utils/TableGen/CodeEmitterGen.cpp

   1 //===- CodeEmitterGen.cpp - Code Emitter Generator ------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // CodeEmitterGen uses the descriptions of instructions and their fields to
  11 // construct an automated code emitter: a function that, given a MachineInstr,
  12 // returns the (currently, 32-bit unsigned) value of the instruction.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "CodeEmitterGen.h"
  17 #include "CodeGenTarget.h"
  18 #include "Record.h"
  19 #include "llvm/ADT/StringExtras.h"
  20 #include "llvm/Support/Debug.h"
  21 using namespace llvm;
  22
  23 void CodeEmitterGen::reverseBits(std::vector<Record*> &Insts) {
  24   for (std::vector<Record*>::iterator I = Insts.begin(), E = Insts.end();
  25        I != E; ++I) {
  26     Record *R = *I;
  27     if (R->getName() == "PHI" ||
  28         R->getName() == "INLINEASM" ||
  29         R->getName() == "DBG_LABEL" ||
  30         R->getName() == "EH_LABEL" ||
  31         R->getName() == "GC_LABEL" ||
  32         R->getName() == "DECLARE" ||
  33         R->getName() == "EXTRACT_SUBREG" ||
  34         R->getName() == "INSERT_SUBREG" ||
  35         R->getName() == "IMPLICIT_DEF" ||
  36         R->getName() == "SUBREG_TO_REG" ||
  37         R->getName() == "COPY_TO_REGCLASS") continue;
  38
  39     BitsInit *BI = R->getValueAsBitsInit("Inst");
  40
  41     unsigned numBits = BI->getNumBits();
  42     BitsInit *NewBI = new BitsInit(numBits);
  43     for (unsigned bit = 0, end = numBits / 2; bit != end; ++bit) {
  44       unsigned bitSwapIdx = numBits - bit - 1;
  45       Init *OrigBit = BI->getBit(bit);
  46       Init *BitSwap = BI->getBit(bitSwapIdx);
  47       NewBI->setBit(bit, BitSwap);
  48       NewBI->setBit(bitSwapIdx, OrigBit);
  49     }
  50     if (numBits % 2) {
  51       unsigned middle = (numBits + 1) / 2;
  52       NewBI->setBit(middle, BI->getBit(middle));
  53     }
  54
  55     // Update the bits in reversed order so that emitInstrOpBits will get the
  56     // correct endianness.
  57     R->getValue("Inst")->setValue(NewBI);
  58   }
  59 }
  60
  61
  62 // If the VarBitInit at position 'bit' matches the specified variable then
  63 // return the variable bit position.  Otherwise return -1.
  64 int CodeEmitterGen::getVariableBit(const std::string &VarName,
  65             BitsInit *BI, int bit) {
  66   if (VarBitInit *VBI = dynamic_cast<VarBitInit*>(BI->getBit(bit))) {
  67     TypedInit *TI = VBI->getVariable();
  68
  69     if (VarInit *VI = dynamic_cast<VarInit*>(TI)) {
  70       if (VI->getName() == VarName) return VBI->getBitNum();
  71     }
  72   }
  73
  74   return -1;
  75 }
  76
  77
  78 void CodeEmitterGen::run(std::ostream &o) {
  79   CodeGenTarget Target;
  80   std::vector<Record*> Insts = Records.getAllDerivedDefinitions("Instruction");
  81
  82   // For little-endian instruction bit encodings, reverse the bit order
  83   if (Target.isLittleEndianEncoding()) reverseBits(Insts);
  84
  85   EmitSourceFileHeader("Machine Code Emitter", o);
  86   std::string Namespace = Insts[0]->getValueAsString("Namespace") + "::";
  87
  88   std::vector<const CodeGenInstruction*> NumberedInstructions;
  89   Target.getInstructionsByEnumValue(NumberedInstructions);
  90
  91   // Emit function declaration
  92   o << "unsigned " << Target.getName() << "CodeEmitter::"
  93     << "getBinaryCodeForInstr(const MachineInstr &MI) {\n";
  94
  95   // Emit instruction base values
  96   o << "  static const unsigned InstBits[] = {\n";
  97   for (std::vector<const CodeGenInstruction*>::iterator
  98           IN = NumberedInstructions.begin(),
  99           EN = NumberedInstructions.end();
 100        IN != EN; ++IN) {
 101     const CodeGenInstruction *CGI = *IN;
 102     Record *R = CGI->TheDef;
 103
 104     if (R->getName() == "PHI" ||
 105         R->getName() == "INLINEASM" ||
 106         R->getName() == "DBG_LABEL" ||
 107         R->getName() == "EH_LABEL" ||
 108         R->getName() == "GC_LABEL" ||
 109         R->getName() == "DECLARE" ||
 110         R->getName() == "EXTRACT_SUBREG" ||
 111         R->getName() == "INSERT_SUBREG" ||
 112         R->getName() == "IMPLICIT_DEF" ||
 113         R->getName() == "SUBREG_TO_REG" ||
 114         R->getName() == "COPY_TO_REGCLASS") {
 115       o << "    0U,\n";
 116       continue;
 117     }
 118
 119     BitsInit *BI = R->getValueAsBitsInit("Inst");
 120
 121     // Start by filling in fixed values...
