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