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//===- CodeEmitterGen.cpp - Code Emitter Generator ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and 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/Support/Debug.h"
using namespace llvm;
void CodeEmitterGen::run(std::ostream &o) {
CodeGenTarget Target;
std::vector<Record*> Insts = Records.getAllDerivedDefinitions("Instruction");
EmitSourceFileHeader("Machine Code Emitter", o);
o << "namespace llvm {\n\n";
std::string Namespace = Insts[0]->getValueAsString("Namespace") + "::";
// Emit function declaration
o << "unsigned " << Target.getName() << "CodeEmitter::"
<< "getBinaryCodeForInstr(MachineInstr &MI) {\n"
<< " unsigned Value = 0;\n"
<< " DEBUG(std::cerr << MI);\n"
<< " switch (MI.getOpcode()) {\n";
// Emit a case statement for each opcode
for (std::vector<Record*>::iterator I = Insts.begin(), E = Insts.end();
I != E; ++I) {
Record *R = *I;
o << " case " << Namespace << R->getName() << ": {\n"
<< " DEBUG(std::cerr << \"Emitting " << R->getName() << "\\n\");\n";
BitsInit *BI = R->getValueAsBitsInit("Inst");
unsigned Value = 0;
const std::vector<RecordVal> &Vals = R->getValues();
DEBUG(o << " // prefilling: ");
// Start by filling in fixed values...
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);
DEBUG(o << B->getValue());
} else {
DEBUG(o << "0");
}
}
DEBUG(o << "\n");
DEBUG(o << " // " << *R->getValue("Inst") << "\n");
o << " Value = " << Value << "U;\n\n";
// Loop over all of the fields in the instruction determining which are the
// operands to the instruction.
//
unsigned op = 0;
std::map<std::string, unsigned> OpOrder;
std::map<std::string, bool> OpContinuous;
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 BitsInit *InstInit = BI;
int beginBitInVar = -1, endBitInVar = -1;
int beginBitInInst = -1, endBitInInst = -1;
bool continuous = true;
for (int bit = InstInit->getNumBits()-1; bit >= 0; --bit) {
if (VarBitInit *VBI =
dynamic_cast<VarBitInit*>(InstInit->getBit(bit))) {
TypedInit *TI = VBI->getVariable();
if (VarInit *VI = dynamic_cast<VarInit*>(TI)) {
// only process the current variable
if (VI->getName() != Vals[i].getName())
continue;
if (beginBitInVar == -1)
beginBitInVar = VBI->getBitNum();
if (endBitInVar == -1)
endBitInVar = VBI->getBitNum();
else {
if (endBitInVar == (int)VBI->getBitNum() + 1)
endBitInVar = VBI->getBitNum();
else {
continuous = false;
break;
}
}
if (beginBitInInst == -1)
beginBitInInst = bit;
if (endBitInInst == -1)
endBitInInst = bit;
else {
if (endBitInInst == bit + 1)
endBitInInst = bit;
else {
continuous = false;
break;
}
}
// maintain same distance between bits in field and bits in
// instruction. if the relative distances stay the same
// throughout,
if (beginBitInVar - (int)VBI->getBitNum() !=
beginBitInInst - bit) {
continuous = false;
break;
}
}
}
}
// If we have found no bit in "Inst" which comes from this field, then
// this is not an operand!!
if (beginBitInInst != -1) {
o << " // op" << op << ": " << Vals[i].getName() << "\n"
<< " int64_t op" << op
<<" = getMachineOpValue(MI, MI.getOperand("<<op<<"));\n";
//<< " MachineOperand &op" << op <<" = MI.getOperand("<<op<<");\n";
OpOrder[Vals[i].getName()] = op++;
DEBUG(o << " // Var: begin = " << beginBitInVar
<< ", end = " << endBitInVar
<< "; Inst: begin = " << beginBitInInst
<< ", end = " << endBitInInst << "\n");
if (continuous) {
DEBUG(o << " // continuous: op" << OpOrder[Vals[i].getName()]
<< "\n");
// Mask off the right bits
// Low mask (ie. shift, if necessary)
assert(endBitInVar >= 0 && "Negative shift amount in masking!");
if (endBitInVar != 0) {
o << " op" << OpOrder[Vals[i].getName()]
<< " >>= " << endBitInVar << ";\n";
beginBitInVar -= endBitInVar;
endBitInVar = 0;
}
// High mask
o << " op" << OpOrder[Vals[i].getName()]
<< " &= (1<<" << beginBitInVar+1 << ") - 1;\n";
// Shift the value to the correct place (according to place in inst)
assert(endBitInInst >= 0 && "Negative shift amount!");
if (endBitInInst != 0)
o << " op" << OpOrder[Vals[i].getName()]
<< " <<= " << endBitInInst << ";\n";
// Just OR in the result
o << " Value |= op" << OpOrder[Vals[i].getName()] << ";\n";
}
// otherwise, will be taken care of in the loop below using this
// value:
OpContinuous[Vals[i].getName()] = continuous;
}
}
}
for (unsigned f = 0, e = Vals.size(); f != e; ++f) {
if (Vals[f].getPrefix()) {
BitsInit *FieldInitializer = (BitsInit*)Vals[f].getValue();
// Scan through the field looking for bit initializers of the current
// variable...
for (int i = FieldInitializer->getNumBits()-1; i >= 0; --i) {
Init *I = FieldInitializer->getBit(i);
if (BitInit *BI = dynamic_cast<BitInit*>(I)) {
DEBUG(o << " // bit init: f: " << f << ", i: " << i << "\n");
} else if (UnsetInit *UI = dynamic_cast<UnsetInit*>(I)) {
DEBUG(o << " // unset init: f: " << f << ", i: " << i << "\n");
} else if (VarBitInit *VBI = dynamic_cast<VarBitInit*>(I)) {
TypedInit *TI = VBI->getVariable();
if (VarInit *VI = dynamic_cast<VarInit*>(TI)) {
// If the bits of the field are laid out consecutively in the
// instruction, then instead of separately ORing in bits, just
// mask and shift the entire field for efficiency.
if (OpContinuous[VI->getName()]) {
// already taken care of in the loop above, thus there is no
// need to individually OR in the bits
// for debugging, output the regular version anyway, commented
DEBUG(o << " // Value |= getValueBit(op"
<< OpOrder[VI->getName()] << ", " << VBI->getBitNum()
<< ")" << " << " << i << ";\n");
} else {
o << " Value |= getValueBit(op" << OpOrder[VI->getName()]
<< ", " << VBI->getBitNum()
<< ")" << " << " << i << ";\n";
}
} else if (FieldInit *FI = dynamic_cast<FieldInit*>(TI)) {
// FIXME: implement this!
o << "FIELD INIT not implemented yet!\n";
} else {
o << "Error: UNIMPLEMENTED\n";
}
}
}
}
}
o << " break;\n"
<< " }\n";
}
o << " default:\n"
<< " std::cerr << \"Not supported instr: \" << MI << \"\\n\";\n"
<< " abort();\n"
<< " }\n"
<< " return Value;\n"
<< "}\n";
o << "} // End llvm namespace \n";
}
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