[RISCV] Use f64 for LocVT for ilp32 when whole f64 is passed on the stack. NFC (#69118)

This removes the special case from unpackF64OnRV32DSoftABI. We can use
the default MemLoc handling.

This also allows us to remove a isRegLoc() check from LowerCall.

This part of preparation for supporting FP arguments with GISel.

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -16452,13 +16452,13 @@ bool RISCV::CC_RISCV(const DataLayout &DL, RISCVABI::ABI ABI, unsigned ValNo,
     // stack. LowerCall/LowerFormalArguments/LowerReturn must recognise these
     // cases.
     Register Reg = State.AllocateReg(ArgGPRs);
-    LocVT = MVT::i32;
     if (!Reg) {
       unsigned StackOffset = State.AllocateStack(8, Align(8));
       State.addLoc(
           CCValAssign::getMem(ValNo, ValVT, StackOffset, LocVT, LocInfo));
       return false;
     }
+    LocVT = MVT::i32;
     if (!State.AllocateReg(ArgGPRs))
       State.AllocateStack(4, Align(4));
     State.addLoc(CCValAssign::getReg(ValNo, ValVT, Reg, LocVT, LocInfo));
@@ -16777,15 +16777,6 @@ static SDValue unpackF64OnRV32DSoftABI(SelectionDAG &DAG, SDValue Chain,
   MachineFrameInfo &MFI = MF.getFrameInfo();
   MachineRegisterInfo &RegInfo = MF.getRegInfo();
 
-  if (VA.isMemLoc()) {
-    // f64 is passed on the stack.
-    int FI =
-        MFI.CreateFixedObject(8, VA.getLocMemOffset(), /*IsImmutable=*/true);
-    SDValue FIN = DAG.getFrameIndex(FI, MVT::i32);
-    return DAG.getLoad(MVT::f64, DL, Chain, FIN,
-                       MachinePointerInfo::getFixedStack(MF, FI));
-  }
-
   assert(VA.isRegLoc() && "Expected register VA assignment");
 
   Register LoVReg = RegInfo.createVirtualRegister(&RISCV::GPRRegClass);
@@ -17298,9 +17289,8 @@ SDValue RISCVTargetLowering::LowerCall(CallLoweringInfo &CLI,
     ISD::ArgFlagsTy Flags = Outs[i].Flags;
 
     // Handle passing f64 on RV32D with a soft float ABI as a special case.
-    bool IsF64OnRV32DSoftABI =
-        VA.getLocVT() == MVT::i32 && VA.getValVT() == MVT::f64;
-    if (IsF64OnRV32DSoftABI && VA.isRegLoc()) {
+    if (VA.getLocVT() == MVT::i32 && VA.getValVT() == MVT::f64) {
+      assert(VA.isRegLoc() && "Expected register VA assignment");
       SDValue SplitF64 = DAG.getNode(
           RISCVISD::SplitF64, DL, DAG.getVTList(MVT::i32, MVT::i32), ArgValue);
       SDValue Lo = SplitF64.getValue(0);
@@ -17326,9 +17316,6 @@ SDValue RISCVTargetLowering::LowerCall(CallLoweringInfo &CLI,
       continue;
     }
 
-    // IsF64OnRV32DSoftABI && VA.isMemLoc() is handled below in the same way
-    // as any other MemLoc.
-
     // Promote the value if needed.
     // For now, only handle fully promoted and indirect arguments.
     if (VA.getLocInfo() == CCValAssign::Indirect) {