[llvm] [RISCV][GISel] Minor refactoring of RISCVCallReturnHandler and RISCVIncomingValueHandler (PR #69757)

[Philip Reames via llvm-commits]

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@@ -164,28 +164,39 @@ struct RISCVIncomingValueHandler : public CallLowering::IncomingValueHandler {
 
   void assignValueToReg(Register ValVReg, Register PhysReg,
                         CCValAssign VA) override {
-    // Copy argument received in physical register to desired VReg.
-    MIRBuilder.getMBB().addLiveIn(PhysReg);
-    MIRBuilder.buildCopy(ValVReg, PhysReg);
+    markPhysRegUsed(PhysReg);
+    IncomingValueHandler::assignValueToReg(ValVReg, PhysReg, VA);
   }
 
+  /// How the physical register gets marked varies between formal
+  /// parameters (it's a basic-block live-in), and a call instruction
+  /// (it's an implicit-def of the BL).
+  virtual void markPhysRegUsed(MCRegister PhysReg) = 0;
+
 private:
   const RISCVSubtarget &Subtarget;
 };
 
+struct RISCVFormalArgHandler : public RISCVIncomingValueHandler {
+  RISCVFormalArgHandler(MachineIRBuilder &B, MachineRegisterInfo &MRI)
+      : RISCVIncomingValueHandler(B, MRI) {}
+
+  void markPhysRegUsed(MCRegister PhysReg) override {
+    MIRBuilder.getMRI()->addLiveIn(PhysReg);
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preames wrote:

The switch to RISCVFormatArgHandler isn't quite nfc due to the addition of the getMRI()->getLiveIn line.

Not objecting, just making sure you're aware of it and it wasn't accidental.  

https://github.com/llvm/llvm-project/pull/69757