6122f3e60d
branch. This brings us very close to the 3.0 release, which is expected in a week or two. MFC after: 1 week
307 lines
10 KiB
C++
307 lines
10 KiB
C++
//===- CodeEmitterGen.cpp - Code Emitter Generator ------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// CodeEmitterGen uses the descriptions of instructions and their fields to
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// construct an automated code emitter: a function that, given a MachineInstr,
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// returns the (currently, 32-bit unsigned) value of the instruction.
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//
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//===----------------------------------------------------------------------===//
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#include "CodeEmitterGen.h"
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#include "CodeGenTarget.h"
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#include "llvm/TableGen/Record.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include <map>
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using namespace llvm;
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// FIXME: Somewhat hackish to use a command line option for this. There should
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// be a CodeEmitter class in the Target.td that controls this sort of thing
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// instead.
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static cl::opt<bool>
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MCEmitter("mc-emitter",
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cl::desc("Generate CodeEmitter for use with the MC library."),
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cl::init(false));
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void CodeEmitterGen::reverseBits(std::vector<Record*> &Insts) {
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for (std::vector<Record*>::iterator I = Insts.begin(), E = Insts.end();
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I != E; ++I) {
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Record *R = *I;
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if (R->getValueAsString("Namespace") == "TargetOpcode" ||
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R->getValueAsBit("isPseudo"))
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continue;
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BitsInit *BI = R->getValueAsBitsInit("Inst");
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unsigned numBits = BI->getNumBits();
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SmallVector<Init *, 16> NewBits(numBits);
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for (unsigned bit = 0, end = numBits / 2; bit != end; ++bit) {
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unsigned bitSwapIdx = numBits - bit - 1;
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Init *OrigBit = BI->getBit(bit);
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Init *BitSwap = BI->getBit(bitSwapIdx);
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NewBits[bit] = BitSwap;
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NewBits[bitSwapIdx] = OrigBit;
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}
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if (numBits % 2) {
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unsigned middle = (numBits + 1) / 2;
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NewBits[middle] = BI->getBit(middle);
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}
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BitsInit *NewBI = BitsInit::get(NewBits);
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// Update the bits in reversed order so that emitInstrOpBits will get the
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// correct endianness.
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R->getValue("Inst")->setValue(NewBI);
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}
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}
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// If the VarBitInit at position 'bit' matches the specified variable then
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// return the variable bit position. Otherwise return -1.
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int CodeEmitterGen::getVariableBit(const std::string &VarName,
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BitsInit *BI, int bit) {
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if (VarBitInit *VBI = dynamic_cast<VarBitInit*>(BI->getBit(bit))) {
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if (VarInit *VI = dynamic_cast<VarInit*>(VBI->getVariable()))
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if (VI->getName() == VarName)
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return VBI->getBitNum();
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} else if (VarInit *VI = dynamic_cast<VarInit*>(BI->getBit(bit))) {
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if (VI->getName() == VarName)
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return 0;
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}
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return -1;
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}
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void CodeEmitterGen::
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AddCodeToMergeInOperand(Record *R, BitsInit *BI, const std::string &VarName,
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unsigned &NumberedOp,
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std::string &Case, CodeGenTarget &Target) {
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CodeGenInstruction &CGI = Target.getInstruction(R);
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// Determine if VarName actually contributes to the Inst encoding.
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int bit = BI->getNumBits()-1;
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// Scan for a bit that this contributed to.
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for (; bit >= 0; ) {
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if (getVariableBit(VarName, BI, bit) != -1)
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break;
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--bit;
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}
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// If we found no bits, ignore this value, otherwise emit the call to get the
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// operand encoding.
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if (bit < 0) return;
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// If the operand matches by name, reference according to that
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// operand number. Non-matching operands are assumed to be in
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// order.
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unsigned OpIdx;
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if (CGI.Operands.hasOperandNamed(VarName, OpIdx)) {
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// Get the machine operand number for the indicated operand.
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OpIdx = CGI.Operands[OpIdx].MIOperandNo;
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assert(!CGI.Operands.isFlatOperandNotEmitted(OpIdx) &&
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"Explicitly used operand also marked as not emitted!");
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} else {
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/// If this operand is not supposed to be emitted by the
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/// generated emitter, skip it.
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while (CGI.Operands.isFlatOperandNotEmitted(NumberedOp))
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++NumberedOp;
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OpIdx = NumberedOp++;
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}
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std::pair<unsigned, unsigned> SO = CGI.Operands.getSubOperandNumber(OpIdx);
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std::string &EncoderMethodName = CGI.Operands[SO.first].EncoderMethodName;
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// If the source operand has a custom encoder, use it. This will
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// get the encoding for all of the suboperands.
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if (!EncoderMethodName.empty()) {
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// A custom encoder has all of the information for the
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// sub-operands, if there are more than one, so only
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// query the encoder once per source operand.
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if (SO.second == 0) {
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Case += " // op: " + VarName + "\n" +
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" op = " + EncoderMethodName + "(MI, " + utostr(OpIdx);
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if (MCEmitter)
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Case += ", Fixups";
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Case += ");\n";
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}
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} else {
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Case += " // op: " + VarName + "\n" +
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" op = getMachineOpValue(MI, MI.getOperand(" + utostr(OpIdx) + ")";
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if (MCEmitter)
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Case += ", Fixups";
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Case += ");\n";
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}
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for (; bit >= 0; ) {
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int varBit = getVariableBit(VarName, BI, bit);
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// If this bit isn't from a variable, skip it.
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if (varBit == -1) {
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--bit;
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continue;
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}
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// Figure out the consecutive range of bits covered by this operand, in
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// order to generate better encoding code.
