Add constant check (maybe broken) and also a globals pass

pythonbpf/globals_pass.py

@@ -0,0 +1,42 @@
+from llvmlite import ir
+import ast
+
+def emit_globals(module: ir.Module, names: list[str]):
+    """
+    Emit the @llvm.compiler.used global given a list of function/global names.
+    """
+    ptr_ty = ir.PointerType()
+    used_array_ty = ir.ArrayType(ptr_ty, len(names))
+
+    elems = []
+    for name in names:
+        # Reuse existing globals (like LICENSE), don't redeclare
+        if name in module.globals:
+            g = module.get_global(name)
+        else:
+            g = ir.GlobalValue(module, ptr_ty, name)
+
+        elems.append(g.bitcast(ptr_ty))
+
+    gv = ir.GlobalVariable(module, used_array_ty, "llvm.compiler.used")
+    gv.linkage = "appending"
+    gv.initializer = ir.Constant(used_array_ty, elems)  # type: ignore
+    gv.section = "llvm.metadata"
+
+
+def globals_processing(tree, module: ir.Module):
+    collected = ["LICENSE"]
+
+    for node in tree.body:
+        if isinstance(node, ast.FunctionDef) and len(node.decorator_list) == 1:
+            dec = node.decorator_list[0]
+            if (
+                isinstance(dec, ast.Call)
+                and isinstance(dec.func, ast.Name)
+                and len(dec.args) == 1
+                and isinstance(dec.args[0], ast.Attribute)
+                and isinstance(dec.args[0].value, ast.Name)
+            ):
+                collected.append(node.name)
+
+    emit_globals(module, collected)