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llvm/utils/TableGen/FastISelEmitter.cpp

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//===- FastISelEmitter.cpp - Generate an instruction selector -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This tablegen backend emits a "fast" instruction selector.
//
// This instruction selection method is designed to emit very poor code
// quickly. Also, it is not designed to do much lowering, so most illegal
// types (e.g. i64 on 32-bit targets) and operations (e.g. calls) are not
// supported and cannot easily be added. Blocks containing operations
// that are not supported need to be handled by a more capable selector,
// such as the SelectionDAG selector.
//
// The intended use for "fast" instruction selection is "-O0" mode
// compilation, where the quality of the generated code is irrelevant when
// weighed against the speed at which the code can be generated.
//
// If compile time is so important, you might wonder why we don't just
// skip codegen all-together, emit LLVM bytecode files, and execute them
// with an interpreter. The answer is that it would complicate linking and
// debugging, and also because that isn't how a compiler is expected to
// work in some circles.
//
// If you need better generated code or more lowering than what this
// instruction selector provides, use the SelectionDAG (DAGISel) instruction
// selector instead. If you're looking here because SelectionDAG isn't fast
// enough, consider looking into improving the SelectionDAG infastructure
// instead. At the time of this writing there remain several major
// opportunities for improvement.
//
//===----------------------------------------------------------------------===//
#include "FastISelEmitter.h"
#include "Record.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Streams.h"
#include "llvm/ADT/VectorExtras.h"
using namespace llvm;
namespace {
/// InstructionMemo - This class holds additional information about an
/// instruction needed to emit code for it.
///
struct InstructionMemo {
std::string Name;
const CodeGenRegisterClass *RC;
unsigned char SubRegNo;
std::vector<std::string>* PhysRegs;
};
/// OperandsSignature - This class holds a description of a list of operand
/// types. It has utility methods for emitting text based on the operands.
///
struct OperandsSignature {
std::vector<std::string> Operands;
bool operator<(const OperandsSignature &O) const {
return Operands < O.Operands;
}
bool empty() const { return Operands.empty(); }
/// initialize - Examine the given pattern and initialize the contents
/// of the Operands array accordingly. Return true if all the operands
/// are supported, false otherwise.
///
bool initialize(TreePatternNode *InstPatNode,
const CodeGenTarget &Target,
MVT::SimpleValueType VT) {
if (!InstPatNode->isLeaf() &&
InstPatNode->getOperator()->getName() == "imm") {
Operands.push_back("i");
return true;
}
if (!InstPatNode->isLeaf() &&
InstPatNode->getOperator()->getName() == "fpimm") {
Operands.push_back("f");
return true;
}
const CodeGenRegisterClass *DstRC = 0;
for (unsigned i = 0, e = InstPatNode->getNumChildren(); i != e; ++i) {
TreePatternNode *Op = InstPatNode->getChild(i);
// For now, filter out any operand with a predicate.
if (!Op->getPredicateFn().empty())
return false;
// For now, filter out any operand with multiple values.
if (Op->getExtTypes().size() != 1)
return false;
// For now, all the operands must have the same type.
if (Op->getTypeNum(0) != VT)
return false;
if (!Op->isLeaf()) {
if (Op->getOperator()->getName() == "imm") {
Operands.push_back("i");
return true;
}
if (Op->getOperator()->getName() == "fpimm") {
Operands.push_back("f");
return true;
}
// For now, ignore other non-leaf nodes.
return false;
}
DefInit *OpDI = dynamic_cast<DefInit*>(Op->getLeafValue());
if (!OpDI)
return false;
Record *OpLeafRec = OpDI->getDef();
// For now, the only other thing we accept is register operands.
const CodeGenRegisterClass *RC = 0;
if (OpLeafRec->isSubClassOf("RegisterClass"))
RC = &Target.getRegisterClass(OpLeafRec);
else if (OpLeafRec->isSubClassOf("Register"))
RC = Target.getRegisterClassForRegister(OpLeafRec);
else
return false;
// For now, require the register operands' register classes to all
// be the same.
if (!RC)
return false;
// For now, all the operands must have the same register class.
