371 lines
13 KiB
OCaml
371 lines
13 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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(* Create an alloca instruction in the entry block of the function. This
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* is used for mutable variables etc. *)
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let create_entry_block_alloca the_function var_name =
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let builder = builder_at context (instr_begin (entry_block the_function)) in
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build_alloca double_type var_name builder
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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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let v = try Hashtbl.find named_values name with
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| Not_found -> raise (Error "unknown variable name")
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in
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(* Load the value. *)
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build_load v name builder
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| Ast.Unary (op, operand) ->
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let operand = codegen_expr operand in
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let callee = "unary" ^ (String.make 1 op) in
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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 unary operator")
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in
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build_call callee [|operand|] "unop" builder
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| Ast.Binary (op, lhs, rhs) ->
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begin match op with
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| '=' ->
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(* Special case '=' because we don't want to emit the LHS as an
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* expression. *)
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let name =
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match lhs with
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| Ast.Variable name -> name
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| _ -> raise (Error "destination of '=' must be a variable")
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in
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(* Codegen the rhs. *)
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let val_ = codegen_expr rhs in
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(* Lookup the name. *)
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let variable = try Hashtbl.find named_values name with
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| Not_found -> raise (Error "unknown variable name")
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in
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ignore(build_store val_ variable builder);
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val_
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| _ ->
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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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| _ ->
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(* If it wasn't a builtin binary operator, it must be a user defined
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* one. Emit a call to it. *)
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let callee = "binary" ^ (String.make 1 op) in
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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 "binary operator not found!")
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in
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build_call callee [|lhs_val; rhs_val|] "binop" builder
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end
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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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(* Output this as:
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* var = alloca double
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* ...
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* start = startexpr
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* store start -> var
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* goto loop
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* loop:
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* ...
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* bodyexpr
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* ...
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* loopend:
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* step = stepexpr
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* endcond = endexpr
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*
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* curvar = load var
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* nextvar = curvar + step
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* store nextvar -> var
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* br endcond, loop, endloop
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* outloop: *)
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let the_function = block_parent (insertion_block builder) in
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(* Create an alloca for the variable in the entry block. *)
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let alloca = create_entry_block_alloca the_function var_name in
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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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(* Store the value into the alloca. *)
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ignore(build_store start_val alloca builder);
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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 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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(* 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 alloca;
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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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(* Compute the end condition. *)
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let end_cond = codegen_expr end_ in
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(* Reload, increment, and restore the alloca. This handles the case where
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* the body of the loop mutates the variable. *)
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let cur_var = build_load alloca var_name builder in
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let next_var = build_add cur_var step_val "nextvar" builder in
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ignore(build_store next_var alloca builder);
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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 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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(* 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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| Ast.Var (var_names, body) ->
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let old_bindings = ref [] in
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let the_function = block_parent (insertion_block builder) in
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(* Register all variables and emit their initializer. *)
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Array.iter (fun (var_name, init) ->
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(* Emit the initializer before adding the variable to scope, this
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* prevents the initializer from referencing the variable itself, and
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* permits stuff like this:
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* var a = 1 in
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* var a = a in ... # refers to outer 'a'. *)
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let init_val =
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match init with
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| Some init -> codegen_expr init
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(* If not specified, use 0.0. *)
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| None -> const_float double_type 0.0
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in
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let alloca = create_entry_block_alloca the_function var_name in
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ignore(build_store init_val alloca builder);
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(* Remember the old variable binding so that we can restore the binding
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* when we unrecurse. *)
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begin
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try
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let old_value = Hashtbl.find named_values var_name in
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old_bindings := (var_name, old_value) :: !old_bindings;
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with Not_found -> ()
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end;
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(* Remember this binding. *)
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Hashtbl.add named_values var_name alloca;
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) var_names;
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(* Codegen the body, now that all vars are in scope. *)
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let body_val = codegen_expr body in
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(* Pop all our variables from scope. *)
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List.iter (fun (var_name, old_value) ->
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Hashtbl.add named_values var_name old_value
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) !old_bindings;
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(* Return the body computation. *)
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body_val
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let codegen_proto = function
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| Ast.Prototype (name, args) | Ast.BinOpPrototype (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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(* Create an alloca for each argument and register the argument in the symbol
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* table so that references to it will succeed. *)
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let create_argument_allocas the_function proto =
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let args = match proto with
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| Ast.Prototype (_, args) | Ast.BinOpPrototype (_, args, _) -> args
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in
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Array.iteri (fun i ai ->
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let var_name = args.(i) in
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(* Create an alloca for this variable. *)
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let alloca = create_entry_block_alloca the_function var_name in
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(* Store the initial value into the alloca. *)
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ignore(build_store ai alloca builder);
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(* Add arguments to variable symbol table. *)
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Hashtbl.add named_values var_name alloca;
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) (params the_function)
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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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(* If this is an operator, install it. *)
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begin match proto with
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| Ast.BinOpPrototype (name, args, prec) ->
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let op = name.[String.length name - 1] in
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Hashtbl.add Parser.binop_precedence op prec;
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| _ -> ()
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end;
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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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(* Add all arguments to the symbol table and create their allocas. *)
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create_argument_allocas the_function proto;
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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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