[NFC][MC][Lanai] Rearrange decoder functions for Lanai disassembler (#154993)

Rearrange decode functions to be before including the generated
disassembler code and eliminate forward declarations for most of them.
This is possible because `fieldFromInstruction` is now in MCDecoder.h
and not in the generated disassembler code.

Author: jurahul

llvm/lib/Target/Lanai/Disassembler/LanaiDisassembler.cpp

@@ -47,34 +47,100 @@ LLVMInitializeLanaiDisassembler() {
 LanaiDisassembler::LanaiDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
     : MCDisassembler(STI, Ctx) {}
 
-// Forward declare because the autogenerated code will reference this.
-// Definition is further down.
-static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo,
-                                           uint64_t Address,
-                                           const MCDisassembler *Decoder);
+// clang-format off
+static const unsigned GPRDecoderTable[] = {
+  Lanai::R0,  Lanai::R1,  Lanai::PC,  Lanai::R3,  Lanai::SP,  Lanai::FP,
+  Lanai::R6,  Lanai::R7,  Lanai::RV,  Lanai::R9,  Lanai::RR1, Lanai::RR2,
+  Lanai::R12, Lanai::R13, Lanai::R14, Lanai::RCA, Lanai::R16, Lanai::R17,
+  Lanai::R18, Lanai::R19, Lanai::R20, Lanai::R21, Lanai::R22, Lanai::R23,
+  Lanai::R24, Lanai::R25, Lanai::R26, Lanai::R27, Lanai::R28, Lanai::R29,
+  Lanai::R30, Lanai::R31
+};
+// clang-format on
+
+DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo,
+                                    uint64_t /*Address*/,
+                                    const MCDisassembler * /*Decoder*/) {
+  if (RegNo > 31)
+    return MCDisassembler::Fail;
+
+  unsigned Reg = GPRDecoderTable[RegNo];
+  Inst.addOperand(MCOperand::createReg(Reg));
+  return MCDisassembler::Success;
+}
 
 static DecodeStatus decodeRiMemoryValue(MCInst &Inst, unsigned Insn,
                                         uint64_t Address,
-                                        const MCDisassembler *Decoder);
+                                        const MCDisassembler *Decoder) {
+  // RI memory values encoded using 23 bits:
+  //   5 bit register, 16 bit constant
+  unsigned Register = (Insn >> 18) & 0x1f;
+  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
+  unsigned Offset = (Insn & 0xffff);
+  Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));
+
+  return MCDisassembler::Success;
+}
 
 static DecodeStatus decodeRrMemoryValue(MCInst &Inst, unsigned Insn,
                                         uint64_t Address,
-                                        const MCDisassembler *Decoder);
+                                        const MCDisassembler *Decoder) {
+  // RR memory values encoded using 20 bits:
+  //   5 bit register, 5 bit register, 2 bit PQ, 3 bit ALU operator, 5 bit JJJJJ
+  unsigned Register = (Insn >> 15) & 0x1f;
+  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
+  Register = (Insn >> 10) & 0x1f;
+  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
+
+  return MCDisassembler::Success;
+}
 
 static DecodeStatus decodeSplsValue(MCInst &Inst, unsigned Insn,
                                     uint64_t Address,
-                                    const MCDisassembler *Decoder);
+                                    const MCDisassembler *Decoder) {
+  // RI memory values encoded using 17 bits:
+  //   5 bit register, 10 bit constant
+  unsigned Register = (Insn >> 12) & 0x1f;
+  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
+  unsigned Offset = (Insn & 0x3ff);
+  Inst.addOperand(MCOperand::createImm(SignExtend32<10>(Offset)));
 
-static DecodeStatus decodeBranch(MCInst &Inst, unsigned Insn, uint64_t Address,
-                                 const MCDisassembler *Decoder);
+  return MCDisassembler::Success;
+}
 
-static DecodeStatus decodePredicateOperand(MCInst &Inst, unsigned Val,
-                                           uint64_t Address,
-                                           const MCDisassembler *Decoder);
+static bool tryAddingSymbolicOperand(int64_t Value, bool IsBranch,
+                                     uint64_t Address, uint64_t Offset,
+                                     uint64_t Width, MCInst &MI,
+                                     const MCDisassembler *Decoder) {
+  return Decoder->tryAddingSymbolicOperand(MI, Value, Address, IsBranch, Offset,
+                                           Width, /*InstSize=*/0);
+}
+
+static DecodeStatus decodeBranch(MCInst &MI, unsigned Insn, uint64_t Address,
+                                 const MCDisassembler *Decoder) {
+  if (!tryAddingSymbolicOperand(Insn + Address, false, Address, 2, 23, MI,
+                                Decoder))
+    MI.addOperand(MCOperand::createImm(Insn));
+  return MCDisassembler::Success;
+}
 
 static DecodeStatus decodeShiftImm(MCInst &Inst, unsigned Insn,
                                    uint64_t Address,
-                                   const MCDisassembler *Decoder);
+                                   const MCDisassembler *Decoder) {
+  unsigned Offset = (Insn & 0xffff);
+  Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));
+
+  return MCDisassembler::Success;
+}
+
+static DecodeStatus decodePredicateOperand(MCInst &Inst, unsigned Val,
+                                           uint64_t Address,
+                                           const MCDisassembler *Decoder) {
+  if (Val >= LPCC::UNKNOWN)
+    return MCDisassembler::Fail;
+  Inst.addOperand(MCOperand::createImm(Val));
+  return MCDisassembler::Success;
+}
 
