Implement if-else

Rakefile

@@ -6,7 +6,9 @@
 require 'open3'
 require 'rake/clean'
 
-STAGES = Dir.glob('boot/stage*.elna').collect { |stage| File.basename stage, '.elna' }.sort
+STAGES = Dir.glob('boot/stage*.elna')
+  .collect { |stage| File.basename stage, '.elna' }
+  .sort { |a, b| a.delete_prefix('stage').to_i <=> b.delete_prefix('stage').to_i }
 
 CLEAN.include 'build/boot', 'build/valid'
 
@@ -39,17 +41,9 @@ end
 
 desc 'Convert previous stage language into the current stage language'
 task :convert do
-  File.open('boot/stage9.elna', 'w') do |current_stage|
+  File.open('boot/stage10.elna', 'w') do |current_stage|
-    File.readlines('boot/stage8.elna').each do |line|
+    File.readlines('boot/stage9.elna').each do |line|
-      comment_match = /^(\s*)#(.*)/.match line
+      current_stage << line
-
-      if comment_match.nil?
-        current_stage << line
-      elsif comment_match[2].empty?
-        current_stage << "\n"
-      else
-        current_stage << "#{comment_match[1]}(* #{comment_match[2].strip} *)\n"
-      end
     end
   end
 end

boot/stage8.elna

@@ -7,6 +7,10 @@
 # - Procedure calls in expressions.
 # - Comments between (* and *) are supported. These are still single line
 #   comments and they should be on a separate line.
+# - _syscall builtin. _syscall takes 7 arguments,
+#   the 7th argument gets stored in a7 before invoking ecall.
+#   Other arguments are saved in a0 through a5.
+# - New intrinsics: _load_byte, _load_word, _store_byte, _store_word.
 const
 	symbol_builtin_name_int := "Int";
 	symbol_builtin_name_word := "Word";
@@ -1403,7 +1407,13 @@ begin
 	_skip_empty_lines();
 	_compile_var_part();
 
-	_write_z(".section .text\n\0");
+	_write_z(".section .text\n\n\0");
+	_write_z(".type _syscall, @function\n_syscall:\n\tmv a7, a6\n\tecall\n\tret\n\n\0");
+	_write_z(".type _load_byte, @function\n_load_byte:\n\tlb a0, (a0)\nret\n\n\0");
+	_write_z(".type _load_word, @function\n_load_word:\n\tlw a0, (a0)\nret\n\n\0");
+	_write_z(".type _store_byte, @function\n_store_byte:\n\tsb a0, (a1)\nret\n\n\0");
+	_write_z(".type _store_word, @function\n_store_word:\n\tsw a0, (a1)\nret\n\n\0");
+
 .compile_module_loop:
 	_skip_empty_lines();
 

boot/stage9.elna

@@ -2,11 +2,12 @@
 (* v. 2.0. If a copy of the MPL was not distributed with this file, You can *)
 (* obtain one at https://mozilla.org/MPL/2.0/. *)
 
-(* Stage 8 compiler. *)
+(* Stage 9 compiler. *)
 
 (* - Procedure calls in expressions. *)
 (* - Comments between (* and *) are supported. These are still single line *)
 (* comments and they should be on a separate line. *)
+(* - if-else statements. *)
 const
 	symbol_builtin_name_int := "Int";
 	symbol_builtin_name_word := "Word";
@@ -45,6 +46,7 @@ var
 
 	compiler_strings_position: Pointer := @compiler_strings;
 	compiler_strings_length: Word := 0;
+	label_counter: Word := 0;
 	source_code_position: Pointer := @source_code;
 
 (* Calculates and returns the string token length between quotes, including the *)
@@ -93,16 +95,12 @@ begin
 
 	beq t1, t2, .add_string_end
 
-	la t2, compiler_strings_position
+	v8 := _load_byte(v0);
-	lw t3, (t2)
+	_store_byte(v8, compiler_strings_position);
-	sb t1, (t3)
+	_store_word(compiler_strings_position + 1, @compiler_strings_position);
-
+	v0 := v0 + 1;
-	addi t3, t3, 1
-	sw t3, (t2)
-
-	addi t0, t0, 1
-	sw t0, 0(sp)
 
+	lb t1, 8(sp)
 	li t2, '\\'
 	bne t1, t2, .add_string_increment
 
@@ -127,13 +125,7 @@ end;
 (* Returns the amount of bytes written in a0. *)
 proc _read_file();
 begin
-	mv a2, a1
+	_syscall(0, v88, v84, 0, 0, 0, 63);
-	mv a1, a0
-	(* STDIN. *)
-	li a0, 0
-	(* SYS_READ. *)
-	li a7, 63
-	ecall
 end;
 
 (* Writes to the standard output. *)
@@ -143,13 +135,7 @@ end;
 (* a1 - Buffer length. *)
 proc _write_s();
 begin
-	mv a2, a1
+	_syscall(1, v88, v84, 0, 0, 0, 64);
-	mv a1, a0
-	(* STDOUT. *)
-	li a0, 1
-	(* SYS_WRITE. *)
-	li a7, 64
-	ecall
 end;
 
