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

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//===- CodeEmitterGen.cpp - Code Emitter Generator ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 "CodeEmitterGen.h"
#include "CodeGenTarget.h"
#include "Record.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <map>
using namespace llvm;
// FIXME: Somewhat hackish to use a command line option for this. There should
// be a CodeEmitter class in the Target.td that controls this sort of thing
// instead.
static cl::opt<bool>
MCEmitter("mc-emitter",
cl::desc("Generate CodeEmitter for use with the MC library."),
cl::init(false));
void CodeEmitterGen::reverseBits(std::vector<Record*> &Insts) {
for (std::vector<Record*>::iterator I = Insts.begin(), E = Insts.end();
I != E; ++I) {
Record *R = *I;
if (R->getValueAsString("Namespace") == "TargetOpcode")
continue;
BitsInit *BI = R->getValueAsBitsInit("Inst");
unsigned numBits = BI->getNumBits();
BitsInit *NewBI = new BitsInit(numBits);
for (unsigned bit = 0, end = numBits / 2; bit != end; ++bit) {
unsigned bitSwapIdx = numBits - bit - 1;
Init *OrigBit = BI->getBit(bit);
Init *BitSwap = BI->getBit(bitSwapIdx);
NewBI->setBit(bit, BitSwap);
NewBI->setBit(bitSwapIdx, OrigBit);
}
if (numBits % 2) {
unsigned middle = (numBits + 1) / 2;
NewBI->setBit(middle, BI->getBit(middle));
}
// Update the bits in reversed order so that emitInstrOpBits will get the
// correct endianness.
R->getValue("Inst")->setValue(NewBI);
}
}
// 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 = dynamic_cast<VarBitInit*>(BI->getBit(bit)))
if (VarInit *VI = dynamic_cast<VarInit*>(VBI->getVariable()))
if (VI->getName() == VarName)
return VBI->getBitNum();
return -1;
}
void CodeEmitterGen::
AddCodeToMergeInOperand(Record *R, BitsInit *BI, const std::string &VarName,
unsigned &NumberedOp,
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 {
/// If this operand is not supposed to be emitted by the
/// generated emitter, skip it.
while (CGI.Operands.isFlatOperandNotEmitted(NumberedOp))
++NumberedOp;
OpIdx = NumberedOp++;
}
std::pair<unsigned, unsigned> SO = CGI.Operands.getSubOperandNumber(OpIdx);
std::string &EncoderMethodName = CGI.Operands[SO.first].EncoderMethodName;
// 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" +
" op = " + EncoderMethodName + "(MI, " + utostr(OpIdx);
if (MCEmitter)
Case += ", Fixups";
Case += ");\n";
}
} else {
Case += " // op: " + VarName + "\n" +
" op = getMachineOpValue(MI, MI.getOperand(" + utostr(OpIdx) + ")";
if (MCEmitter)
Case += ", Fixups";
Case += ");\n";
}
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;
}
unsigned opMask = ~0U >> (32-N);
int opShift = beginVarBit - N + 1;
opMask <<= opShift;
opShift = beginInstBit - beginVarBit;
if (opShift > 0) {
Case += " Value |= (op & " + utostr(opMask) + "U) << " +
itostr(opShift) + ";\n";
} else if (opShift < 0) {
Case += " Value |= (op & " + utostr(opMask) + "U) >> " +
itostr(-opShift) + ";\n";
} else {
Case += " Value |= op & " + utostr(opMask) + "U;\n";
}
}
}
std::string CodeEmitterGen::getInstructionCase(Record *R,
CodeGenTarget &Target) {
std::string Case;
BitsInit *BI = R->getValueAsBitsInit("Inst");
const std::vector<RecordVal> &Vals = R->getValues();
unsigned NumberedOp = 0;
// Loop over all of the fields in the instruction, determining which are the
// operands to the instruction.
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;
AddCodeToMergeInOperand(R, BI, Vals[i].getName(), NumberedOp, Case, Target);
}
std::string PostEmitter = R->getValueAsString("PostEncoderMethod");
if (!PostEmitter.empty())
Case += " Value = " + PostEmitter + "(MI, Value);\n";
return Case;
}
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
if (Target.isLittleEndianEncoding()) reverseBits(Insts);
EmitSourceFileHeader("Machine Code Emitter", o);
const std::vector<const CodeGenInstruction*> &NumberedInstructions =
Target.getInstructionsByEnumValue();
// Emit function declaration
o << "unsigned " << Target.getName();
if (MCEmitter)
o << "MCCodeEmitter::getBinaryCodeForInstr(const MCInst &MI,\n"
<< " SmallVectorImpl<MCFixup> &Fixups) const {\n";
else
o << "CodeEmitter::getBinaryCodeForInstr(const MachineInstr &MI) const {\n";
// Emit instruction base values
o << " static const unsigned InstBits[] = {\n";
for (std::vector<const CodeGenInstruction*>::const_iterator
IN = NumberedInstructions.begin(),
EN = NumberedInstructions.end();
IN != EN; ++IN) {
const CodeGenInstruction *CGI = *IN;
Record *R = CGI->TheDef;
if (R->getValueAsString("Namespace") == "TargetOpcode") {
o << " 0U,\n";
continue;
}
BitsInit *BI = R->getValueAsBitsInit("Inst");
// Start by filling in fixed values.
unsigned Value = 0;
for (unsigned i = 0, e = BI->getNumBits(); i != e; ++i) {
if (BitInit *B = dynamic_cast<BitInit*>(BI->getBit(e-i-1)))
Value |= B->getValue() << (e-i-1);
}
o << " " << Value << "U," << '\t' << "// " << R->getName() << "\n";
}
o << " 0U\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 (std::vector<Record*>::iterator IC = Insts.begin(), EC = Insts.end();
IC != EC; ++IC) {
Record *R = *IC;
if (R->getValueAsString("Namespace") == "TargetOpcode")
continue;
const std::string &InstName = R->getValueAsString("Namespace") + "::"
+ R->getName();
std::string Case = getInstructionCase(R, Target);
CaseMap[Case].push_back(InstName);
}
// Emit initial function code
o << " const unsigned opcode = MI.getOpcode();\n"
<< " unsigned Value = InstBits[opcode];\n"
<< " unsigned 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"
<< " return Value;\n"
<< "}\n\n";
}
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