Support preserved registers as identifiers

… in expressions

6 files changed, 868 insertions, 520 deletions

diff --git a/Rakefile b/Rakefile
index 3fa065e..ef74301 100644
--- a/Rakefile
+++ b/Rakefile
@@ -37,7 +37,7 @@ end
 directory 'build'
 
 desc 'Initial stage'
-file 'build/stage1' => ['boot/stage1.s', 'boot/common-boot.s', 'build'] do |t|
+file 'build/stage1' => ['boot/stage1.s', 'boot/common-boot.s', 'boot/tokenizer.s', 'build'] do |t|
   source = t.prerequisites.filter { |prerequisite| prerequisite.end_with? '.s' }
 
   sh CROSS_GCC, '-nostdlib', '-o', t.name, *source
diff --git a/boot/common-boot.s b/boot/common-boot.s
index e8eba52..e5796f1 100644
--- a/boot/common-boot.s
+++ b/boot/common-boot.s
@@ -1,5 +1,6 @@
 .global _is_alpha, _is_digit, _is_alnum, _is_upper, _is_lower
-.global _write_out, _read_file, _memcmp, _write_error, _put_char, _printi
+.global _write_out, _read_file, _write_error, _put_char, _printi
+.global _get, _memcmp
 .global _divide_by_zero_error, _exit
 
 .section .rodata
@@ -187,7 +188,9 @@ _write_out:
 # a0 - Buffer pointer.
 # a1 - Buffer size.
 #
-# Returns the result in a0.
+# Sets s1 to the buffer passed in a0.
+#
+# Returns the amount of bytes written in a0.
 .type _read_file, @function
 _read_file:
 	# Prologue.
@@ -196,9 +199,11 @@ _read_file:
 	sw s0, 0(sp)
 	addi s0, sp, 8
 
-	mv a2, a1
-	mv a1, a0
+	mv s1, a0
+
 	li a0, STDIN
+	mv a2, a1
+	mv a1, s1
 	li a7, SYS_READ
 	ecall
 
@@ -293,3 +298,11 @@ _put_char:
 	lw s0, 8(sp)
 	add sp, sp, 16
 	ret
+
+# a0 - Pointer to an array to get the first element.
+#
+# Dereferences a pointer and returns what is on the address in a0.
+.type _get, @function
+_get:
+	lw a0, (a0)
+	ret
diff --git a/boot/stage1.s b/boot/stage1.s
index 61dcdec..7137edc 100644
--- a/boot/stage1.s
+++ b/boot/stage1.s
@@ -207,6 +207,130 @@ _build_binary_expression:
 	addi sp, sp, 32
 	ret
 
+# Parameters:
+# a0 - Identifier length.
+# a1 - Register number as character.
+.type _build_identifier_expression, @function
+_build_identifier_expression:
+	# Prologue.
+	addi sp, sp, -32
+	sw ra, 28(sp)
+	sw s0, 24(sp)
+	addi s0, sp, 32
+
+	sw a0, 20(sp) # Identifier length.
+	sw a1, 16(sp) # Register number as character.
+
+	li t0, 0x61636f6c # loca
+	sw t0, 12(sp)
+	mv a0, s1
+	addi a1, sp, 12
+	li a2, 4
+	call _memcmp
+	beqz a0, .Lbuild_identifier_expression_local
+
+	lbu a0, (s1)
+	lw t0, 20(sp) 
+	addi t0, t0, -2
+	seqz t0, t0
+	addi t1, a0, -'s'
+	seqz t1, t1
+	and t0, t0, t1
+	bnez t0, .Lbuild_identifier_expression_saved
+
+	# Global identifier.
+	lw t1, 16(sp)
+	li t0, 0x00202c00 # \0,_
+	or t0, t0, t1
+	sw t0, 12(sp)
+	li t0, 0x6120616c # la a
+	sw t0, 8(sp)
+	addi a0, sp, 8
+	li a1, 7
+	call _write_out
+
+	mv a0, s1
+	lw a1, 20(sp)
+	call _write_out
+
+	li a0, '\n'
+	call _put_char
+
+	lbu a0, (s1)
+	call _is_upper
+	beqz a0, .Lbuild_identifier_expression_end
+
+	lw t1, 16(sp)
+	li t0, 0x0a290061 # a\0)\n
+	sll t2, t1, 8
+	or t0, t0, t2
+	sw t0, 12(sp)
+	li t0, 0x28202c00 # \0, (
+	or t0, t0, t1
+	sw t0, 8(sp)
+	li t0, 0x6120776c # lw a
+	sw t0, 4(sp)
+	addi a0, sp, 4
+	li a1, 12
+	call _write_out
+
+	j .Lbuild_identifier_expression_end
+
+.Lbuild_identifier_expression_saved:
+	li t0, 0x00202c00 # \0,_
+	lw t1, 16(sp)
+	or t0, t0, t1
+	sw t0, 12(sp)
+	li t0, 0x6120766d # mv a
+	sw t0, 8(sp)
+	addi a0, sp, 8
+	li a1, 7
+	call _write_out
+
+	mv a0, s1
+	lw a1, 20(sp)
+	call _write_out
+
+	li a0, '\n'
+	call _put_char
+
+	j .Lbuild_identifier_expression_end
+
+.Lbuild_identifier_expression_local:
+	lw t1, 16(sp)
+	li t0, 0x00202c00 # \0,_
+	or t0, t0, t1
+	sw t0, 12(sp)
+	li t0, 0x6120776c # lw a
+	sw t0, 8(sp)
+	addi a0, sp, 8
+	li a1, 7
+	call _write_out
+
+	mv a0, s1
+	lw a1, 20(sp)
+	addi a0, a0, 4 # Skip the "loca" variable prefix.
+	addi a1, a1, -4 # Skip the "loca" variable prefix.
+	call _write_out
+
+	li t0, 0x29707328 # (sp)
+	sw t0, 12(sp)
+	addi a0, sp, 12
+	li a1, 4
+	call _write_out
+	li a0, '\n'
+	call _put_char
+
+	j .Lbuild_identifier_expression_end
+
+.Lbuild_identifier_expression_end:
+
+	# Epilogue.
+	lw ra, 28(sp)
+	lw s0, 24(sp)
+	addi sp, sp, 32
+	ret
+
 # Evalutes an expression and saves the result in a0.
 #
 # a0 - X in aX, the register number to save the result.
@@ -242,31 +366,9 @@ _build_expression:
 	li t0, '_'
 	beq a0, t0, .Lbuild_expression_call
 