if (DstRC) {
if (DstRC != RC)
return false;
} else
DstRC = RC;
Operands.push_back("r");
}
return true;
}
void PrintParameters(std::ostream &OS) const {
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
if (Operands[i] == "r") {
OS << "unsigned Op" << i;
} else if (Operands[i] == "i") {
OS << "uint64_t imm" << i;
} else if (Operands[i] == "f") {
OS << "ConstantFP *f" << i;
} else {
assert("Unknown operand kind!");
abort();
}
if (i + 1 != e)
OS << ", ";
}
}
void PrintArguments(std::ostream &OS,
const std::vector<std::string>& PR) const {
assert(PR.size() == Operands.size());
bool PrintedArg = false;
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
if (PR[i] != "")
// Implicit physical register operand.
continue;
if (PrintedArg)
OS << ", ";
if (Operands[i] == "r") {
OS << "Op" << i;
PrintedArg = true;
} else if (Operands[i] == "i") {
OS << "imm" << i;
PrintedArg = true;
} else if (Operands[i] == "f") {
OS << "f" << i;
PrintedArg = true;
} else {
assert("Unknown operand kind!");
abort();
}
}
}
void PrintArguments(std::ostream &OS) const {
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
if (Operands[i] == "r") {
OS << "Op" << i;
} else if (Operands[i] == "i") {
OS << "imm" << i;
} else if (Operands[i] == "f") {
OS << "f" << i;
} else {
assert("Unknown operand kind!");
abort();
}
if (i + 1 != e)
OS << ", ";
}
}
void PrintManglingSuffix(std::ostream &OS,
const std::vector<std::string>& PR) const {
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
if (PR[i] != "")
// Implicit physical register operand. e.g. Instruction::Mul expect to
// select to a binary op. On x86, mul may take a single operand with
// the other operand being implicit. We must emit something that looks
// like a binary instruction except for the very inner FastEmitInst_*
// call.
continue;
OS << Operands[i];
}
}
void PrintManglingSuffix(std::ostream &OS) const {
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
OS << Operands[i];
}
}
};
class FastISelMap {
typedef std::map<std::string, InstructionMemo> PredMap;
typedef std::map<MVT::SimpleValueType, PredMap> RetPredMap;
typedef std::map<MVT::SimpleValueType, RetPredMap> TypeRetPredMap;
typedef std::map<std::string, TypeRetPredMap> OpcodeTypeRetPredMap;
typedef std::map<OperandsSignature, OpcodeTypeRetPredMap> OperandsOpcodeTypeRetPredMap;
OperandsOpcodeTypeRetPredMap SimplePatterns;
std::string InstNS;
public:
explicit FastISelMap(std::string InstNS);
void CollectPatterns(CodeGenDAGPatterns &CGP);
void PrintClass(std::ostream &OS);
void PrintFunctionDefinitions(std::ostream &OS);
};
}
static std::string getOpcodeName(Record *Op, CodeGenDAGPatterns &CGP) {
return CGP.getSDNodeInfo(Op).getEnumName();
}
static std::string getLegalCName(std::string OpName) {
std::string::size_type pos = OpName.find("::");
if (pos != std::string::npos)
OpName.replace(pos, 2, "_");
return OpName;
}
FastISelMap::FastISelMap(std::string instns)
: InstNS(instns) {
}
void FastISelMap::CollectPatterns(CodeGenDAGPatterns &CGP) {
const CodeGenTarget &Target = CGP.getTargetInfo();
// Determine the target's namespace name.
InstNS = Target.getInstNamespace() + "::";
assert(InstNS.size() > 2 && "Can't determine target-specific namespace!");
// Scan through all the patterns and record the simple ones.
for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
E = CGP.ptm_end(); I != E; ++I) {
const PatternToMatch &Pattern = *I;
// For now, just look at Instructions, so that we don't have to worry
// about emitting multiple instructions for a pattern.
