaseForEncoding(R, KV.second, Target);
Case += " break;\n";
Case += " }\n";
}
Case += " }\n";
return Case;
}
}
return getInstructionCaseForEncoding(R, R, Target);
}
std::string VarLenCodeEmitterGen::getInstructionCaseForEncoding(
Record *R, Record *EncodingDef, CodeGenTarget &Target) {
auto It = VarLenInsts.find(EncodingDef);
if (It == VarLenInsts.end())
PrintFatalError(EncodingDef, "Parsed encoding record not found");
const VarLenInst &VLI = It->second;
size_t BitWidth = VLI.size();
CodeGenInstruction &CGI = Target.getInstruction(R);
std::string Case;
raw_string_ostream SS(Case);
// Resize the scratch buffer.
if (BitWidth && !VLI.isFixedValueOnly())
SS.indent(6) << "Scratch = Scratch.zext(" << BitWidth << ");\n";
// Populate based value.
SS.indent(6) << "Inst = getInstBits(opcode);\n";
// Process each segment in VLI.
size_t Offset = 0U;
for (const auto &ES : VLI) {
unsigned NumBits = ES.BitWidth;
const Init *Val = ES.Value;
// If it's a StringInit or DagInit, it's a reference to an operand
// or part of an operand.
if (isa<StringInit>(Val) || isa<DagInit>(Val)) {
StringRef OperandName;
unsigned LoBit = 0U;
if (const auto *SV = dyn_cast<StringInit>(Val)) {
OperandName = SV->getValue();
} else {
// Normalized: (slice <operand name>, <high bit>, <low bit>)
const auto *DV = cast<DagInit>(Val);
OperandName = cast<StringInit>(DV->getArg(0))->getValue();
LoBit = static_cast<unsigned>(cast<IntInit>(DV->getArg(2))->getValue());
}
auto OpIdx = CGI.Operands.ParseOperandName(OperandName);
unsigned FlatOpIdx = CGI.Operands.getFlattenedOperandNumber(OpIdx);
StringRef CustomEncoder =
CGI.Operands[OpIdx.first].EncoderMethodNames[OpIdx.second];
if (ES.CustomEncoder.size())
CustomEncoder = ES.CustomEncoder;
SS.indent(6) << "Scratch.clearAllBits();\n";
SS.indent(6) << "// op: " << OperandName.drop_front(1) << "\n";
if (CustomEncoder.empty())
SS.indent(6) << "getMachineOpValue(MI, MI.getOperand("
<< utostr(FlatOpIdx) << ")";
else
SS.indent(6) << CustomEncoder << "(MI, /*OpIdx=*/" << utostr(FlatOpIdx);
SS << ", /*Pos=*/" << utostr(Offset) << ", Scratch, Fixups, STI);\n";
SS.indent(6) << "Inst.insertBits("
<< "Scratch.extractBits(" << utostr(NumBits) << ", "
<< utostr(LoBit) << ")"
<< ", " << Offset << ");\n";
}
Offset += NumBits;
}
StringRef PostEmitter = R->getValueAsString("PostEncoderMethod");
if (!PostEmitter.empty())
SS.indent(6) << "Inst = " << PostEmitter << "(MI, Inst, STI);\n";
return Case;
}
namespace llvm {
void emitVarLenCodeEmitter(RecordKeeper &R, raw_ostream &OS) {
VarLenCodeEmitterGen(R).run(OS);
}
} // end namespace llvm