Support named local variables and parameters

boot/stage12.elna

@@ -4,6 +4,9 @@
 
 (* Stage 12 compiler. *)
 
+(* - Local variables and parameters are saved in a local symbol table. *)
+(* - Local variables and parameters can be referenced by their name in the symbol table. *)
+
 const
 	symbol_builtin_name_int := "Int";
 	symbol_builtin_name_word := "Word";
@@ -26,6 +29,7 @@ const
 
 	(* INFO_TYPE = 1 *)
 	(* INFO_PARAMETER = 2 *)
+	(* INFO_TEMPORARY = 3 *)
 
 	(* Type info has the type it belongs to. *)
 	symbol_type_info_int := S(1, @symbol_builtin_type_int);
@@ -722,11 +726,25 @@ end;
 
 proc _compile_designator();
 begin
+	v0 := _read_token();
+	v4 := _symbol_table_lookup(@symbol_table_local, source_code_position, v0);
+
+	if v4 <> 0 then
+		_write_z("\taddi t0, sp, \0");
+		v8 := _parameter_info_get_offset(v4);
+		_write_i(v8);
+		_write_c('\n');
+		_advance_token(v0);
+
+		goto .compile_designator_end;
+	end;
 	if _load_byte(source_code_position) = 'v' then
 		_compile_local_designator();
-	else
+		goto .compile_designator_end;
-		_compile_global_designator();
 	end;
+	_compile_global_designator();
+
+.compile_designator_end:
 end;
 
 proc _compile_assignment();
@@ -834,15 +852,15 @@ begin
 		_compile_call();
 		goto .compile_statement_semicolon;
 	end;
-	if v0 = 'g' then
+	if _memcmp(source_code_position, "goto ", 5) = 0 then
 		_compile_goto();
 		goto .compile_statement_semicolon;
 	end;
-	if v0 = 'i' then
+	if _memcmp(source_code_position, "if ", 3) = 0 then
 		_compile_if();
 		goto .compile_statement_semicolon;
 	end;
-	if v0 = 'r' then
+	if _memcmp(source_code_position, "return ", 7) = 0 then
 		_compile_return_statement();
 		_write_c('\n');
 
@@ -891,6 +909,15 @@ begin
 	_write_c(v84);
 end;
 
+proc _skip_spaces();
+begin
+	v0 := _load_byte(source_code_position);
+	if v0 = '\t' then
+		_advance_token(1);
+		_skip_spaces();
+	end;
+end;
+
 proc _read_type_expression();
 begin
 	v0 := _read_token();
@@ -900,13 +927,58 @@ end;
 (* Parameters: *)
 
 (* a0 - Parameter index. *)
-proc _create_parameter_info(v88: Word);
+proc _parameter_info_create(v88: Word);
 begin
+	v8 := memory_free_pointer;
+	v4 := v8;
+	(* 2 is INFO_PARAMETER *)
+	_store_word(2, v4);
+
+	v4 := v4 + 4;
+
 	(* Calculate the stack offset: 88 - (4 * parameter_counter) *)
 	v0 := v88 * 4;
 	v0 := 88 + -v0;
+	_store_word(v0, v4);
 
-	return v0
+	v4 := v4 + 4;
+	_store_word(v4, @memory_free_pointer);
+
+	return v8
+end;
+
+proc _parameter_info_get_offset(v88: Word);
+begin
+	v88 := v88 + 4;
+	return _load_word(v88)
+end;
+
+(* Parameters: *)
+
+(* a0 - Parameter index. *)
+proc _temporary_info_create(v88: Word);
+begin
+	v8 := memory_free_pointer;
+	v4 := v8;
+	(* 3 is INFO_TEMPORARY *)
+	_store_word(3, v4);
+
+	v4 := v4 + 4;
+
+	(* Calculate the stack offset: 4 * variable_counter. *)
+	v0 := v88 * 4;
+	_store_word(v0, v4);
+
+	v4 := v4 + 4;
+	_store_word(v4, @memory_free_pointer);
+
+	return v8
+end;
+
+proc _temporary_info_get_offset(v88: Word);
+begin
+	v88 := v88 + 4;
+	return _load_word(v88)
 end;
 
