[AArch64][GISel] Use Register instead of MCRegister for markPhysRegUsed in CallLowering.

[topperc]

For "returned" attribute arguments, the physical register is really a
virtual register which shouldn't be stored in an MCRegister. This
moves the conversion from Register to MCRegister into the derived
classes of IncomingArgHandler. The derived class ReturnedArgCallReturnHandler
does not use the register so no MCRegister is created in that case.
The function and argument have been renamed to remove "Phys".

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

Author: Craig Topper (topperc)

Changes

For "returned" attribute arguments, the physical register is really a
virtual register which shouldn't be stored in an MCRegister. This
moves the conversion from Register to MCRegister into the derived
classes of IncomingArgHandler. The derived class ReturnedArgCallReturnHandler
does not use the register so no MCRegister is created in that case.

I can remove Phys from function name for clarity if we want.

---

Full diff: https://github.com/llvm/llvm-project/pull/122853.diff

1 Files Affected:

• (modified) llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp (+4-4)

diff --git a/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp b/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
index 15f1c99e87246b..3fceb922f35520 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
@@ -207,14 +207,14 @@ struct IncomingArgHandler : public CallLowering::IncomingValueHandler {
   /// 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;
+  virtual void markPhysRegUsed(Register PhysReg) = 0;
 };
 
 struct FormalArgHandler : public IncomingArgHandler {
   FormalArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI)
       : IncomingArgHandler(MIRBuilder, MRI) {}
 
-  void markPhysRegUsed(MCRegister PhysReg) override {
+  void markPhysRegUsed(Register PhysReg) override {
     MIRBuilder.getMRI()->addLiveIn(PhysReg);
     MIRBuilder.getMBB().addLiveIn(PhysReg);
   }
@@ -225,7 +225,7 @@ struct CallReturnHandler : public IncomingArgHandler {
                     MachineInstrBuilder MIB)
       : IncomingArgHandler(MIRBuilder, MRI), MIB(MIB) {}
 
-  void markPhysRegUsed(MCRegister PhysReg) override {
+  void markPhysRegUsed(Register PhysReg) override {
     MIB.addDef(PhysReg, RegState::Implicit);
   }
 
@@ -239,7 +239,7 @@ struct ReturnedArgCallReturnHandler : public CallReturnHandler {
                                MachineInstrBuilder MIB)
       : CallReturnHandler(MIRBuilder, MRI, MIB) {}
 
-  void markPhysRegUsed(MCRegister PhysReg) override {}
+  void markPhysRegUsed(Register PhysReg) override {}
 };
 
 struct OutgoingArgHandler : public CallLowering::OutgoingValueHandler {

[arsenm]

I think the confusion here is deeper, and I'm not sure a virtual register should reach here. addLiveIn for a virtual register also doesn't make sense.

[topperc]

It's not a virtual register when FormalArgHandler::markPhysRegUsed is called. It's only virtual when ReturnedArgCallReturnHandler::markPhysRegUsed is called. This is a virtual function.

[topperc]

I've changed to use Register::asMCReg() instead of implicit conversion for the addLiveIn calls. That will check that it is safe to convert from Register to MCRegister.