[AArch64] Simplify some TRI/TII getters. NFC.

We don't need static_casts when we use the right Subtarget.

llvm-svn: 255836
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index c5b7d0c..69b2772 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -280,9 +280,9 @@
   MachineBasicBlock::iterator MBBI = MBB.begin();
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   const Function *Fn = MF.getFunction();
-  const AArch64RegisterInfo *RegInfo = static_cast<const AArch64RegisterInfo *>(
-      MF.getSubtarget().getRegisterInfo());
-  const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
+  const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
+  const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
+  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
   MachineModuleInfo &MMI = MF.getMMI();
   AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
   bool needsFrameMoves = MMI.hasDebugInfo() || Fn->needsUnwindTableEntry();
@@ -538,10 +538,9 @@
                                         MachineBasicBlock &MBB) const {
   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
   MachineFrameInfo *MFI = MF.getFrameInfo();
-  const AArch64InstrInfo *TII =
-      static_cast<const AArch64InstrInfo *>(MF.getSubtarget().getInstrInfo());
-  const AArch64RegisterInfo *RegInfo = static_cast<const AArch64RegisterInfo *>(
-      MF.getSubtarget().getRegisterInfo());
+  const AArch64Subtarget &Subtarget = MF.getSubtarget<AArch64Subtarget>();
+  const AArch64RegisterInfo *RegInfo = Subtarget.getRegisterInfo();
+  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
   DebugLoc DL;
   bool IsTailCallReturn = false;
   if (MBB.end() != MBBI) {