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int beginInstBit = bit;
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int beginVarBit = varBit;
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int N = 1;
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for (--bit; bit >= 0;) {
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varBit = getVariableBit(VarName, BI, bit);
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if (varBit == -1 || varBit != (beginVarBit - N)) break;
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++N;
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--bit;
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}
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unsigned opMask = ~0U >> (32-N);
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int opShift = beginVarBit - N + 1;
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opMask <<= opShift;
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opShift = beginInstBit - beginVarBit;
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if (opShift > 0) {
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Case += " Value |= (op & " + utostr(opMask) + "U) << " +
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itostr(opShift) + ";\n";
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} else if (opShift < 0) {
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Case += " Value |= (op & " + utostr(opMask) + "U) >> " +
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itostr(-opShift) + ";\n";
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} else {
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Case += " Value |= op & " + utostr(opMask) + "U;\n";
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}
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}
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}
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std::string CodeEmitterGen::getInstructionCase(Record *R,
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CodeGenTarget &Target) {
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std::string Case;
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BitsInit *BI = R->getValueAsBitsInit("Inst");
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const std::vector<RecordVal> &Vals = R->getValues();
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unsigned NumberedOp = 0;
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// Loop over all of the fields in the instruction, determining which are the
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// operands to the instruction.
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for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
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// Ignore fixed fields in the record, we're looking for values like:
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// bits<5> RST = { ?, ?, ?, ?, ? };
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if (Vals[i].getPrefix() || Vals[i].getValue()->isComplete())
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continue;
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AddCodeToMergeInOperand(R, BI, Vals[i].getName(), NumberedOp, Case, Target);
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}
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std::string PostEmitter = R->getValueAsString("PostEncoderMethod");
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if (!PostEmitter.empty())
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Case += " Value = " + PostEmitter + "(MI, Value);\n";
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return Case;
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}
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void CodeEmitterGen::run(raw_ostream &o) {
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CodeGenTarget Target(Records);
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std::vector<Record*> Insts = Records.getAllDerivedDefinitions("Instruction");
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// For little-endian instruction bit encodings, reverse the bit order
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if (Target.isLittleEndianEncoding()) reverseBits(Insts);
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EmitSourceFileHeader("Machine Code Emitter", o);
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const std::vector<const CodeGenInstruction*> &NumberedInstructions =
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Target.getInstructionsByEnumValue();
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// Emit function declaration
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o << "unsigned " << Target.getName();
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if (MCEmitter)
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o << "MCCodeEmitter::getBinaryCodeForInstr(const MCInst &MI,\n"
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<< " SmallVectorImpl<MCFixup> &Fixups) const {\n";
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else
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o << "CodeEmitter::getBinaryCodeForInstr(const MachineInstr &MI) const {\n";
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// Emit instruction base values
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o << " static const unsigned InstBits[] = {\n";
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for (std::vector<const CodeGenInstruction*>::const_iterator
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IN = NumberedInstructions.begin(),
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EN = NumberedInstructions.end();
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IN != EN; ++IN) {
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const CodeGenInstruction *CGI = *IN;
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Record *R = CGI->TheDef;
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if (R->getValueAsString("Namespace") == "TargetOpcode" ||
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R->getValueAsBit("isPseudo")) {
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o << " 0U,\n";
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continue;
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}
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BitsInit *BI = R->getValueAsBitsInit("Inst");
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// Start by filling in fixed values.
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unsigned Value = 0;
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for (unsigned i = 0, e = BI->getNumBits(); i != e; ++i) {
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if (BitInit *B = dynamic_cast<BitInit*>(BI->getBit(e-i-1)))
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Value |= B->getValue() << (e-i-1);
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}
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o << " " << Value << "U," << '\t' << "// " << R->getName() << "\n";
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}
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o << " 0U\n };\n";
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// Map to accumulate all the cases.
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std::map<std::string, std::vector<std::string> > CaseMap;
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// Construct all cases statement for each opcode
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for (std::vector<Record*>::iterator IC = Insts.begin(), EC = Insts.end();
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IC != EC; ++IC) {
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Record *R = *IC;
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if (R->getValueAsString("Namespace") == "TargetOpcode" ||
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R->getValueAsBit("isPseudo"))
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continue;
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const std::string &InstName = R->getValueAsString("Namespace") + "::"
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+ R->getName();
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std::string Case = getInstructionCase(R, Target);
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CaseMap[Case].push_back(InstName);
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}
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// Emit initial function code
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o << " const unsigned opcode = MI.getOpcode();\n"
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<< " unsigned Value = InstBits[opcode];\n"
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<< " unsigned op = 0;\n"
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<< " (void)op; // suppress warning\n"
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<< " switch (opcode) {\n";
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// Emit each case statement
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std::map<std::string, std::vector<std::string> >::iterator IE, EE;
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for (IE = CaseMap.begin(), EE = CaseMap.end(); IE != EE; ++IE) {
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const std::string &Case = IE->first;
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std::vector<std::string> &InstList = IE->second;
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for (int i = 0, N = InstList.size(); i < N; i++) {
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if (i) o << "\n";
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o << " case " << InstList[i] << ":";
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}
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o << " {\n";
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o << Case;
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o << " break;\n"
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<< " }\n";
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}
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// Default case: unhandled opcode
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o << " default:\n"
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<< " std::string msg;\n"
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<< " raw_string_ostream Msg(msg);\n"
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<< " Msg << \"Not supported instr: \" << MI;\n"
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<< " report_fatal_error(Msg.str());\n"
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<< " }\n"
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<< " return Value;\n"
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<< "}\n\n";
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}
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