[llvm] [M68k] Fix ODR violation in GISel code (PR #72797)

[Vadim Petrochenkov via llvm-commits]

https://github.com/petrochenkov updated https://github.com/llvm/llvm-project/pull/72797

>From 0f7858f17b5ee775d4a2172762ec2f207aa6a829 Mon Sep 17 00:00:00 2001
From: Vadim Petrochenkov <vadim.petrochenkov at gmail.com>
Date: Sun, 19 Nov 2023 16:08:05 +0300
Subject: [PATCH] [M68k] Fix ODR violation in GISel code

It prevents LLVM from being linked with LLD at least on Windows, with errors like this:

```
  = note: ld.lld: error: duplicate symbol: vtable for llvm::FormalArgHandler
          >>> defined at librustc_llvm-a81737dd65a7c126.rlib(M68kCallLowering.cpp.obj)
          >>> defined at librustc_llvm-a81737dd65a7c126.rlib(PPCCallLowering.cpp.obj)
```

Binutils linker also complains about this, but only with warnings.

`FormalArgHandler` has a base class `M68kIncomingValueHandler` which doesn't have a virtual method `markPhysRegUsed` like `IncomingValueHandler`s for all other targets including PPC, so it results in a conflict.
The simplest fix is to rename the `FormalArgHandler` structure (rather than to adding virtual methods for compatibility).
---
 llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp | 7 ++++++-
 llvm/lib/Target/M68k/GISel/M68kCallLowering.h   | 5 -----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp b/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
index bb63516e957fd5e..bbba485a481e356 100644
--- a/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
+++ b/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
@@ -25,6 +25,11 @@
 
 using namespace llvm;
 
+struct M68kFormalArgHandler : public M68kIncomingValueHandler {
+  M68kFormalArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI)
+      : M68kIncomingValueHandler(MIRBuilder, MRI) {}
+};
+
 M68kCallLowering::M68kCallLowering(const M68kTargetLowering &TLI)
     : CallLowering(&TLI) {}
 
@@ -119,7 +124,7 @@ bool M68kCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   CCAssignFn *AssignFn =
       TLI.getCCAssignFn(F.getCallingConv(), false, F.isVarArg());
   IncomingValueAssigner ArgAssigner(AssignFn);
-  FormalArgHandler ArgHandler(MIRBuilder, MRI);
+  M68kFormalArgHandler ArgHandler(MIRBuilder, MRI);
   return determineAndHandleAssignments(ArgHandler, ArgAssigner, SplitArgs,
                                        MIRBuilder, F.getCallingConv(),
                                        F.isVarArg());
diff --git a/llvm/lib/Target/M68k/GISel/M68kCallLowering.h b/llvm/lib/Target/M68k/GISel/M68kCallLowering.h
index 7644e6cffbb1bc1..309a2e51a3cf2c0 100644
--- a/llvm/lib/Target/M68k/GISel/M68kCallLowering.h
+++ b/llvm/lib/Target/M68k/GISel/M68kCallLowering.h
@@ -64,11 +64,6 @@ struct M68kIncomingValueHandler : public CallLowering::IncomingValueHandler {
                            ISD::ArgFlagsTy Flags) override;
 };
 
-struct FormalArgHandler : public M68kIncomingValueHandler {
-  FormalArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI)
-      : M68kIncomingValueHandler(MIRBuilder, MRI) {}
-};
-
 struct CallReturnHandler : public M68kIncomingValueHandler {
   CallReturnHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
                     MachineInstrBuilder &MIB)