[NFC][MC][ARM] Reorder decoder functions N/N (#158767)

Move `DecodeT2AddrModeImm8` and `DecodeT2Imm8` definition before its
first use and eliminate the last remaining forward declarations of
decode functions.

Work on #156560 : Reorder ARM
disassembler decode functions to eliminate forward declarations

Author: jurahul

llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp

@@ -157,12 +157,6 @@ class ARMDisassembler : public MCDisassembler {
 
 } // end anonymous namespace
 
-// Forward declare these because the autogenerated code will reference them.
-// Definitions are further down.
-static DecodeStatus DecodeT2AddrModeImm8(MCInst &Inst, unsigned Val,
-                                         uint64_t Address,
-                                         const MCDisassembler *Decoder);
-
 typedef DecodeStatus OperandDecoder(MCInst &Inst, unsigned Val,
                                     uint64_t Address,
                                     const MCDisassembler *Decoder);
@@ -3167,6 +3161,65 @@ static DecodeStatus DecodeT2LoadShift(MCInst &Inst, unsigned Insn,
   return S;
 }
 
+static DecodeStatus DecodeT2Imm8(MCInst &Inst, unsigned Val, uint64_t Address,
+                                 const MCDisassembler *Decoder) {
+  int imm = Val & 0xFF;
+  if (Val == 0)
+    imm = INT32_MIN;
+  else if (!(Val & 0x100))
+    imm *= -1;
+  Inst.addOperand(MCOperand::createImm(imm));
+
+  return MCDisassembler::Success;
+}
+
+static DecodeStatus DecodeT2AddrModeImm8(MCInst &Inst, unsigned Val,
+                                         uint64_t Address,
+                                         const MCDisassembler *Decoder) {
+  DecodeStatus S = MCDisassembler::Success;
+
+  unsigned Rn = fieldFromInstruction(Val, 9, 4);
+  unsigned imm = fieldFromInstruction(Val, 0, 9);
+
+  // Thumb stores cannot use PC as dest register.
+  switch (Inst.getOpcode()) {
+  case ARM::t2STRT:
+  case ARM::t2STRBT:
+  case ARM::t2STRHT:
+  case ARM::t2STRi8:
+  case ARM::t2STRHi8:
+  case ARM::t2STRBi8:
+    if (Rn == 15)
+      return MCDisassembler::Fail;
+    break;
+  default:
+    break;
+  }
+
+  // Some instructions always use an additive offset.
+  switch (Inst.getOpcode()) {
+    case ARM::t2LDRT:
+    case ARM::t2LDRBT:
+    case ARM::t2LDRHT:
+    case ARM::t2LDRSBT:
+    case ARM::t2LDRSHT:
+    case ARM::t2STRT:
+    case ARM::t2STRBT:
+    case ARM::t2STRHT:
+      imm |= 0x100;
+      break;
+    default:
+      break;
+  }
+
+  if (!Check(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)))
+    return MCDisassembler::Fail;
+  if (!Check(S, DecodeT2Imm8(Inst, imm, Address, Decoder)))
+    return MCDisassembler::Fail;
+
+  return S;
+}
+
 static DecodeStatus DecodeT2LoadImm8(MCInst &Inst, unsigned Insn,
                                      uint64_t Address,
                                      const MCDisassembler *Decoder) {
@@ -3476,18 +3529,6 @@ static DecodeStatus DecodeT2AddrModeImm0_1020s4(MCInst &Inst, unsigned Val,
   return S;
 }
 
-static DecodeStatus DecodeT2Imm8(MCInst &Inst, unsigned Val, uint64_t Address,
-                                 const MCDisassembler *Decoder) {
-  int imm = Val & 0xFF;
-  if (Val == 0)
-    imm = INT32_MIN;
-  else if (!(Val & 0x100))
-    imm *= -1;
-  Inst.addOperand(MCOperand::createImm(imm));
-
-  return MCDisassembler::Success;
-}
-
 template <int shift>
 static DecodeStatus DecodeT2Imm7(MCInst &Inst, unsigned Val, uint64_t Address,
                                  const MCDisassembler *Decoder) {
@@ -3503,53 +3544,6 @@ static DecodeStatus DecodeT2Imm7(MCInst &Inst, unsigned Val, uint64_t Address,
   return MCDisassembler::Success;
 }
 
-static DecodeStatus DecodeT2AddrModeImm8(MCInst &Inst, unsigned Val,
-                                         uint64_t Address,
-                                         const MCDisassembler *Decoder) {
-  DecodeStatus S = MCDisassembler::Success;
-
-  unsigned Rn = fieldFromInstruction(Val, 9, 4);
-  unsigned imm = fieldFromInstruction(Val, 0, 9);
-
-  // Thumb stores cannot use PC as dest register.
-  switch (Inst.getOpcode()) {
-  case ARM::t2STRT:
-  case ARM::t2STRBT:
-  case ARM::t2STRHT:
-  case ARM::t2STRi8:
-  case ARM::t2STRHi8:
-  case ARM::t2STRBi8:
-    if (Rn == 15)
-      return MCDisassembler::Fail;
-    break;
-  default:
-    break;
-  }
-
-  // Some instructions always use an additive offset.
-  switch (Inst.getOpcode()) {
-    case ARM::t2LDRT:
-    case ARM::t2LDRBT:
-    case ARM::t2LDRHT:
-    case ARM::t2LDRSBT:
-    case ARM::t2LDRSHT:
-    case ARM::t2STRT:
-    case ARM::t2STRBT:
-    case ARM::t2STRHT:
-      imm |= 0x100;
-      break;
-    default:
-      break;
-  }
-
-  if (!Check(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)))
-    return MCDisassembler::Fail;
-  if (!Check(S, DecodeT2Imm8(Inst, imm, Address, Decoder)))
-    return MCDisassembler::Fail;
-
-  return S;
-}
-
 template <int shift>
 static DecodeStatus DecodeTAddrModeImm7(MCInst &Inst, unsigned Val,
                                         uint64_t Address,