[PowerPC] Fix -Wunused-variable in PPCAsmPrinter.cpp and PPCISelDAGToDAG.cpp (NFC)

llvm-project/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp:1648:15:
error: unused variable 'InstDisp' [-Werror,-Wunused-variable]
    ptrdiff_t InstDisp = TLSVarAddress + Offset - Delta;
              ^
llvm-project/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:7624:19:
error: unused variable 'TPReg' [-Werror,-Wunused-variable]
  RegisterSDNode *TPReg = dyn_cast<RegisterSDNode>(TPRegNode.getNode());
                  ^
llvm-project/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:7625:23:
error: unused variable 'Subtarget' [-Werror,-Wunused-variable]
  const PPCSubtarget &Subtarget =
                      ^

Author: DamonFool

llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -1645,7 +1645,7 @@ const MCExpr *PPCAsmPrinter::getAdjustedLocalExecExpr(const MachineOperand &MO,
     // where Delta is a multiple of 64KB: ((FinalAddress + 32768) & ~0xFFFF).
     ptrdiff_t Delta = ((FinalAddress + 32768) & ~0xFFFF);
     // Check that the total instruction displacement fits within [-32768,32768).
-    ptrdiff_t InstDisp = TLSVarAddress + Offset - Delta;
+    [[maybe_unused]] ptrdiff_t InstDisp = TLSVarAddress + Offset - Delta;
     assert((InstDisp < 32768) ||
            (InstDisp >= -32768) &&
                "Expecting the instruction displacement for local-exec TLS "

llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp

@@ -7621,8 +7621,8 @@ static void foldADDIForLocalExecAccesses(SDNode *N, SelectionDAG *DAG) {
   // access. The first operand of InitialADDI should be the thread pointer,
   // which has been checked in isEligibleToFoldADDIForLocalExecAccesses().
   SDValue TPRegNode = InitialADDI.getOperand(0);
-  RegisterSDNode *TPReg = dyn_cast<RegisterSDNode>(TPRegNode.getNode());
-  const PPCSubtarget &Subtarget =
+  [[maybe_unused]] RegisterSDNode *TPReg = dyn_cast<RegisterSDNode>(TPRegNode.getNode());
+  [[maybe_unused]] const PPCSubtarget &Subtarget =
       DAG->getMachineFunction().getSubtarget<PPCSubtarget>();
   assert((TPReg && (TPReg->getReg() == Subtarget.getThreadPointerRegister())) &&
          "Expecting the first operand to be a thread pointer for folding addi "