 (* Parameters: *)
@@ -915,6 +987,7 @@ end;
 proc _read_procedure_parameter(v88: Word);
 begin
 	(* Read the parameter name. *)
+	v8 := source_code_position;
 	v0 := _read_token();
 	_advance_token(v0);
 
@@ -927,8 +1000,10 @@ begin
 	_write_i(v88);
 	_write_z(", \0");
 
-	(* Calculate the stack offset: 88 - (4 * parameter_counter) *)
+	v4 := _parameter_info_create(v88);
-	v4 := _create_parameter_info(v88);
+	_symbol_table_enter(@symbol_table_local, v8, v0, v4);
+
+	v4 := _parameter_info_get_offset(v4);
 	_write_i(v4);
 
 	_write_z("(sp)\n\0");
@@ -954,10 +1029,52 @@ begin
 	_advance_token(1);
 end;
 
+(* Parameters: *)
+(* a0 - Variable index. *)
+proc _read_procedure_temporary(v88: Word);
+begin
+	_skip_spaces();
+	v8 := source_code_position;
+
+	(* Read and skip variable name, colon and the space *)
+	v0 := _read_token();
+	_advance_token(v0 + 2);
+
+	_read_type_expression();
+
+	v4 := _temporary_info_create(v88);
+	_symbol_table_enter(@symbol_table_local, v8, v0, v4);
+
+	(* Skip semicolon and newline after the variable declaration *)
+	_advance_token(2);
+end;
+
+proc _read_procedure_temporaries();
+begin
+	if _memcmp(source_code_position, "var", 3) <> 0 then
+		goto .read_local_variables_end;
+	end;
+	_advance_token(4);
+	v0 := 0;
+
+.read_local_variables_loop:
+	if _memcmp(source_code_position, "begin", 5) = 0 then
+		goto .read_local_variables_end;
+	end;
+	_read_procedure_temporary(v0);
+
+	v0 := v0 + 1;
+	goto .read_local_variables_loop;
+
+.read_local_variables_end:
+end;
+
 proc _compile_procedure();
 begin
 	(* Skip "proc ". *)
 	_advance_token(5);
+	(* Clear local symbol table. *)
+	_store_word(0, @symbol_table_local);
 
 	(* Save the procedure name length. *)
 	v0 := _read_token();
@@ -977,8 +1094,12 @@ begin
 	_write_z("\taddi sp, sp, -128\n\tsw ra, 124(sp)\n\tsw s0, 120(sp)\n\taddi s0, sp, 128\n\0");
 	_read_procedure_parameters();
 
+	(* Skip semicolon and newline. *)
+	_advance_token(2);
+	_read_procedure_temporaries();
+
 	(* Skip semicolon, "begin" and newline. *)
-	_advance_token(8);
+	_advance_token(6);
 
 	_compile_procedure_body();
 
@@ -989,15 +1110,6 @@ begin
 	_advance_token(5);
 end;
 
-proc _skip_spaces();
-begin
-	v0 := _load_byte(source_code_position);
-	if v0 = '\t' then
-		_advance_token(1);
-		_skip_spaces();
-	end;
-end;
-
 (* Prints and skips a line. *)
 proc _skip_comment();
 begin
@@ -1277,37 +1389,93 @@ begin
 	_syscall(0, 0, 0, 0, 0, 0, 93);
 end;
 