 (* Writes a number to a string buffer. *)
@@ -317,9 +303,8 @@ begin
 	li t1, '.'
 	beq t0, t1, .read_token_next
 
-	lw a0, 0(sp)
+	v8 := _load_byte(v0);
-	lb a0, (a0)
+	_is_alnum(v8);
-	_is_alnum();
 	bnez a0, .read_token_next
 
 	goto .read_token_end;
@@ -464,10 +449,8 @@ begin
 	_advance_token(1);
 
 .compile_character_literal_end:
-	la t0, source_code_position
+	v0 := _load_byte(source_code_position);
-	lw t0, (t0)
+	_write_c(v0);
-	lb a0, (t0)
-	_write_c();
 
 	_write_c('\'');
 	_write_c('\n');
@@ -523,10 +506,8 @@ end;
 
 proc _compile_term();
 begin
-	la t0, source_code_position
+	v0 := _load_byte(source_code_position);
-	lw t0, (t0)
+	lb a0, 0(sp)
-	lb a0, (t0)
-	sw a0, 0(sp)
 
 	li t1, '\''
 	beq a0, t1, .compile_term_character_literal
@@ -925,13 +906,72 @@ begin
 	_write_z("mv a0, t0\n\0");
 end;
 
+(* Writes a label, .Ln, where n is a unique number. *)
+
+(* Parameters: *)
+(* a0 - Label counter. *)
+proc _write_label();
+begin
+	_write_z(".L\0");
+	_write_i(v88);
+end;
+
+proc _compile_if();
+begin
+	(* Skip "if ". *)
+	_advance_token(3);
+	(* Compile condition. *)
+	_compile_expression();
+	(* Skip " then" with newline. *)
+	_advance_token(6);
+
+	(* v0 is the label after the if statement. *)
+	v0 := label_counter;
+	_store_word(label_counter + 1, @label_counter);
+	(* v4 is the label in front of the next elsif condition or end. *)
+	v4 := label_counter;
+	_store_word(label_counter + 1, @label_counter);
+
+	_write_z("\tbeqz t0, \0");
+	_write_label(v4);
+	_write_c('\n');
+
+	_compile_procedure_body();
+
+	_write_z("\tj \0");
+	_write_label(v0);
+	_write_c('\n');
+
+	_write_label(v4);
+	_write_z(":\n\0");
+
+	_memcmp(source_code_position, "end", 3);
+	beqz a0, .compile_if_end
+
+	_memcmp(source_code_position, "else", 3);
+	beqz a0, .compile_if_else
+
+.compile_if_else:
+	(* Skip "else" and newline. *)
+	_advance_token(5);
+	_compile_procedure_body();
+
+.compile_if_end:
+	(* Skip "end". *)
+	_advance_token(3);
+
+	_write_label(v0);
+	_write_z(":\n\0");
+end;
+
 proc _compile_statement();
 begin
+	_skip_spaces();
 	(* This is a call if the statement starts with an underscore. *)
 	la t0, source_code_position
 	lw t0, (t0)
 	(* First character after alignment tab. *)
-	addi t0, t0, 1
+	(* addi t0, t0, 1 *)
 	lb t0, (t0)
 	
 	li t1, '_'
@@ -943,33 +983,42 @@ begin
 	li t1, 'v'
 	beq t0, t1, .compile_statement_assignment
 
+	li t1, 'i'
+	beq t0, t1, .compile_statement_if
+
 	(* keyword_ret contains "\tret", so it's 4 bytes long. *)
-	_memcmp(source_code_position, "\treturn", 7);
+	_memcmp(source_code_position, "return", 6);
 	beqz a0, .compile_statement_return
 
 	_compile_line();
 	goto .compile_statement_end;
 
 .compile_statement_call:
-	_advance_token(1);
+	(* _advance_token(1); *)
 	_compile_call();
 
 	goto .compile_statement_semicolon;
 
 .compile_statement_goto:
-	_advance_token(1);
+	(* _advance_token(1); *)
 	_compile_goto();
 
 	goto .compile_statement_semicolon;
 
 .compile_statement_assignment:
-	_advance_token(1);
+	(* _advance_token(1); *)
 	_compile_assignment();
 
 	goto .compile_statement_semicolon;
 
+.compile_statement_if:
+	(* _advance_token(1); *)
+	_compile_if();
+
+	goto .compile_statement_semicolon;
+
 .compile_statement_return:
-	_advance_token(1);
+	(* _advance_token(1); *)
 	_compile_return_statement();
 	_write_c('\n');
 
@@ -986,10 +1035,12 @@ proc _compile_procedure_body();
 begin
 .compile_procedure_body_loop:
 	_skip_empty_lines();
+	_skip_spaces();
 
-	(* 3 is "end" length. *)
 	_memcmp(source_code_position, "end", 3);
+	beqz a0, .compile_procedure_body_epilogue
 