 #include "LanaiGenDisassemblerTables.inc"
 
@@ -157,95 +223,3 @@ LanaiDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
 
   return MCDisassembler::Fail;
 }
-
-static const unsigned GPRDecoderTable[] = {
-    Lanai::R0,  Lanai::R1,  Lanai::PC,  Lanai::R3,  Lanai::SP,  Lanai::FP,
-    Lanai::R6,  Lanai::R7,  Lanai::RV,  Lanai::R9,  Lanai::RR1, Lanai::RR2,
-    Lanai::R12, Lanai::R13, Lanai::R14, Lanai::RCA, Lanai::R16, Lanai::R17,
-    Lanai::R18, Lanai::R19, Lanai::R20, Lanai::R21, Lanai::R22, Lanai::R23,
-    Lanai::R24, Lanai::R25, Lanai::R26, Lanai::R27, Lanai::R28, Lanai::R29,
-    Lanai::R30, Lanai::R31};
-
-DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, unsigned RegNo,
-                                    uint64_t /*Address*/,
-                                    const MCDisassembler * /*Decoder*/) {
-  if (RegNo > 31)
-    return MCDisassembler::Fail;
-
-  unsigned Reg = GPRDecoderTable[RegNo];
-  Inst.addOperand(MCOperand::createReg(Reg));
-  return MCDisassembler::Success;
-}
-
-static DecodeStatus decodeRiMemoryValue(MCInst &Inst, unsigned Insn,
-                                        uint64_t Address,
-                                        const MCDisassembler *Decoder) {
-  // RI memory values encoded using 23 bits:
-  //   5 bit register, 16 bit constant
-  unsigned Register = (Insn >> 18) & 0x1f;
-  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
-  unsigned Offset = (Insn & 0xffff);
-  Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));
-
-  return MCDisassembler::Success;
-}
-
-static DecodeStatus decodeRrMemoryValue(MCInst &Inst, unsigned Insn,
-                                        uint64_t Address,
-                                        const MCDisassembler *Decoder) {
-  // RR memory values encoded using 20 bits:
-  //   5 bit register, 5 bit register, 2 bit PQ, 3 bit ALU operator, 5 bit JJJJJ
-  unsigned Register = (Insn >> 15) & 0x1f;
-  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
-  Register = (Insn >> 10) & 0x1f;
-  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
-
-  return MCDisassembler::Success;
-}
-
-static DecodeStatus decodeSplsValue(MCInst &Inst, unsigned Insn,
-                                    uint64_t Address,
-                                    const MCDisassembler *Decoder) {
-  // RI memory values encoded using 17 bits:
-  //   5 bit register, 10 bit constant
-  unsigned Register = (Insn >> 12) & 0x1f;
-  Inst.addOperand(MCOperand::createReg(GPRDecoderTable[Register]));
-  unsigned Offset = (Insn & 0x3ff);
-  Inst.addOperand(MCOperand::createImm(SignExtend32<10>(Offset)));
-
-  return MCDisassembler::Success;
-}
-
-static bool tryAddingSymbolicOperand(int64_t Value, bool IsBranch,
-                                     uint64_t Address, uint64_t Offset,
-                                     uint64_t Width, MCInst &MI,
-                                     const MCDisassembler *Decoder) {
-  return Decoder->tryAddingSymbolicOperand(MI, Value, Address, IsBranch, Offset,
-                                           Width, /*InstSize=*/0);
-}
-
-static DecodeStatus decodeBranch(MCInst &MI, unsigned Insn, uint64_t Address,
-                                 const MCDisassembler *Decoder) {
-  if (!tryAddingSymbolicOperand(Insn + Address, false, Address, 2, 23, MI,
-                                Decoder))
-    MI.addOperand(MCOperand::createImm(Insn));
-  return MCDisassembler::Success;
-}
-
-static DecodeStatus decodeShiftImm(MCInst &Inst, unsigned Insn,
-                                   uint64_t Address,
-                                   const MCDisassembler *Decoder) {
-  unsigned Offset = (Insn & 0xffff);
-  Inst.addOperand(MCOperand::createImm(SignExtend32<16>(Offset)));
-
-  return MCDisassembler::Success;
-}
-
-static DecodeStatus decodePredicateOperand(MCInst &Inst, unsigned Val,
-                                           uint64_t Address,
-                                           const MCDisassembler *Decoder) {
-  if (Val >= LPCC::UNKNOWN)
-    return MCDisassembler::Fail;
-  Inst.addOperand(MCOperand::createImm(Val));
-  return MCDisassembler::Success;
-}