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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-m68k

Author: Vadim Petrochenkov (petrochenkov)

<details>
<summary>Changes</summary>

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 add virtual methods for compatibility).

cc https://github.com/rust-lang/rust/issues/107668

---
Full diff: https://github.com/llvm/llvm-project/pull/72797.diff


2 Files Affected:

- (modified) llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp (+1-1) 
- (modified) llvm/lib/Target/M68k/GISel/M68kCallLowering.h (+2-2) 


``````````diff
diff --git a/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp b/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
index bb63516e957fd5e..8aa8a48c12d501c 100644
--- a/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
+++ b/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
@@ -119,7 +119,7 @@ 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..82b5cee9e03bcc3 100644
--- a/llvm/lib/Target/M68k/GISel/M68kCallLowering.h
+++ b/llvm/lib/Target/M68k/GISel/M68kCallLowering.h
@@ -64,8 +64,8 @@ struct M68kIncomingValueHandler : public CallLowering::IncomingValueHandler {
                            ISD::ArgFlagsTy Flags) override;
 };
 
-struct FormalArgHandler : public M68kIncomingValueHandler {
-  FormalArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI)
+struct M68kFormalArgHandler : public M68kIncomingValueHandler {
+  M68kFormalArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI)
       : M68kIncomingValueHandler(MIRBuilder, MRI) {}
 };
 

``````````

</details>


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