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llvm-for-llvmta/utils/TableGen/CodeEmitterGen.cpp

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2022-04-25 10:02:23 +02:00
//===- CodeEmitterGen.cpp - Code Emitter 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
//
//===----------------------------------------------------------------------===//
//
// CodeEmitterGen uses the descriptions of instructions and their fields to
// construct an automated code emitter: a function that, given a MachineInstr,
// returns the (currently, 32-bit unsigned) value of the instruction.
//
//===----------------------------------------------------------------------===//
#include "CodeGenInstruction.h"
#include "CodeGenTarget.h"
#include "SubtargetFeatureInfo.h"
#include "Types.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TableGen/Record.h"
#include "llvm/TableGen/TableGenBackend.h"
#include <cassert>
#include <cstdint>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>
using namespace llvm;
namespace {
class CodeEmitterGen {
RecordKeeper &Records;
public:
CodeEmitterGen(RecordKeeper &R) : Records(R) {}
void run(raw_ostream &o);
private:
int getVariableBit(const std::string &VarName, BitsInit *BI, int bit);
std::string getInstructionCase(Record *R, CodeGenTarget &Target);
std::string getInstructionCaseForEncoding(Record *R, Record *EncodingDef,
CodeGenTarget &Target);
void AddCodeToMergeInOperand(Record *R, BitsInit *BI,
const std::string &VarName,
unsigned &NumberedOp,
std::set<unsigned> &NamedOpIndices,
std::string &Case, CodeGenTarget &Target);
void emitInstructionBaseValues(
raw_ostream &o, ArrayRef<const CodeGenInstruction *> NumberedInstructions,
CodeGenTarget &Target, int HwMode = -1);
unsigned BitWidth;
bool UseAPInt;
};
// If the VarBitInit at position 'bit' matches the specified variable then
// return the variable bit position. Otherwise return -1.
int CodeEmitterGen::getVariableBit(const std::string &VarName,
BitsInit *BI, int bit) {
if (VarBitInit *VBI = dyn_cast<VarBitInit>(BI->getBit(bit))) {
if (VarInit *VI = dyn_cast<VarInit>(VBI->getBitVar()))
if (VI->getName() == VarName)
return VBI->getBitNum();
} else if (VarInit *VI = dyn_cast<VarInit>(BI->getBit(bit))) {
if (VI->getName() == VarName)
return 0;
}
return -1;
}
void CodeEmitterGen::
AddCodeToMergeInOperand(Record *R, BitsInit *BI, const std::string &VarName,
unsigned &NumberedOp,
std::set<unsigned> &NamedOpIndices,
std::string &Case, CodeGenTarget &Target) {
CodeGenInstruction &CGI = Target.getInstruction(R);
// Determine if VarName actually contributes to the Inst encoding.
int bit = BI->getNumBits()-1;
// Scan for a bit that this contributed to.
for (; bit >= 0; ) {
if (getVariableBit(VarName, BI, bit) != -1)
break;
--bit;
}
// If we found no bits, ignore this value, otherwise emit the call to get the
// operand encoding.
if (bit < 0) return;
// If the operand matches by name, reference according to that
// operand number. Non-matching operands are assumed to be in
// order.
unsigned OpIdx;
if (CGI.Operands.hasOperandNamed(VarName, OpIdx)) {
// Get the machine operand number for the indicated operand.
OpIdx = CGI.Operands[OpIdx].MIOperandNo;
assert(!CGI.Operands.isFlatOperandNotEmitted(OpIdx) &&
"Explicitly used operand also marked as not emitted!");
} else {
unsigned NumberOps = CGI.Operands.size();
/// If this operand is not supposed to be emitted by the
/// generated emitter, skip it.
while (NumberedOp < NumberOps &&
(CGI.Operands.isFlatOperandNotEmitted(NumberedOp) ||
(!NamedOpIndices.empty() && NamedOpIndices.count(
CGI.Operands.getSubOperandNumber(NumberedOp).first)))) {
++NumberedOp;
if (NumberedOp >= CGI.Operands.back().MIOperandNo +
CGI.Operands.back().MINumOperands) {
errs() << "Too few operands in record " << R->getName() <<
" (no match for variable " << VarName << "):\n";
errs() << *R;
errs() << '\n';
return;
}
}
OpIdx = NumberedOp++;
}
std::pair<unsigned, unsigned> SO = CGI.Operands.getSubOperandNumber(OpIdx);
std::string &EncoderMethodName = CGI.Operands[SO.first].EncoderMethodName;
if (UseAPInt)
Case += " op.clearAllBits();\n";
// If the source operand has a custom encoder, use it. This will
// get the encoding for all of the suboperands.