-	li t0, 0x61636f6c # loca
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 4
-	call _memcmp
-	beqz a0, .Lbuild_expression_identifier
-
-	# Named identifier.
-	lw t1, 28(sp)
-	li t0, 0x00202c00 # \0,_
-	or t0, t0, t1
-	sw t0, 8(sp)
-	li t0, 0x6120616c # la a
-	sw t0, 4(sp)
-	addi a0, sp, 4
-	li a1, 7
-	call _write_out
-
-	lw a0, 24(sp)
-	lw a1, 20(sp)
-	call _write_out
-
-	li a0, '\n'
-	call _put_char
+	lw a0, 20(sp)
+	lw a1, 28(sp)
+	call _build_identifier_expression
 
 	j .Lbuild_expression_advance
 
@@ -313,33 +415,6 @@ _build_expression:
 
 	j .Lbuild_expression_advance
 
-.Lbuild_expression_identifier:
-	lw t1, 28(sp)
-	li t0, 0x00202c00 # \0,_
-	or t0, t0, t1
-	sw t0, 16(sp)
-	li t0, 0x6120776c # lw a
-	sw t0, 12(sp)
-	addi a0, sp, 12
-	li a1, 7
-	call _write_out
-
-	lw a0, 24(sp)
-	lw a1, 20(sp)
-	addi a0, a0, 4 # Skip the "loca" variable prefix.
-	addi a1, a1, -4 # Skip the "loca" variable prefix.
-	call _write_out
-
-	li t0, '\n'
-	sw t0, 16(sp)
-	li t0, 0x29707328 # (sp)
-	sw t0, 12(sp)
-	addi a0, sp, 12
-	li a1, 5
-	call _write_out
-
-	j .Lbuild_expression_advance
-
 .Lbuild_expression_call:
 	lw a0, 24(sp)
 	lw a1, 20(sp)
@@ -683,24 +758,6 @@ _skip_spaces:
 .Lspace_loop_end:
 	ret
 
-# Skips tabs at the line beginning.
-.type _skip_indentation, @function
-_skip_indentation:
-.Lskip_indentation_do:
-	lbu t0, (s1)
-
-	li t1, '\t'
-	beq t0, t1, .Lskip_indentation_skip
-
-	j .Lskip_indentation_end
-
-.Lskip_indentation_skip:
-	addi s1, s1, 1
-	j .Lskip_indentation_do
-
-.Lskip_indentation_end:
-	ret
-
 # Parameters:
 # a0 - Line length.
 .type _skip_comment, @function
@@ -1134,7 +1191,7 @@ _compile_procedure:
 
 	# Generate the body of the procedure.
 .Lcompile_procedure_body:
-	call _skip_indentation
+	call _skip_spaces
 	call _read_line
 	sw a0, 12(sp)
 	li t0, 0x0a646e65 # end\n
@@ -1427,23 +1484,19 @@ _compile_line:
 	li t1, '('
 	beq t0, t1, .Lcompile_line_comment
 
-	li t0, 0x0a6d6172 # ram\n
-	sw t0, 12(sp)
 	li t0, 0x676f7270 # prog
-	sw t0, 8(sp)
+	sw t0, 12(sp)
 	mv a0, s1
-	addi a1, sp, 8
-	li a2, 8
+	addi a1, sp, 12
+	li a2, 4
 	call _memcmp
 	beqz a0, .Lcompile_line_program
 
-	li t0, 0x0a74 # t\n
-	sw t0, 12(sp)
 	li t0, 0x736e6f63 # cons
-	sw t0, 8(sp)
+	sw t0, 12(sp)
 	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
+	addi a1, sp, 12
+	li a2, 4
 	call _memcmp
 	beqz a0, .Lcompile_line_const
 
