[clang] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Matt Arsenault via llvm-commits]

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@@ -103,19 +104,27 @@ void AMDGPUABIInfo::computeInfo(CGFunctionInfo &FI) const {
   if (!getCXXABI().classifyReturnType(FI))
     FI.getReturnInfo() = classifyReturnType(FI.getReturnType());
 
+  unsigned ArgumentIndex = 0;
+  const unsigned numFixedArguments = FI.getNumRequiredArgs();
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arsenm wrote:

Can you split the clang AMDGPU ABI changes into a separate PR? The tests for this are also missing 

https://github.com/llvm/llvm-project/pull/93362