 122     unsigned Value = 0;
 123     for (unsigned i = 0, e = BI->getNumBits(); i != e; ++i) {
 124       if (BitInit *B = dynamic_cast<BitInit*>(BI->getBit(e-i-1))) {
 125         Value |= B->getValue() << (e-i-1);
 126       }
 127     }
 128     o << "    " << Value << "U," << '\t' << "// " << R->getName() << "\n";
 129   }
 130   o << "    0U\n  };\n";
 131
 132   // Map to accumulate all the cases.
 133   std::map<std::string, std::vector<std::string> > CaseMap;
 134
 135   // Construct all cases statement for each opcode
 136   for (std::vector<Record*>::iterator IC = Insts.begin(), EC = Insts.end();
 137         IC != EC; ++IC) {
 138     Record *R = *IC;
 139     const std::string &InstName = R->getName();
 140     std::string Case("");
 141
 142     if (InstName == "PHI" ||
 143         InstName == "INLINEASM" ||
 144         InstName == "DBG_LABEL"||
 145         InstName == "EH_LABEL"||
 146         InstName == "GC_LABEL"||
 147         InstName == "DECLARE"||
 148         InstName == "EXTRACT_SUBREG" ||
 149         InstName == "INSERT_SUBREG" ||
 150         InstName == "IMPLICIT_DEF" ||
 151         InstName == "SUBREG_TO_REG" ||
 152         InstName == "COPY_TO_REGCLASS") continue;
 153
 154     BitsInit *BI = R->getValueAsBitsInit("Inst");
 155     const std::vector<RecordVal> &Vals = R->getValues();
 156     CodeGenInstruction &CGI = Target.getInstruction(InstName);
 157
 158     // Loop over all of the fields in the instruction, determining which are the
 159     // operands to the instruction.
 160     unsigned op = 0;
 161     for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
 162       if (!Vals[i].getPrefix() && !Vals[i].getValue()->isComplete()) {
 163         // Is the operand continuous? If so, we can just mask and OR it in
 164         // instead of doing it bit-by-bit, saving a lot in runtime cost.
 165         const std::string &VarName = Vals[i].getName();
 166         bool gotOp = false;
 167
 168         for (int bit = BI->getNumBits()-1; bit >= 0; ) {
 169           int varBit = getVariableBit(VarName, BI, bit);
 170
 171           if (varBit == -1) {
 172             --bit;
 173           } else {
 174             int beginInstBit = bit;
 175             int beginVarBit = varBit;
 176             int N = 1;
 177
 178             for (--bit; bit >= 0;) {
 179               varBit = getVariableBit(VarName, BI, bit);
 180               if (varBit == -1 || varBit != (beginVarBit - N)) break;
 181               ++N;
 182               --bit;
 183             }
 184
 185             if (!gotOp) {
 186               /// If this operand is not supposed to be emitted by the generated
 187               /// emitter, skip it.
 188               while (CGI.isFlatOperandNotEmitted(op))
 189                 ++op;
 190
 191               Case += "      // op: " + VarName + "\n"
 192                    +  "      op = getMachineOpValue(MI, MI.getOperand("
 193                    +  utostr(op++) + "));\n";
 194               gotOp = true;
 195             }
 196
 197             unsigned opMask = ~0U >> (32-N);
 198             int opShift = beginVarBit - N + 1;
 199             opMask <<= opShift;
 200             opShift = beginInstBit - beginVarBit;
 201
 202             if (opShift > 0) {
 203               Case += "      Value |= (op & " + utostr(opMask) + "U) << "
 204                    +  itostr(opShift) + ";\n";
 205             } else if (opShift < 0) {
 206               Case += "      Value |= (op & " + utostr(opMask) + "U) >> "
 207                    +  itostr(-opShift) + ";\n";
 208             } else {
 209               Case += "      Value |= op & " + utostr(opMask) + "U;\n";
 210             }
 211           }
 212         }
 213       }
 214     }
 215
 216     std::vector<std::string> &InstList = CaseMap[Case];
 217     InstList.push_back(InstName);
 218   }
 219
 220
 221   // Emit initial function code
 222   o << "  const unsigned opcode = MI.getOpcode();\n"
 223     << "  unsigned Value = InstBits[opcode];\n"
 224     << "  unsigned op = 0;\n"
 225     << "  op = op;  // suppress warning\n"
 226     << "  switch (opcode) {\n";
 227
 228   // Emit each case statement
 229   std::map<std::string, std::vector<std::string> >::iterator IE, EE;
 230   for (IE = CaseMap.begin(), EE = CaseMap.end(); IE != EE; ++IE) {
 231     const std::string &Case = IE->first;
 232     std::vector<std::string> &InstList = IE->second;
 233
 234     for (int i = 0, N = InstList.size(); i < N; i++) {
 235       if (i) o << "\n";
 236       o << "    case " << Namespace << InstList[i]  << ":";
 237     }
 238     o << " {\n";
 239     o << Case;
 240     o << "      break;\n"
 241       << "    }\n";
 242   }
 243
 244   // Default case: unhandled opcode
 245   o << "  default:\n"
 246     << "    cerr << \"Not supported instr: \" << MI << \"\\n\";\n"
 247     << "    abort();\n"
 248     << "  }\n"
 249     << "  return Value;\n"
 250     << "}\n\n";
 251 }