+	_memcmp(source_code_position, "else", 4);
 	beqz a0, .compile_procedure_body_epilogue
 
 	_compile_statement();
@@ -1065,24 +1116,24 @@ begin
 	_advance_token(5);
 end;
 
-proc _skip_newlines();
+proc _skip_spaces();
 begin
 	(* Skip newlines. *)
 	la t0, source_code_position
 	lw t1, (t0)
 
-.skip_newlines_loop:
+.skip_spaces_loop:
 	lb t2, (t1)
-	li t3, '\n'
+	li t3, '\t'
-	bne t2, t3, .skip_newlines_end
+	bne t2, t3, .skip_spaces_end
-	beqz t2, .skip_newlines_end
+	beqz t2, .skip_spaces_end
 
 	addi t1, t1, 1
 	sw t1, (t0)
 
-	goto .skip_newlines_loop;
+	goto .skip_spaces_loop;
 
-.skip_newlines_end:
+.skip_spaces_end:
 end;
 
 (* Prints and skips a line. *)
@@ -1121,9 +1172,6 @@ begin
 	lw t2, 0(sp)
 	lb t0, (t2)
 
-	li t1, '#'
-	beq t0, t1, .skip_empty_lines_comment
-
 	li t1, '\n'
 	beq t0, t1, .skip_empty_lines_newline
 
@@ -1175,10 +1223,8 @@ begin
 	li t1, '@'
 	beq t0, t1, .compile_global_initializer_pointer
 
-	la a0, source_code_position
+	v0 := _load_byte(source_code_position);
-	lw a0, (a0)
+	_is_digit(v0);
-	lb a0, (a0)
-	_is_digit();
 	bnez a0, .compile_global_initializer_number
 
 	unimp
@@ -1373,7 +1419,13 @@ begin
 	_skip_empty_lines();
 	_compile_var_part();
 
-	_write_z(".section .text\n\0");
+	_write_z(".section .text\n\n\0");
+	_write_z(".type _syscall, @function\n_syscall:\n\tmv a7, a6\n\tecall\n\tret\n\n\0");
+	_write_z(".type _load_byte, @function\n_load_byte:\n\tlb a0, (a0)\nret\n\n\0");
+	_write_z(".type _load_word, @function\n_load_word:\n\tlw a0, (a0)\nret\n\n\0");
+	_write_z(".type _store_byte, @function\n_store_byte:\n\tsb a0, (a1)\nret\n\n\0");
+	_write_z(".type _store_word, @function\n_store_word:\n\tsw a0, (a1)\nret\n\n\0");
+
 .compile_module_loop:
 	_skip_empty_lines();
 
@@ -1413,10 +1465,9 @@ begin
 	lw t1, 4(sp)
 	bge t0, t1, .compile_end
 
-	lb a0, (t0)
+	v8 := _load_byte(v0);
-	addi t0, t0, 1
+	v0 := v0 + 1;
-	sw t0, 0(sp)
+	_write_c(v8);
-	_write_c();
 
 	j .compile_loop
 
@@ -1431,8 +1482,7 @@ end;
 (* a0 - Status code. *)
 proc _exit();
 begin
-	li a7, 93 # SYS_EXIT
+	_syscall(0, 0, 0, 0, 0, 0, 93);
-	ecall
 end;
 
 (* Inserts a symbol into the table. *)
@@ -1554,7 +1604,7 @@ begin
 	sw t1, (t0)
 end;
 
-proc _initialize_classification();
+proc _create_classification();
 begin
 	_assign_at(@classification, 1, 15);
 	_assign_at(@classification, 2, 1);
@@ -1688,13 +1738,13 @@ begin
 	v0 := 129;
 
 (* Set the remaining 129 - 256 bytes to transitionClassOther. *)
-.initialize_classification_loop:
+.create_classification_loop:
 	_assign_at(@classification, v0, 22);
 	v0 := v0 + 1;
 
 	lw t0, 0(sp)
 	li t1, 257
-	blt t0, t1, .initialize_classification_loop
+	blt t0, t1, .create_classification_loop
 end;
 
 (* Parameters: *)
@@ -1772,7 +1822,7 @@ end;
 (* - The next byte is the action that should be performed when transitioning. *)
 (* For the meaning of actions see labels in the lex_next function, which *)
 (* handles each action. *)
-proc _initialize_transitions();
+proc _create_transitions();
 begin
 	(* Start state. *)
 	_set_transition(1, 1, 1, 16);
@@ -1896,8 +1946,7 @@ end;
 (* Gets pointer to the current source text. *)
 proc _lexer_get_current();
 begin
-	_lexer_get_state();
+	v0 := _lexer_get_state();
-	sw a0, 0(sp)
 
 	return v0 + 4
 end;
@@ -1925,8 +1974,8 @@ end;
 (* One time lexer initialization. *)
 proc _lexer_initialize();
 begin
-	_initialize_classification();
+	_create_classification();
-	_initialize_transitions();
+	_create_transitions();
 end;
 
 (* Entry point. *)