TreePatternNode *Dst = Pattern.getDstPattern();
if (Dst->isLeaf()) continue;
Record *Op = Dst->getOperator();
if (!Op->isSubClassOf("Instruction"))
continue;
CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op->getName());
if (II.OperandList.empty())
continue;
// For now, ignore multi-instruction patterns.
bool MultiInsts = false;
for (unsigned i = 0, e = Dst->getNumChildren(); i != e; ++i) {
TreePatternNode *ChildOp = Dst->getChild(i);
if (ChildOp->isLeaf())
continue;
if (ChildOp->getOperator()->isSubClassOf("Instruction")) {
MultiInsts = true;
break;
}
}
if (MultiInsts)
continue;
// For now, ignore instructions where the first operand is not an
// output register.
const CodeGenRegisterClass *DstRC = 0;
unsigned SubRegNo = ~0;
if (Op->getName() != "EXTRACT_SUBREG") {
Record *Op0Rec = II.OperandList[0].Rec;
if (!Op0Rec->isSubClassOf("RegisterClass"))
continue;
DstRC = &Target.getRegisterClass(Op0Rec);
if (!DstRC)
continue;
} else {
SubRegNo = static_cast<IntInit*>(
Dst->getChild(1)->getLeafValue())->getValue();
}
// Inspect the pattern.
TreePatternNode *InstPatNode = Pattern.getSrcPattern();
if (!InstPatNode) continue;
if (InstPatNode->isLeaf()) continue;
Record *InstPatOp = InstPatNode->getOperator();
std::string OpcodeName = getOpcodeName(InstPatOp, CGP);
MVT::SimpleValueType RetVT = InstPatNode->getTypeNum(0);
MVT::SimpleValueType VT = RetVT;
if (InstPatNode->getNumChildren())
VT = InstPatNode->getChild(0)->getTypeNum(0);
// For now, filter out instructions which just set a register to
// an Operand or an immediate, like MOV32ri.
if (InstPatOp->isSubClassOf("Operand"))
continue;
// For now, filter out any instructions with predicates.
if (!InstPatNode->getPredicateFn().empty())
continue;
// Check all the operands.
OperandsSignature Operands;
if (!Operands.initialize(InstPatNode, Target, VT))
continue;
std::vector<std::string>* PhysRegInputs = new std::vector<std::string>();
if (!InstPatNode->isLeaf() &&
(InstPatNode->getOperator()->getName() == "imm" ||
InstPatNode->getOperator()->getName() == "fpimmm"))
PhysRegInputs->push_back("");
else if (!InstPatNode->isLeaf()) {
for (unsigned i = 0, e = InstPatNode->getNumChildren(); i != e; ++i) {
TreePatternNode *Op = InstPatNode->getChild(i);
if (!Op->isLeaf()) {
PhysRegInputs->push_back("");
continue;
}
DefInit *OpDI = dynamic_cast<DefInit*>(Op->getLeafValue());
Record *OpLeafRec = OpDI->getDef();
std::string PhysReg;
if (OpLeafRec->isSubClassOf("Register")) {
PhysReg += static_cast<StringInit*>(OpLeafRec->getValue( \
"Namespace")->getValue())->getValue();
PhysReg += "::";
std::vector<CodeGenRegister> Regs = Target.getRegisters();
for (unsigned i = 0; i < Regs.size(); ++i) {
if (Regs[i].TheDef == OpLeafRec) {
PhysReg += Regs[i].getName();
break;
}
}
}
PhysRegInputs->push_back(PhysReg);
}
} else
PhysRegInputs->push_back("");
// Get the predicate that guards this pattern.
std::string PredicateCheck = Pattern.getPredicateCheck();
// Ok, we found a pattern that we can handle. Remember it.
InstructionMemo Memo = {
Pattern.getDstPattern()->getOperator()->getName(),
DstRC,
SubRegNo,
PhysRegInputs
};
assert(!SimplePatterns[Operands][OpcodeName][VT][RetVT].count(PredicateCheck) &&
"Duplicate pattern!");
SimplePatterns[Operands][OpcodeName][VT][RetVT][PredicateCheck] = Memo;
}
}
void FastISelMap::PrintFunctionDefinitions(std::ostream &OS) {
// Now emit code for all the patterns that we collected.
for (OperandsOpcodeTypeRetPredMap::const_iterator OI = SimplePatterns.begin(),
OE = SimplePatterns.end(); OI != OE; ++OI) {
const OperandsSignature &Operands = OI->first;
const OpcodeTypeRetPredMap &OTM = OI->second;
for (OpcodeTypeRetPredMap::const_iterator I = OTM.begin(), E = OTM.end();
I != E; ++I) {
const std::string &Opcode = I->first;
const TypeRetPredMap &TM = I->second;
OS << "// FastEmit functions for " << Opcode << ".\n";
OS << "\n";
// Emit one function for each opcode,type pair.
