CodeEmitterGen.cpp revision f8c7394781f7cf27ac52ca087e289436d36844da
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" 21using namespace llvm; 22 23void 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_SUBCLASS") 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. 64int 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 78void 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_SUBCLASS") { 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_SUBCLASS") 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} 252