Ensure byref attribute is preserved on rewritten parameters

The byref TypeAttribute may be dropped when copying attributes to the
new function with changed parameter types (ptr -> ptr addrspace(4)).
Explicitly re-add it to ensure the AMDGPU backend knows the kernarg
contains the struct data inline, not a pointer to it.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: gbaraldi

src/gcn.jl

@@ -92,11 +92,17 @@ function rewrite_byref_addrspaces!(@nospecialize(job::CompilerJob{GCNCompilerTar
         LLVM.name!(new_arg, LLVM.name(arg))
     end
 
-    # copy parameter attributes
+    # copy parameter attributes, ensuring byref is preserved with correct type
     for (i, _) in enumerate(parameters(ft))
         for attr in collect(parameter_attributes(f, i))
             push!(parameter_attributes(new_f, i), attr)
         end
+        # explicitly re-add byref with the correct type, in case the copy
+        # dropped it due to the parameter type change
+        if byref[i]
+            llvm_typ = convert(LLVMType, byref_types[i])
+            push!(parameter_attributes(new_f, i), TypeAttribute("byref", llvm_typ))
+        end
     end
 
     # load byref arguments from addrspace(4) into local allocas