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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/Debug.h"
using namespace llvm;
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->getName() == "PHI" ||
R->getName() == "INLINEASM" ||
R->getName() == "DBG_LABEL" ||
R->getName() == "EH_LABEL" ||
R->getName() == "GC_LABEL" ||
R->getName() == "DECLARE" ||
R->getName() == "EXTRACT_SUBREG" ||
R->getName() == "INSERT_SUBREG" ||
R->getName() == "IMPLICIT_DEF" ||
R->getName() == "SUBREG_TO_REG") 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))) {
TypedInit *TI = VBI->getVariable();
if (VarInit *VI = dynamic_cast<VarInit*>(TI)) {
if (VI->getName() == VarName) return VBI->getBitNum();
}
}
return -1;
}
void CodeEmitterGen::run(std::ostream &o) {
CodeGenTarget Target;
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);
std::string Namespace = Insts[0]->getValueAsString("Namespace") + "::";
std::vector<const CodeGenInstruction*> NumberedInstructions;
Target.getInstructionsByEnumValue(NumberedInstructions);
// Emit function declaration
o << "unsigned " << Target.getName() << "CodeEmitter::"
<< "getBinaryCodeForInstr(const MachineInstr &MI) {\n";
// Emit instruction base values
o << " static const unsigned InstBits[] = {\n";
for (std::vector<const CodeGenInstruction*>::iterator
IN = NumberedInstructions.begin(),
EN = NumberedInstructions.end();
IN != EN; ++IN) {
const CodeGenInstruction *CGI = *IN;
Record *R = CGI->TheDef;
if (R->getName() == "PHI" ||
R->getName() == "INLINEASM" ||
R->getName() == "DBG_LABEL" ||
R->getName() == "EH_LABEL" ||
R->getName() == "GC_LABEL" ||
R->getName() == "DECLARE" ||
R->getName() == "EXTRACT_SUBREG" ||
R->getName() == "INSERT_SUBREG" ||
R->getName() == "IMPLICIT_DEF" ||
R->getName() == "SUBREG_TO_REG") {
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;
const std::string &InstName = R->getName();
std::string Case("");
if (InstName == "PHI" ||
InstName == "INLINEASM" ||
InstName == "DBG_LABEL"||
InstName == "EH_LABEL"||
InstName == "GC_LABEL"||
InstName == "DECLARE"||
InstName == "EXTRACT_SUBREG" ||
InstName == "INSERT_SUBREG" ||
InstName == "IMPLICIT_DEF" ||
InstName == "SUBREG_TO_REG") continue;
BitsInit *BI = R->getValueAsBitsInit("Inst");
const std::vector<RecordVal> &Vals = R->getValues();
CodeGenInstruction &CGI = Target.getInstruction(InstName);
// Loop over all of the fields in the instruction, determining which are the
// operands to the instruction.
unsigned op = 0;
for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
if (!Vals[i].getPrefix() && !Vals[i].getValue()->isComplete()) {
// Is the operand continuous? If so, we can just mask and OR it in
// instead of doing it bit-by-bit, saving a lot in runtime cost.
const std::string &VarName = Vals[i].getName();
bool gotOp = false;
for (int bit = BI->getNumBits()-1; bit >= 0; ) {
int varBit = getVariableBit(VarName, BI, bit);
if (varBit == -1) {
--bit;
} else {
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;
}
if (!gotOp) {
/// If this operand is not supposed to be emitted by the generated
/// emitter, skip it.
while (CGI.isFlatOperandNotEmitted(op))
++op;
Case += " // op: " + VarName + "\n"
+ " op = getMachineOpValue(MI, MI.getOperand("
+ utostr(op++) + "));\n";
gotOp = true;
}
unsigned opMask = (1 << N) - 1;
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::vector<std::string> &InstList = CaseMap[Case];
InstList.push_back(InstName);
}
// Emit initial function code
o << " const unsigned opcode = MI.getOpcode();\n"
<< " unsigned Value = InstBits[opcode];\n"
<< " unsigned op = 0;\n"
<< " op = 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 " << Namespace << InstList[i] << ":";
}
o << " {\n";
o << Case;
o << " break;\n"
<< " }\n";
}
// Default case: unhandled opcode
o << " default:\n"
<< " cerr << \"Not supported instr: \" << MI << \"\\n\";\n"
<< " abort();\n"
<< " }\n"
<< " return Value;\n"
<< "}\n\n";
}
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