Add deref(), add delete helper, refactor pre-alloc

pythonbpf/binary_ops.py

@@ -1,11 +1,15 @@
 import ast
 from llvmlite import ir
 
+
 def handle_binary_op(rval, module, builder, func, local_sym_tab, map_sym_tab):
+    print(module)
     left = rval.left
     right = rval.right
     op = rval.op
 
+    # In case of pointers, we'll deref once.
+
     if isinstance(left, ast.Name):
         left = local_sym_tab[left.id]
     elif isinstance(left, ast.Constant):
@@ -20,6 +24,8 @@ def handle_binary_op(rval, module, builder, func, local_sym_tab, map_sym_tab):
     else:
         SyntaxError("Unsupported right operand type")
 
+    print(f"left is {left}, right is {right}, op is {op}")
+
     if isinstance(op, ast.Add):
         result = builder.add(left, right)
     elif isinstance(op, ast.Sub):

pythonbpf/bpf_helper_handler.py

@@ -268,11 +268,67 @@ def bpf_map_update_elem_emitter(call, map_ptr, module, builder, local_sym_tab=No
     return result
 
 
+def bpf_map_delete_elem_emitter(call, map_ptr, module, builder, local_sym_tab=None):
+    """
+    Emit LLVM IR for bpf_map_delete_elem helper function call.
+    Expected call signature: map.delete(key)
+    """
+    # Check for correct number of arguments
+    if not call.args or len(call.args) != 1:
+        raise ValueError("Map delete expects exactly 1 argument (key), got "
+                         f"{len(call.args)}")
+
+    key_arg = call.args[0]
+
+    # Handle key argument
+    if isinstance(key_arg, ast.Name):
+        key_name = key_arg.id
+        if local_sym_tab and key_name in local_sym_tab:
+            key_ptr = local_sym_tab[key_name]
+        else:
+            raise ValueError(
+                f"Key variable {key_name} not found in local symbol table.")
+    elif isinstance(key_arg, ast.Constant) and isinstance(key_arg.value, int):
+        # Handle constant integer keys
+        key_val = key_arg.value
+        key_type = ir.IntType(64)
+        key_ptr = builder.alloca(key_type)
+        key_ptr.align = key_type.width // 8
+        builder.store(ir.Constant(key_type, key_val), key_ptr)
+    else:
+        raise NotImplementedError(
+            "Only simple variable names and integer constants are supported as keys in map delete.")
+
+    if key_ptr is None:
+        raise ValueError("Key pointer is None.")
+
+    # Cast map pointer to void*
+    map_void_ptr = builder.bitcast(map_ptr, ir.PointerType())
+
+    # Define function type for bpf_map_delete_elem
+    fn_type = ir.FunctionType(
+        ir.IntType(64),  # Return type: int64 (status code)
+        [ir.PointerType(), ir.PointerType()],  # Args: (void*, void*)
+        var_arg=False
+    )
+    fn_ptr_type = ir.PointerType(fn_type)
+
+    # Helper ID 3 is bpf_map_delete_elem
+    fn_addr = ir.Constant(ir.IntType(64), 3)
+    fn_ptr = builder.inttoptr(fn_addr, fn_ptr_type)
+
+    # Call the helper function
+    result = builder.call(fn_ptr, [map_void_ptr, key_ptr], tail=False)
+
+    return result
+
+
 helper_func_list = {
     "lookup": bpf_map_lookup_elem_emitter,
     "print": bpf_printk_emitter,
     "ktime": bpf_ktime_get_ns_emitter,
     "update": bpf_map_update_elem_emitter,
+    "delete": bpf_map_delete_elem_emitter,
 }
 