+(* Looks for a symbol in the given symbol table. *)
+
+(* Parameters: *)
+(* a0 - Symbol table. *)
+(* a1 - Symbol name pointer. *)
+(* a2 - Symbol name length. *)
+
+(* Returns the symbol pointer or 0 in a0. *)
+proc _symbol_table_lookup(v88: Word, v84: Word, v80: Word);
+begin
+	v0 := 0;
+
+	(* The first word in the symbol table is its length, get it. *)
+	v4 := _load_word(v88);
+
+	(* Go to the first symbol position. *)
+	v88 := v88 + 4;
+
+	.symbol_table_lookup_loop;
+	if v4 = 0 then
+		goto .symbol_table_lookup_end;
+	end;
+
+	(* Symbol name pointer and length. *)
+	v8 := _load_word(v88);
+	v12 := _load_word(v88 + 4);
+
+	(* If lengths don't match, exit and return nil. *)
+	if v80 <> v12 then
+		goto .symbol_table_lookup_repeat;
+	end;
+	(* If names don't match, exit and return nil. *)
+	if _memcmp(v84, v8, v80) <> 0 then
+		goto .symbol_table_lookup_repeat;
+	end;
+	(* Otherwise, the symbol is found. *)
+	v0 := _load_word(v88 + 8);
+	goto .symbol_table_lookup_end;
+
+	.symbol_table_lookup_repeat;
+	v88 := v88 + 12;
+	v4 := v4 + -1;
+	goto .symbol_table_lookup_loop;
+
+	.symbol_table_lookup_end;
+	return v0
+end;
+
 (* Inserts a symbol into the table. *)
 
 (* Parameters: *)
-(* a0 - Symbol pointer. *)
+(* a0 - Symbol table. *)
-(* a1 - Symbol name length. *)
+(* a1 - Symbol name pointer. *)
-(* a2 - Symbol name pointer. *)
+(* a2 - Symbol name length. *)
-(* a3 - Symbol table. *)
+(* a3 - Symbol pointer. *)
 proc _symbol_table_enter(v88: Word, v84: Word, v80: Word, v76: Word);
 begin
 	(* The first word in the symbol table is its length, get it. *)
-	v0 := _load_word(v76);
+	v0 := _load_word(v88);
 
 	(* Calculate the offset for the new symbol. *)
-	v4 := v0 * 4;
+	v4 := v0 * 12;
 	v4 := v4 + 4;
-	v4 := v76 + 4;
+	v4 := v88 + v4;
 
-	_memcpy(v4, @v80, 12);
+	_store_word(v84, v4);
+	v4 := v4 + 4;
+	_store_word(v80, v4);
+	v4 := v4 + 4;
+	_store_word(v76, v4);
 
 	(* Increment the symbol table length. *)
 	v0 := v0 + 1;
-	_store_word(v0, v76);
+	_store_word(v0, v88);
 end;
 
 proc _symbol_table_build();
 begin
-	_symbol_table_enter(@symbol_type_info_int, 3, symbol_builtin_name_int, @symbol_table_global);
+	(* Set the table length to 0. *)
-	_symbol_table_enter(@symbol_type_info_word, 4, symbol_builtin_name_word, @symbol_table_global);
+	_store_word(0, @symbol_table_global);
-	_symbol_table_enter(@symbol_type_info_pointer, 7, symbol_builtin_name_pointer, @symbol_table_global);
+
-	_symbol_table_enter(@symbol_type_info_char, 4, symbol_builtin_name_char, @symbol_table_global);
+	(* Enter built-in symbols. *)
-	_symbol_table_enter(@symbol_type_info_bool, 4, symbol_builtin_name_bool, @symbol_table_global);
+	_symbol_table_enter(@symbol_table_global, symbol_builtin_name_int, 3, @symbol_type_info_int);
+	_symbol_table_enter(@symbol_table_global, symbol_builtin_name_word, 4, @symbol_type_info_word);
+	_symbol_table_enter(@symbol_table_global, symbol_builtin_name_pointer, 7, @symbol_type_info_pointer);
+	_symbol_table_enter(@symbol_table_global, symbol_builtin_name_char, 4, @symbol_type_info_char);
+	_symbol_table_enter(@symbol_table_global, symbol_builtin_name_bool, 4, @symbol_type_info_bool);
 end;