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

[Craig Topper via llvm-commits]

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

Forward assignValueToReg to the base class to make the copy. Add markPhysRegUsed to contain the differences between call handling and argument handling. Introduce RISCVFormalArgHandler.

This structure matches how AArch64, AMDGPU, and X86 are structured.

>From 51b3fb4b5172bba50d64e96d6560350cd329496d Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Sun, 15 Oct 2023 17:44:01 -0700
Subject: [PATCH] [RISCV][GISel] Minor refactoring of RISCVCallReturnHandler
 and RISCVIncomingValueHandler. NFC

Forward assignValueToReg to the base class to make the copy. Add
markPhysRegUsed to contain the differences between call handling
and argument handling. Introduce RISCVFormalArgHandler.

This structure matches how AArch64, AMDGPU, and X86 are structured.
---
 .../Target/RISCV/GISel/RISCVCallLowering.cpp  | 31 +++++++++++++------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp b/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
index 01b8e77252840f5..b605f2f621d040d 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
@@ -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);
+    MIRBuilder.getMBB().addLiveIn(PhysReg);
+  }
+};
+
 struct RISCVCallReturnHandler : public RISCVIncomingValueHandler {
   RISCVCallReturnHandler(MachineIRBuilder &B, MachineRegisterInfo &MRI,
                          MachineInstrBuilder &MIB)
       : RISCVIncomingValueHandler(B, MRI), MIB(MIB) {}
 
-  MachineInstrBuilder MIB;
-
-  void assignValueToReg(Register ValVReg, Register PhysReg,
-                        CCValAssign VA) override {
-    // Copy argument received in physical register to desired VReg.
+  void markPhysRegUsed(MCRegister PhysReg) override {
     MIB.addDef(PhysReg, RegState::Implicit);
-    MIRBuilder.buildCopy(ValVReg, PhysReg);
   }
+
+  MachineInstrBuilder MIB;
 };
 
 } // namespace
@@ -312,7 +323,7 @@ bool RISCVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   RISCVIncomingValueAssigner Assigner(
       CC == CallingConv::Fast ? RISCV::CC_RISCV_FastCC : RISCV::CC_RISCV,
       /*IsRet=*/false);
-  RISCVIncomingValueHandler Handler(MIRBuilder, MF.getRegInfo());
+  RISCVFormalArgHandler Handler(MIRBuilder, MF.getRegInfo());
 
   return determineAndHandleAssignments(Handler, Assigner, SplitArgInfos,
                                        MIRBuilder, CC, F.isVarArg());