if (!EncoderMethodName.empty()) {
// A custom encoder has all of the information for the
// sub-operands, if there are more than one, so only
// query the encoder once per source operand.
if (SO.second == 0) {
Case += " // op: " + VarName + "\n";
if (UseAPInt) {
Case += " " + EncoderMethodName + "(MI, " + utostr(OpIdx);
Case += ", op";
} else {
Case += " op = " + EncoderMethodName + "(MI, " + utostr(OpIdx);
}
Case += ", Fixups, STI);\n";
}
} else {
Case += " // op: " + VarName + "\n";
if (UseAPInt) {
Case += " getMachineOpValue(MI, MI.getOperand(" + utostr(OpIdx) + ")";
Case += ", op, Fixups, STI";
} else {
Case += " op = getMachineOpValue(MI, MI.getOperand(" + utostr(OpIdx) + ")";
Case += ", Fixups, STI";
}
Case += ");\n";
}
// Precalculate the number of lits this variable contributes to in the
// operand. If there is a single lit (consecutive range of bits) we can use a
// destructive sequence on APInt that reduces memory allocations.
int numOperandLits = 0;
for (int tmpBit = bit; tmpBit >= 0;) {
int varBit = getVariableBit(VarName, BI, tmpBit);
// If this bit isn't from a variable, skip it.
if (varBit == -1) {
--tmpBit;
continue;
}
// Figure out the consecutive range of bits covered by this operand, in
// order to generate better encoding code.
int beginVarBit = varBit;
int N = 1;
for (--tmpBit; tmpBit >= 0;) {
varBit = getVariableBit(VarName, BI, tmpBit);
if (varBit == -1 || varBit != (beginVarBit - N))
break;
++N;
--tmpBit;
}
++numOperandLits;
}
for (; bit >= 0; ) {
int varBit = getVariableBit(VarName, BI, bit);
// If this bit isn't from a variable, skip it.
if (varBit == -1) {
--bit;
continue;
}
// Figure out the consecutive range of bits covered by this operand, in
// order to generate better encoding code.
int beginInstBit = bit;
int beginVarBit = varBit;
int N = 1;
for (--bit; bit >= 0;) {
varBit = getVariableBit(VarName, BI, bit);
if (varBit == -1 || varBit != (beginVarBit - N)) break;
++N;
--bit;
}
std::string maskStr;
int opShift;
unsigned loBit = beginVarBit - N + 1;
unsigned hiBit = loBit + N;
unsigned loInstBit = beginInstBit - N + 1;
if (UseAPInt) {
std::string extractStr;
if (N >= 64) {
extractStr = "op.extractBits(" + itostr(hiBit - loBit) + ", " +
itostr(loBit) + ")";
Case += " Value.insertBits(" + extractStr + ", " +
itostr(loInstBit) + ");\n";
} else {
extractStr = "op.extractBitsAsZExtValue(" + itostr(hiBit - loBit) +
", " + itostr(loBit) + ")";
Case += " Value.insertBits(" + extractStr + ", " +
itostr(loInstBit) + ", " + itostr(hiBit - loBit) + ");\n";
}
} else {
uint64_t opMask = ~(uint64_t)0 >> (64 - N);
opShift = beginVarBit - N + 1;
opMask <<= opShift;
maskStr = "UINT64_C(" + utostr(opMask) + ")";
opShift = beginInstBit - beginVarBit;
if (numOperandLits == 1) {
Case += " op &= " + maskStr + ";\n";
if (opShift > 0) {
Case += " op <<= " + itostr(opShift) + ";\n";
} else if (opShift < 0) {
Case += " op >>= " + itostr(-opShift) + ";\n";
}
Case += " Value |= op;\n";
} else {
if (opShift > 0) {
Case += " Value |= (op & " + maskStr + ") << " +
itostr(opShift) + ";\n";
} else if (opShift < 0) {
Case += " Value |= (op & " + maskStr + ") >> " +
itostr(-opShift) + ";\n";
} else {
Case += " Value |= (op & " + maskStr + ");\n";
}
}
}
}
}
std::string CodeEmitterGen::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.Map) {
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 CodeEmitterGen::getInstructionCaseForEncoding(Record *R, Record *EncodingDef,
CodeGenTarget &Target) {
std::string Case;
BitsInit *BI = EncodingDef->getValueAsBitsInit("Inst");
unsigned NumberedOp = 0;
std::set<unsigned> NamedOpIndices;
// Collect the set of operand indices that might correspond to named
// operand, and skip these when assigning operands based on position.