 

pythonbpf/expr_pass.py

@@ -25,7 +25,29 @@ def eval_expr(func, module, builder, expr, local_sym_tab, map_sym_tab):
         from .bpf_helper_handler import helper_func_list, handle_helper_call
 
         if isinstance(expr.func, ast.Name):
-            # check for helpers first
+            # check deref
+            if expr.func.id == "deref":
+                print(f"Handling deref {ast.dump(expr)}")
+                if len(expr.args) != 1:
+                    print("deref takes exactly one argument")
+                    return None
+                arg = expr.args[0]
+                if isinstance(arg, ast.Call) and isinstance(arg.func, ast.Name) and arg.func.id == "deref":
+                    print("Multiple deref not supported")
+                    return None
+                if isinstance(arg, ast.Name):
+                    if arg.id in local_sym_tab:
+                        arg = local_sym_tab[arg.id]
+                    else:
+                        print(f"Undefined variable {arg.id}")
+                        return None
+                if arg is None:
+                    print("Failed to evaluate deref argument")
+                    return None
+                val = builder.load(arg)
+                return val
+
+            # check for helpers
             if expr.func.id in helper_func_list:
                 return handle_helper_call(
                     expr, module, builder, func, local_sym_tab, map_sym_tab)

pythonbpf/functions_pass.py

@@ -79,6 +79,17 @@ def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab):
                 builder.store(val, local_sym_tab[var_name])
                 # local_sym_tab[var_name] = var
                 print(f"Assigned constant {rval.func.id} to {var_name}")
+            elif call_type == "deref" and len(rval.args) == 1:
+                print(f"Handling deref assignment {ast.dump(rval)}")
+                val = eval_expr(func, module, builder, rval,
+                                local_sym_tab, map_sym_tab)
+                if val is None:
+                    print("Failed to evaluate deref argument")
+                    return
+                print(f"Dereferenced value: {val}, storing in {var_name}")
+                builder.store(val, local_sym_tab[var_name])
+                # local_sym_tab[var_name] = var
+                print(f"Dereferenced and assigned to {var_name}")
             else:
                 print(f"Unsupported assignment call type: {call_type}")
         elif isinstance(rval.func, ast.Attribute):
@@ -227,16 +238,16 @@ def process_stmt(func, module, builder, stmt, local_sym_tab, map_sym_tab, did_re
     return did_return
 
 
-def process_func_body(module, builder, func_node, func, ret_type, map_sym_tab):
-    """Process the body of a bpf function"""
-    # TODO: A lot.  We just have print -> bpf_trace_printk for now
-    did_return = False
-
-    local_sym_tab = {}
-
-    # pre-allocate dynamic variables
-    for stmt in func_node.body:
-        if isinstance(stmt, ast.Assign):
+def allocate_mem(module, builder, body, func, ret_type, map_sym_tab, local_sym_tab):
+    for stmt in body:
+        if isinstance(stmt, ast.If):
+            if stmt.body:
+                local_sym_tab = allocate_mem(
+                    module, builder, stmt.body, func, ret_type, map_sym_tab, local_sym_tab)
+            if stmt.orelse:
+                local_sym_tab = allocate_mem(
+                    module, builder, stmt.orelse, func, ret_type, map_sym_tab, local_sym_tab)
+        elif isinstance(stmt, ast.Assign):
             if len(stmt.targets) != 1:
                 print("Unsupported multiassignment")
                 continue
@@ -262,6 +273,13 @@ def process_func_body(module, builder, func_node, func, ret_type, map_sym_tab):
                         var.align = ir_type.width // 8
                         print(
                             f"Pre-allocated variable {var_name} for helper")
+                    elif call_type == "deref" and len(rval.args) == 1:
+                        # Assume return type is int64 for now
+                        ir_type = ir.IntType(64)
+                        var = builder.alloca(ir_type, name=var_name)
+                        var.align = ir_type.width // 8
+                        print(
+                            f"Pre-allocated variable {var_name} for deref")
                 elif isinstance(rval.func, ast.Attribute):
                     ir_type = ir.PointerType(ir.IntType(64))
                     var = builder.alloca(ir_type, name=var_name)
@@ -292,6 +310,19 @@ def process_func_body(module, builder, func_node, func, ret_type, map_sym_tab):
                 print("Unsupported assignment value type")
                 continue
             local_sym_tab[var_name] = var
+    return local_sym_tab
+
+
+def process_func_body(module, builder, func_node, func, ret_type, map_sym_tab):
+    """Process the body of a bpf function"""
+    # TODO: A lot.  We just have print -> bpf_trace_printk for now
+    did_return = False
+
+    local_sym_tab = {}
+
+    # pre-allocate dynamic variables
+    local_sym_tab = allocate_mem(
+        module, builder, func_node.body, func, ret_type, map_sym_tab, local_sym_tab)
 
     print(f"Local symbol table: {local_sym_tab.keys()}")