[RISCV] Avoid pointer element type access for masked atomicrmw intrinsics

masked.atomicrmw.*.i32 intrinsics access an i32 (and then possibly
mask it), so hardcode MVT::i32 as the access type here, rather than
determining it from the pointer element type.

Differential Revision: https://reviews.llvm.org/D118336

Author: nikic

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -1121,17 +1121,15 @@ bool RISCVTargetLowering::getTgtMemIntrinsic(IntrinsicInfo &Info,
   case Intrinsic::riscv_masked_atomicrmw_min_i32:
   case Intrinsic::riscv_masked_atomicrmw_umax_i32:
   case Intrinsic::riscv_masked_atomicrmw_umin_i32:
-  case Intrinsic::riscv_masked_cmpxchg_i32: {
-    PointerType *PtrTy = cast<PointerType>(I.getArgOperand(0)->getType());
+  case Intrinsic::riscv_masked_cmpxchg_i32:
     Info.opc = ISD::INTRINSIC_W_CHAIN;
-    Info.memVT = MVT::getVT(PtrTy->getPointerElementType());
+    Info.memVT = MVT::i32;
     Info.ptrVal = I.getArgOperand(0);
     Info.offset = 0;
     Info.align = Align(4);
     Info.flags = MachineMemOperand::MOLoad | MachineMemOperand::MOStore |
                  MachineMemOperand::MOVolatile;
     return true;
-  }
   case Intrinsic::riscv_masked_strided_load:
     Info.opc = ISD::INTRINSIC_W_CHAIN;
     Info.ptrVal = I.getArgOperand(1);