if (Target.getInstructionSet()->
getValueAsBit("noNamedPositionallyEncodedOperands")) {
CodeGenInstruction &CGI = Target.getInstruction(R);
for (const RecordVal &RV : R->getValues()) {
unsigned OpIdx;
if (!CGI.Operands.hasOperandNamed(RV.getName(), OpIdx))
continue;
NamedOpIndices.insert(OpIdx);
}
}
// Loop over all of the fields in the instruction, determining which are the
// operands to the instruction.
for (const RecordVal &RV : EncodingDef->getValues()) {
// Ignore fixed fields in the record, we're looking for values like:
// bits<5> RST = { ?, ?, ?, ?, ? };
if (RV.isNonconcreteOK() || RV.getValue()->isComplete())
continue;
AddCodeToMergeInOperand(R, BI, std::string(RV.getName()), NumberedOp,
NamedOpIndices, Case, Target);
}
StringRef PostEmitter = R->getValueAsString("PostEncoderMethod");
if (!PostEmitter.empty()) {
Case += " Value = ";
Case += PostEmitter;
Case += "(MI, Value";
Case += ", STI";
Case += ");\n";
}
return Case;
}
static std::string
getNameForFeatureBitset(const std::vector<Record *> &FeatureBitset) {
std::string Name = "CEFBS";
for (const auto &Feature : FeatureBitset)
Name += ("_" + Feature->getName()).str();
return Name;
}
static void emitInstBits(raw_ostream &OS, const APInt &Bits) {
for (unsigned I = 0; I < Bits.getNumWords(); ++I)
OS << ((I > 0) ? ", " : "") << "UINT64_C(" << utostr(Bits.getRawData()[I])
<< ")";
}
void CodeEmitterGen::emitInstructionBaseValues(
raw_ostream &o, ArrayRef<const CodeGenInstruction *> NumberedInstructions,
CodeGenTarget &Target, int HwMode) {
const CodeGenHwModes &HWM = Target.getHwModes();
if (HwMode == -1)
o << " static const uint64_t InstBits[] = {\n";
else
o << " static const uint64_t InstBits_" << HWM.getMode(HwMode).Name
<< "[] = {\n";
for (const CodeGenInstruction *CGI : NumberedInstructions) {
Record *R = CGI->TheDef;
if (R->getValueAsString("Namespace") == "TargetOpcode" ||
R->getValueAsBit("isPseudo")) {
o << " "; emitInstBits(o, APInt(BitWidth, 0)); o << ",\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);
}
}
BitsInit *BI = EncodingDef->getValueAsBitsInit("Inst");
// Start by filling in fixed values.
APInt Value(BitWidth, 0);
for (unsigned i = 0, e = BI->getNumBits(); i != e; ++i) {
if (BitInit *B = dyn_cast<BitInit>(BI->getBit(e - i - 1)))
Value |= APInt(BitWidth, (uint64_t)B->getValue()) << (e - i - 1);
}
o << " ";
emitInstBits(o, Value);
o << "," << '\t' << "// " << R->getName() << "\n";
}
o << " UINT64_C(0)\n };\n";
}
void CodeEmitterGen::run(raw_ostream &o) {
CodeGenTarget Target(Records);
std::vector<Record*> Insts = Records.getAllDerivedDefinitions("Instruction");
// For little-endian instruction bit encodings, reverse the bit order
Target.reverseBitsForLittleEndianEncoding();
ArrayRef<const CodeGenInstruction*> NumberedInstructions =
Target.getInstructionsByEnumValue();
const CodeGenHwModes &HWM = Target.getHwModes();
// The set of HwModes used by instruction encodings.