for (TypeRetPredMap::const_iterator TI = TM.begin(), TE = TM.end();
TI != TE; ++TI) {
MVT::SimpleValueType VT = TI->first;
const RetPredMap &RM = TI->second;
if (RM.size() != 1) {
for (RetPredMap::const_iterator RI = RM.begin(), RE = RM.end();
RI != RE; ++RI) {
MVT::SimpleValueType RetVT = RI->first;
const PredMap &PM = RI->second;
bool HasPred = false;
OS << "unsigned FastEmit_"
<< getLegalCName(Opcode)
<< "_" << getLegalCName(getName(VT))
<< "_" << getLegalCName(getName(RetVT)) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(";
Operands.PrintParameters(OS);
OS << ") {\n";
// Emit code for each possible instruction. There may be
// multiple if there are subtarget concerns.
for (PredMap::const_iterator PI = PM.begin(), PE = PM.end();
PI != PE; ++PI) {
std::string PredicateCheck = PI->first;
const InstructionMemo &Memo = PI->second;
if (PredicateCheck.empty()) {
assert(!HasPred &&
"Multiple instructions match, at least one has "
"a predicate and at least one doesn't!");
} else {
OS << " if (" + PredicateCheck + ") {\n";
OS << " ";
HasPred = true;
}
for (unsigned i = 0; i < Memo.PhysRegs->size(); ++i) {
if ((*Memo.PhysRegs)[i] != "")
OS << " TII.copyRegToReg(*MBB, MBB->end(), "
<< (*Memo.PhysRegs)[i] << ", Op" << i << ", "
<< "TM.getRegisterInfo()->getPhysicalRegisterRegClass("
<< (*Memo.PhysRegs)[i] << "), "
<< "MRI.getRegClass(Op" << i << "));\n";
}
OS << " return FastEmitInst_";
if (Memo.SubRegNo == (unsigned char)~0) {
Operands.PrintManglingSuffix(OS, *Memo.PhysRegs);
OS << "(" << InstNS << Memo.Name << ", ";
OS << InstNS << Memo.RC->getName() << "RegisterClass";
if (!Operands.empty())
OS << ", ";
Operands.PrintArguments(OS, *Memo.PhysRegs);
OS << ");\n";
} else {
OS << "extractsubreg(Op0, ";
OS << (unsigned)Memo.SubRegNo;
OS << ");\n";
}
if (HasPred)
OS << " }\n";
}
// Return 0 if none of the predicates were satisfied.
if (HasPred)
OS << " return 0;\n";
OS << "}\n";
OS << "\n";
}
// Emit one function for the type that demultiplexes on return type.
OS << "unsigned FastEmit_"
<< getLegalCName(Opcode) << "_"
<< getLegalCName(getName(VT)) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(MVT::SimpleValueType RetVT";
if (!Operands.empty())
OS << ", ";
Operands.PrintParameters(OS);
OS << ") {\nswitch (RetVT) {\n";
for (RetPredMap::const_iterator RI = RM.begin(), RE = RM.end();
RI != RE; ++RI) {
MVT::SimpleValueType RetVT = RI->first;
OS << " case " << getName(RetVT) << ": return FastEmit_"
<< getLegalCName(Opcode) << "_" << getLegalCName(getName(VT))
<< "_" << getLegalCName(getName(RetVT)) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(";
Operands.PrintArguments(OS);
OS << ");\n";
}
OS << " default: return 0;\n}\n}\n\n";
} else {
// Non-variadic return type.
OS << "unsigned FastEmit_"
<< getLegalCName(Opcode) << "_"
<< getLegalCName(getName(VT)) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(MVT::SimpleValueType RetVT";
if (!Operands.empty())
OS << ", ";
Operands.PrintParameters(OS);
OS << ") {\n";
OS << " if (RetVT != " << getName(RM.begin()->first)
<< ")\n return 0;\n";
const PredMap &PM = RM.begin()->second;
bool HasPred = false;
// Emit code for each possible instruction. There may be
// multiple if there are subtarget concerns.
