Let us add some local variables:<\/p>\n
\nint foo() {\r\n int retval = 0x0AB;\r\n int dummy = 0;\r\n return retval;\r\n}\r\n<\/pre>\n<\/blockquote>\nThis requires adding some information about accessing memory. I will just postulate that I have memory available from address 1 growing upwards. As anyone that really knows the HP-41 understands, this is a very bad idea. However we are still just showing some basic LLVM principles, not producing actually useful Nut code. I am however excluding the possibility of generating READ 0<\/code>, as that instruction does not even exist.<\/p>\nSome code snippets:<\/p>\n
\n \/\/ Addressing modes.\r\n def ADDR : ComplexPattern<iPTR, 2, \"SelectADDR\",\r\n [frameindex], []>;\r\n\r\n \/\/ Address operands\r\n def MEM : Operand {\r\n let MIOperandInfo = (ops RC, i16imm);\r\n let PrintMethod = \"printMemOperand\";\r\n let DecoderMethod = \"decodeMemOperand\";\r\n }\r\n \r\n ...\r\n \r\n let mayLoad=1 in {\r\n def READ : HP41MCODEInst<0x078, (outs RC:$r),\r\n (ins MEM:$addr), \"READ $addr\",\r\n [(set RC:$r, (load ADDR:$addr))]>;\r\n }\r\n\r\n let mayStore=1 in {\r\n def WRIT : HP41MCODEInst<0x068, (outs), (ins MEM:$addr,\r\n RC:$r), \"WRIT $addr\", [(store RC:$r, ADDR:$addr)]>;\r\n }\r\n\r\n ...\r\n\r\n bool\r\n HP41MCODERegisterInfo::eliminateFrameIndex(\r\n MachineBasicBlock::iterator II,\r\n int SPAdj, unsigned FIOperandNum,\r\n RegScavenger *RS) const {\r\n MachineInstr &MI = *II;\r\n int FrameIndex = MI.getOperand(FIOperandNum).getIndex();\r\n MachineFunction &MF = *MI.getParent()->getParent();\r\n const HP41MCODEFrameLowering *TFI = getFrameLowering(MF);\r\n llvm::Register FrameReg;\r\n int Offset;\r\n Offset = TFI->getFrameIndexReference(MF, FrameIndex,\r\n FrameReg).getFixed()\/4+1;\r\n MI.getOperand(FIOperandNum).ChangeToRegister(FrameReg,\r\n false);\r\n MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);\r\n return false;\r\n }\r\n\r\n ...\r\n\r\n void HP41MCODEInstPrinter::printMemOperand(const MCInst *MI,\r\n int opNum,\r\n const MCSubtargetInfo &STI,\r\n raw_ostream &O, const char *Modifier) {\r\n const MCOperand &MO = MI->getOperand(opNum+1);\r\n \r\n if (MO.isImm()) {\r\n O << format_decimal((int)MO.getImm(), 1); return; }\r\n assert(MO.isExpr() &&\r\n \"Unknown operand kind in printMemOperand\");\r\n MO.getExpr()->print(O, &MAI);\r\n }\r\n\r\n ...\r\n\r\n bool HP41MCODEDAGToDAGISel::SelectADDR(SDValue Addr,\r\n SDValue &Base, SDValue &Offset) {\r\n if (FrameIndexSDNode *FIN = dyn_cast(Addr)) {\r\n Base = CurDAG->getTargetFrameIndex(\r\n FIN->getIndex(), TLI->getPointerTy(\r\n CurDAG->getDataLayout()));\r\n Offset = CurDAG->getTargetConstant(0, SDLoc(Addr),\r\n MVT::i32);\r\n return true;\r\n }\r\n\r\n return false;\r\n }\r\n\r\n\r\n<\/pre>\n<\/blockquote>\nThen we end up with:<\/p>\n
\n\t.file\t\"hello.c\"\r\n\t.text\r\n\t.globl\tfoo ! -- Begin function foo\r\n\t.type\tfoo,@function\r\nfoo: ! @foo\r\n! %bb.0: ! %entry\r\n\tLDI S&X HEX: 0AB\r\n\tWRIT 2\r\n\tC=0 ALL\r\n\tWRIT 1\r\n\tREAD 2\r\n\tRTN\r\n.Lfunc_end0:\r\n\t.size\tfoo, .Lfunc_end0-foo\r\n ! -- End function\r\n\t.ident\t\"clang version 20.0.0git (https:\/\/github.com\/llvm\/llvm-project.git ea1dfd50bfdfbd75969fd7653bc71c81f2a2350f)\"\r\n\t.section\t\".note.GNU-stack\"\r\n\t.addrsig\r\n\r\n<\/pre>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"Let us add some local variables: int foo() { int retval = 0x0AB; int dummy = 0; return retval; } This requires adding some information about accessing memory. I will just postulate that I have memory available from address 1 growing upwards. As anyone that really knows the HP-41 understands, this is a very bad … Continue reading