std::set<unsigned> HwModes;
BitWidth = 0;
for (const CodeGenInstruction *CGI : NumberedInstructions) {
Record *R = CGI->TheDef;
if (R->getValueAsString("Namespace") == "TargetOpcode" ||
R->getValueAsBit("isPseudo"))
continue;
if (const RecordVal *RV = R->getValue("EncodingInfos")) {
if (DefInit *DI = dyn_cast_or_null<DefInit>(RV->getValue())) {
EncodingInfoByHwMode EBM(DI->getDef(), HWM);
for (auto &KV : EBM.Map) {
BitsInit *BI = KV.second->getValueAsBitsInit("Inst");
BitWidth = std::max(BitWidth, BI->getNumBits());
HwModes.insert(KV.first);
}
continue;
}
}
BitsInit *BI = R->getValueAsBitsInit("Inst");
BitWidth = std::max(BitWidth, BI->getNumBits());
}
UseAPInt = BitWidth > 64;
// Emit function declaration
if (UseAPInt) {
o << "void " << Target.getName()
<< "MCCodeEmitter::getBinaryCodeForInstr(const MCInst &MI,\n"
<< " SmallVectorImpl<MCFixup> &Fixups,\n"
<< " APInt &Inst,\n"
<< " APInt &Scratch,\n"
<< " const MCSubtargetInfo &STI) const {\n";
} else {
o << "uint64_t " << Target.getName();
o << "MCCodeEmitter::getBinaryCodeForInstr(const MCInst &MI,\n"
<< " SmallVectorImpl<MCFixup> &Fixups,\n"
<< " const MCSubtargetInfo &STI) const {\n";
}
// Emit instruction base values
if (HwModes.empty()) {
emitInstructionBaseValues(o, NumberedInstructions, Target, -1);
} else {
for (unsigned HwMode : HwModes)
emitInstructionBaseValues(o, NumberedInstructions, Target, (int)HwMode);
}
if (!HwModes.empty()) {
o << " const uint64_t *InstBits;\n";
o << " unsigned HwMode = STI.getHwMode();\n";
o << " switch (HwMode) {\n";
o << " default: llvm_unreachable(\"Unknown hardware mode!\"); break;\n";
for (unsigned I : HwModes) {
o << " case " << I << ": InstBits = InstBits_" << HWM.getMode(I).Name
<< "; break;\n";
}
o << " };\n";
}
// Map to accumulate all the cases.
std::map<std::string, std::vector<std::string>> CaseMap;
// Construct all cases statement for each opcode
for (std::vector<Record*>::iterator IC = Insts.begin(), EC = Insts.end();
IC != EC; ++IC) {
Record *R = *IC;
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
if (UseAPInt) {
int NumWords = APInt::getNumWords(BitWidth);
int NumBytes = (BitWidth + 7) / 8;
o << " const unsigned opcode = MI.getOpcode();\n"
<< " if (Inst.getBitWidth() != " << BitWidth << ")\n"
<< " Inst = Inst.zext(" << BitWidth << ");\n"
<< " if (Scratch.getBitWidth() != " << BitWidth << ")\n"
<< " Scratch = Scratch.zext(" << BitWidth << ");\n"
<< " LoadIntFromMemory(Inst, (uint8_t *)&InstBits[opcode * " << NumWords
<< "], " << NumBytes << ");\n"
<< " APInt &Value = Inst;\n"
<< " APInt &op = Scratch;\n"
<< " switch (opcode) {\n";
} else {
o << " const unsigned opcode = MI.getOpcode();\n"
<< " uint64_t Value = InstBits[opcode];\n"
<< " uint64_t op = 0;\n"
<< " (void)op; // suppress warning\n"
<< " switch (opcode) {\n";
}
// Emit each case statement
std::map<std::string, std::vector<std::string>>::iterator IE, EE;
for (IE = CaseMap.begin(), EE = CaseMap.end(); IE != EE; ++IE) {
const std::string &Case = IE->first;
std::vector<std::string> &InstList = IE->second;
for (int i = 0, N = InstList.size(); i < N; i++) {
if (i) o << "\n";
o << " case " << InstList[i] << ":";
}
o << " {\n";
o << Case;
o << " break;\n"
<< " }\n";
}
// Default case: unhandled opcode
o << " default:\n"
<< " std::string msg;\n"
<< " raw_string_ostream Msg(msg);\n"
<< " Msg << \"Not supported instr: \" << MI;\n"
<< " report_fatal_error(Msg.str());\n"
<< " }\n";
if (UseAPInt)
o << " Inst = Value;\n";
else
o << " return Value;\n";
o << "}\n\n";
const auto &All = SubtargetFeatureInfo::getAll(Records);
std::map<Record *, SubtargetFeatureInfo, LessRecordByID> SubtargetFeatures;
SubtargetFeatures.insert(All.begin(), All.end());
o << "#ifdef ENABLE_INSTR_PREDICATE_VERIFIER\n"
<< "#undef ENABLE_INSTR_PREDICATE_VERIFIER\n"
<< "#include <sstream>\n\n";
// Emit the subtarget feature enumeration.
SubtargetFeatureInfo::emitSubtargetFeatureBitEnumeration(SubtargetFeatures,
o);
// Emit the name table for error messages.
o << "#ifndef NDEBUG\n";
SubtargetFeatureInfo::emitNameTable(SubtargetFeatures, o);
o << "#endif // NDEBUG\n";
// Emit the available features compute function.