for (PredMap::const_iterator PI = PM.begin(), PE = PM.end(); PI != PE;
++PI) {
std::string PredicateCheck = PI->first;
const InstructionMemo &Memo = PI->second;
if (PredicateCheck.empty()) {
assert(!HasPred &&
"Multiple instructions match, at least one has "
"a predicate and at least one doesn't!");
} else {
OS << " if (" + PredicateCheck + ") {\n";
OS << " ";
HasPred = true;
}
for (unsigned i = 0; i < Memo.PhysRegs->size(); ++i) {
if ((*Memo.PhysRegs)[i] != "")
OS << " TII.copyRegToReg(*MBB, MBB->end(), "
<< (*Memo.PhysRegs)[i] << ", Op" << i << ", "
<< "TM.getRegisterInfo()->getPhysicalRegisterRegClass("
<< (*Memo.PhysRegs)[i] << "), "
<< "MRI.getRegClass(Op" << i << "));\n";
}
OS << " return FastEmitInst_";
if (Memo.SubRegNo == (unsigned char)~0) {
Operands.PrintManglingSuffix(OS, *Memo.PhysRegs);
OS << "(" << InstNS << Memo.Name << ", ";
OS << InstNS << Memo.RC->getName() << "RegisterClass";
if (!Operands.empty())
OS << ", ";
Operands.PrintArguments(OS, *Memo.PhysRegs);
OS << ");\n";
} else {
OS << "extractsubreg(Op0, ";
OS << (unsigned)Memo.SubRegNo;
OS << ");\n";
}
if (HasPred)
OS << " }\n";
}
// Return 0 if none of the predicates were satisfied.
if (HasPred)
OS << " return 0;\n";
OS << "}\n";
OS << "\n";
}
}
// Emit one function for the opcode that demultiplexes based on the type.
OS << "unsigned FastEmit_"
<< getLegalCName(Opcode) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(MVT::SimpleValueType VT, MVT::SimpleValueType RetVT";
if (!Operands.empty())
OS << ", ";
Operands.PrintParameters(OS);
OS << ") {\n";
OS << " switch (VT) {\n";
for (TypeRetPredMap::const_iterator TI = TM.begin(), TE = TM.end();
TI != TE; ++TI) {
MVT::SimpleValueType VT = TI->first;
std::string TypeName = getName(VT);
OS << " case " << TypeName << ": return FastEmit_"
<< getLegalCName(Opcode) << "_" << getLegalCName(TypeName) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(RetVT";
if (!Operands.empty())
OS << ", ";
Operands.PrintArguments(OS);
OS << ");\n";
}
OS << " default: return 0;\n";
OS << " }\n";
OS << "}\n";
OS << "\n";
}
OS << "// Top-level FastEmit function.\n";
OS << "\n";
// Emit one function for the operand signature that demultiplexes based
// on opcode and type.
OS << "unsigned FastEmit_";
Operands.PrintManglingSuffix(OS);
OS << "(MVT::SimpleValueType VT, MVT::SimpleValueType RetVT, ISD::NodeType Opcode";
if (!Operands.empty())
OS << ", ";
Operands.PrintParameters(OS);
OS << ") {\n";
OS << " switch (Opcode) {\n";
for (OpcodeTypeRetPredMap::const_iterator I = OTM.begin(), E = OTM.end();
I != E; ++I) {
const std::string &Opcode = I->first;
OS << " case " << Opcode << ": return FastEmit_"
<< getLegalCName(Opcode) << "_";
Operands.PrintManglingSuffix(OS);
OS << "(VT, RetVT";
if (!Operands.empty())
OS << ", ";
Operands.PrintArguments(OS);
OS << ");\n";
}
OS << " default: return 0;\n";
OS << " }\n";
OS << "}\n";
OS << "\n";
}
}
void FastISelEmitter::run(std::ostream &OS) {
const CodeGenTarget &Target = CGP.getTargetInfo();
// Determine the target's namespace name.
std::string InstNS = Target.getInstNamespace() + "::";
assert(InstNS.size() > 2 && "Can't determine target-specific namespace!");
EmitSourceFileHeader("\"Fast\" Instruction Selector for the " +
Target.getName() + " target", OS);
FastISelMap F(InstNS);
F.CollectPatterns(CGP);
F.PrintFunctionDefinitions(OS);
}
FastISelEmitter::FastISelEmitter(RecordKeeper &R)
: Records(R),
CGP(R) {
}
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