(*===----------------------------------------------------------------------=== * Code Generation *===----------------------------------------------------------------------===*) open Llvm exception Error of string let context = global_context () let the_module = create_module context "my cool jit" let builder = builder context let named_values:(string, llvalue) Hashtbl.t = Hashtbl.create 10 let double_type = double_type context let rec codegen_expr = function | Ast.Number n -> const_float double_type n | Ast.Variable name -> (try Hashtbl.find named_values name with | Not_found -> raise (Error "unknown variable name")) | Ast.Binary (op, lhs, rhs) -> let lhs_val = codegen_expr lhs in let rhs_val = codegen_expr rhs in begin match op with | '+' -> build_fadd lhs_val rhs_val "addtmp" builder | '-' -> build_fsub lhs_val rhs_val "subtmp" builder | '*' -> build_fmul lhs_val rhs_val "multmp" builder | '<' -> (* Convert bool 0/1 to double 0.0 or 1.0 *) let i = build_fcmp Fcmp.Ult lhs_val rhs_val "cmptmp" builder in build_uitofp i double_type "booltmp" builder | _ -> raise (Error "invalid binary operator") end | Ast.Call (callee, args) -> (* Look up the name in the module table. *) let callee = match lookup_function callee the_module with | Some callee -> callee | None -> raise (Error "unknown function referenced") in let params = params callee in (* If argument mismatch error. *) if Array.length params == Array.length args then () else raise (Error "incorrect # arguments passed"); let args = Array.map codegen_expr args in build_call callee args "calltmp" builder | Ast.If (cond, then_, else_) -> let cond = codegen_expr cond in (* Convert condition to a bool by comparing equal to 0.0 *) let zero = const_float double_type 0.0 in let cond_val = build_fcmp Fcmp.One cond zero "ifcond" builder in (* Grab the first block so that we might later add the conditional branch * to it at the end of the function. *) let start_bb = insertion_block builder in let the_function = block_parent start_bb in let then_bb = append_block context "then" the_function in (* Emit 'then' value. *) position_at_end then_bb builder; let then_val = codegen_expr then_ in (* Codegen of 'then' can change the current block, update then_bb for the * phi. We create a new name because one is used for the phi node, and the * other is used for the conditional branch. *) let new_then_bb = insertion_block builder in (* Emit 'else' value. *) let else_bb = append_block context "else" the_function in position_at_end else_bb builder; let else_val = codegen_expr else_ in (* Codegen of 'else' can change the current block, update else_bb for the * phi. *) let new_else_bb = insertion_block builder in (* Emit merge block. *) let merge_bb = append_block context "ifcont" the_function in position_at_end merge_bb builder; let incoming = [(then_val, new_then_bb); (else_val, new_else_bb)] in let phi = build_phi incoming "iftmp" builder in (* Return to the start block to add the conditional branch. *) position_at_end start_bb builder; ignore (build_cond_br cond_val then_bb else_bb builder); (* Set a unconditional branch at the end of the 'then' block and the * 'else' block to the 'merge' block. *) position_at_end new_then_bb builder; ignore (build_br merge_bb builder); position_at_end new_else_bb builder; ignore (build_br merge_bb builder); (* Finally, set the builder to the end of the merge block. *) position_at_end merge_bb builder; phi | Ast.For (var_name, start, end_, step, body) -> (* Emit the start code first, without 'variable' in scope. *) let start_val = codegen_expr start in (* Make the new basic block for the loop header, inserting after current * block. *) let preheader_bb = insertion_block builder in let the_function = block_parent preheader_bb in let loop_bb = append_block context "loop" the_function in (* Insert an explicit fall through from the current block to the * loop_bb. *) ignore (build_br loop_bb builder); (* Start insertion in loop_bb. *) position_at_end loop_bb builder; (* Start the PHI node with an entry for start. *) let variable = build_phi [(start_val, preheader_bb)] var_name builder in (* Within the loop, the variable is defined equal to the PHI node. If it * shadows an existing variable, we have to restore it, so save it * now. *) let old_val = try Some (Hashtbl.find named_values var_name) with Not_found -> None in Hashtbl.add named_values var_name variable; (* Emit the body of the loop. This, like any other expr, can change the * current BB. Note that we ignore the value computed by the body, but * don't allow an error *) ignore (codegen_expr body); (* Emit the step value. *) let step_val = match step with | Some step -> codegen_expr step (* If not specified, use 1.0. *) | None -> const_float double_type 1.0 in let next_var = build_add variable step_val "nextvar" builder in (* Compute the end condition. *) let end_cond = codegen_expr end_ in (* Convert condition to a bool by comparing equal to 0.0. *) let zero = const_float double_type 0.0 in let end_cond = build_fcmp Fcmp.One end_cond zero "loopcond" builder in (* Create the "after loop" block and insert it. *) let loop_end_bb = insertion_block builder in let after_bb = append_block context "afterloop" the_function in (* Insert the conditional branch into the end of loop_end_bb. *) ignore (build_cond_br end_cond loop_bb after_bb builder); (* Any new code will be inserted in after_bb. *) position_at_end after_bb builder; (* Add a new entry to the PHI node for the backedge. *) add_incoming (next_var, loop_end_bb) variable; (* Restore the unshadowed variable. *) begin match old_val with | Some old_val -> Hashtbl.add named_values var_name old_val | None -> () end; (* for expr always returns 0.0. *) const_null double_type let codegen_proto = function | Ast.Prototype (name, args) -> (* Make the function type: double(double,double) etc. *) let doubles = Array.make (Array.length args) double_type in let ft = function_type double_type doubles in let f = match lookup_function name the_module with | None -> declare_function name ft the_module (* If 'f' conflicted, there was already something named 'name'. If it * has a body, don't allow redefinition or reextern. *) | Some f -> (* If 'f' already has a body, reject this. *) if block_begin f <> At_end f then raise (Error "redefinition of function"); (* If 'f' took a different number of arguments, reject. *) if element_type (type_of f) <> ft then raise (Error "redefinition of function with different # args"); f in (* Set names for all arguments. *) Array.iteri (fun i a -> let n = args.(i) in set_value_name n a; Hashtbl.add named_values n a; ) (params f); f let codegen_func the_fpm = function | Ast.Function (proto, body) -> Hashtbl.clear named_values; let the_function = codegen_proto proto in (* Create a new basic block to start insertion into. *) let bb = append_block context "entry" the_function in position_at_end bb builder; try let ret_val = codegen_expr body in (* Finish off the function. *) let _ = build_ret ret_val builder in (* Validate the generated code, checking for consistency. *) Llvm_analysis.assert_valid_function the_function; (* Optimize the function. *) let _ = PassManager.run_function the_function the_fpm in the_function with e -> delete_function the_function; raise e