SubtargetFeatureInfo::emitComputeAssemblerAvailableFeatures(
Target.getName(), "MCCodeEmitter", "computeAvailableFeatures",
SubtargetFeatures, o);
std::vector<std::vector<Record *>> FeatureBitsets;
for (const CodeGenInstruction *Inst : Target.getInstructionsByEnumValue()) {
FeatureBitsets.emplace_back();
for (Record *Predicate : Inst->TheDef->getValueAsListOfDefs("Predicates")) {
const auto &I = SubtargetFeatures.find(Predicate);
if (I != SubtargetFeatures.end())
FeatureBitsets.back().push_back(I->second.TheDef);
}
}
llvm::sort(FeatureBitsets, [&](const std::vector<Record *> &A,
const std::vector<Record *> &B) {
if (A.size() < B.size())
return true;
if (A.size() > B.size())
return false;
for (auto Pair : zip(A, B)) {
if (std::get<0>(Pair)->getName() < std::get<1>(Pair)->getName())
return true;
if (std::get<0>(Pair)->getName() > std::get<1>(Pair)->getName())
return false;
}
return false;
});
FeatureBitsets.erase(
std::unique(FeatureBitsets.begin(), FeatureBitsets.end()),
FeatureBitsets.end());
o << "#ifndef NDEBUG\n"
<< "// Feature bitsets.\n"
<< "enum : " << getMinimalTypeForRange(FeatureBitsets.size()) << " {\n"
<< " CEFBS_None,\n";
for (const auto &FeatureBitset : FeatureBitsets) {
if (FeatureBitset.empty())
continue;
o << " " << getNameForFeatureBitset(FeatureBitset) << ",\n";
}
o << "};\n\n"
<< "static constexpr FeatureBitset FeatureBitsets[] = {\n"
<< " {}, // CEFBS_None\n";
for (const auto &FeatureBitset : FeatureBitsets) {
if (FeatureBitset.empty())
continue;
o << " {";
for (const auto &Feature : FeatureBitset) {
const auto &I = SubtargetFeatures.find(Feature);
assert(I != SubtargetFeatures.end() && "Didn't import predicate?");
o << I->second.getEnumBitName() << ", ";
}
o << "},\n";
}
o << "};\n"
<< "#endif // NDEBUG\n\n";
// Emit the predicate verifier.
o << "void " << Target.getName()
<< "MCCodeEmitter::verifyInstructionPredicates(\n"
<< " const MCInst &Inst, const FeatureBitset &AvailableFeatures) const {\n"
<< "#ifndef NDEBUG\n"
<< " static " << getMinimalTypeForRange(FeatureBitsets.size())
<< " RequiredFeaturesRefs[] = {\n";
unsigned InstIdx = 0;
for (const CodeGenInstruction *Inst : Target.getInstructionsByEnumValue()) {
o << " CEFBS";
unsigned NumPredicates = 0;
for (Record *Predicate : Inst->TheDef->getValueAsListOfDefs("Predicates")) {
const auto &I = SubtargetFeatures.find(Predicate);
if (I != SubtargetFeatures.end()) {
o << '_' << I->second.TheDef->getName();
NumPredicates++;
}
}
if (!NumPredicates)
o << "_None";
o << ", // " << Inst->TheDef->getName() << " = " << InstIdx << "\n";
InstIdx++;
}
o << " };\n\n";
o << " assert(Inst.getOpcode() < " << InstIdx << ");\n";
o << " const FeatureBitset &RequiredFeatures = "
"FeatureBitsets[RequiredFeaturesRefs[Inst.getOpcode()]];\n";
o << " FeatureBitset MissingFeatures =\n"
<< " (AvailableFeatures & RequiredFeatures) ^\n"
<< " RequiredFeatures;\n"
<< " if (MissingFeatures.any()) {\n"
<< " std::ostringstream Msg;\n"
<< " Msg << \"Attempting to emit \" << "
"MCII.getName(Inst.getOpcode()).str()\n"
<< " << \" instruction but the \";\n"
<< " for (unsigned i = 0, e = MissingFeatures.size(); i != e; ++i)\n"
<< " if (MissingFeatures.test(i))\n"
<< " Msg << SubtargetFeatureNames[i] << \" \";\n"
<< " Msg << \"predicate(s) are not met\";\n"
<< " report_fatal_error(Msg.str());\n"
<< " }\n"
<< "#else\n"
<< " // Silence unused variable warning on targets that don't use MCII for "
"other purposes (e.g. BPF).\n"
<< " (void)MCII;\n"
<< "#endif // NDEBUG\n";
o << "}\n";
o << "#endif\n";
}
} // end anonymous namespace
namespace llvm {
void EmitCodeEmitter(RecordKeeper &RK, raw_ostream &OS) {
emitSourceFileHeader("Machine Code Emitter", OS);
CodeEmitterGen(RK).run(OS);
}
} // end namespace llvm