@@ -1455,23 +1508,19 @@ _compile_line:
 	call _memcmp
 	beqz a0, .Lcompile_line_var
 
-	li t0, 0x20 # _
-	sw t0, 12(sp)
 	li t0, 0x636f7270 # proc
-	sw t0, 8(sp)
+	sw t0, 12(sp)
 	mv a0, s1
-	addi a1, sp, 8
-	li a2, 5
+	addi a1, sp, 12
+	li a2, 4
 	call _memcmp
 	beqz a0, .Lcompile_line_procedure
 
-	li t0, 0x0a6e # n\n
-	sw t0, 12(sp)
 	li t0, 0x69676562 # begi
-	sw t0, 8(sp)
+	sw t0, 12(sp)
 	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
+	addi a1, sp, 12
+	li a2, 4
 	call _memcmp
 	beqz a0, .Lcompile_line_begin
 
@@ -1491,13 +1540,11 @@ _compile_line:
 	call _memcmp
 	beqz a0, .Lcompile_line_identifier
 
-	li t0, 0x7472 # rt
-	sw t0, 12(sp)
 	li t0, 0x6f706d69 # impo
-	sw t0, 8(sp)
+	sw t0, 12(sp)
 	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
+	addi a1, sp, 12
+	li a2, 4
 	call _memcmp
 	beqz a0, .Lcompile_line_import
 
@@ -1509,13 +1556,11 @@ _compile_line:
 	call _memcmp
 	beqz a0, .Lcompile_line_goto
 
-	li t0, 0x6e72 # rn
-	sw t0, 12(sp)
 	li t0, 0x75746572 # retu
-	sw t0, 8(sp)
+	sw t0, 12(sp)
 	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
+	addi a1, sp, 12
+	li a2, 4
 	call _memcmp
 	beqz a0, .Lcompile_line_return
 
@@ -1716,7 +1761,7 @@ _compile:
 	lbu t0, (s1) # t0 = Current character.
 	beqz t0, .Lcompile_end # Exit the loop on the NUL character.
 
-	call _skip_indentation
+	call _skip_spaces
 	call _read_line
 	lw a1, 4(sp)
 	call _compile_line
@@ -1736,16 +1781,35 @@ _compile:
 	addi sp, sp, 16
 	ret
 
-# Entry point.
-.type _start, @function
-_start:
+.type _main, @function
+_main:
+	# Prologue.
+	addi sp, sp, -8
+	sw ra, 4(sp)
+	sw s0, 0(sp)
+	addi s0, sp, 8
+
 	# Read the source from the standard input.
 	la a0, source_code
 	li a1, SOURCE_BUFFER_SIZE # Buffer size.
 	call _read_file
 
 	li s2, 1
-	la s1, source_code # s1 = Source code position.
+
+	# Epilogue.
+	lw ra, 4(sp)
+	lw s0, 0(sp)
+	addi sp, sp, 8
+	ret
+
+# Entry point.
+.type _start, @function
+_start:
+	call _tokenizer_initialize
+	li a1, 50
+	call _write_error
+
+	call _main
 	call _compile
 
 	# Call exit.
diff --git a/boot/stage2.elna b/boot/stage2.elna
index 0eb713c..3cb2deb 100644
--- a/boot/stage2.elna
+++ b/boot/stage2.elna
@@ -39,7 +39,10 @@ begin
 end
 
 proc _build_binary_expression()
-var loca0, loca4, loca8, loca20: Word
+var
+	loca0, loca4, loca8, loca16, loca20: Word
+	loca12: ^Byte
+	loca24: Bool
 begin
 	_build_expression(0)
 
@@ -48,60 +51,51 @@ begin
 
 	_skip_spaces()
 	loca20 := _read_token()
+	loca12 := _current()
+
+	loca16 := 0x26 (* & *)
+	loca24 := _token_compare(loca12, loca20, @loca16)
+	if loca24 = 0 then
+		goto .L_build_binary_expression_and
+	end
+
+	loca16 := 0x726f (* or *)
+	loca24 := _token_compare(loca12, loca20, @loca16)
+	if loca24 = 0 then
+		goto .L_build_binary_expression_or
+	end
+
+	loca16 := 0x3d (* = *)
+	loca24 := _token_compare(loca12, loca20, @loca16)
+	if loca24 = 0 then
+		goto .L_build_binary_expression_equal
+	end
+
+	loca16 := 0x2b (* + *)
+	loca24 := _token_compare(loca12, loca20, @loca16)
+	if loca24 = 0 then
+		goto .L_build_binary_expression_plus
+	end
+
+	loca16 := 0x2d (* - *)
+	loca24 := _token_compare(loca12, loca20, @loca16)
+	if loca24 = 0 then
+		goto .L_build_binary_expression_minus
+	end
 
-	li t0, 0x26 # &
-	sw t0, 16(sp)
-	mv a0, s1
-	lw a1, 20(sp)
-	addi a2, sp, 16
-	call _token_compare
-	beqz a0, .L_build_binary_expression_and
-
-	li t0, 0x726f # or
-	sw t0, 16(sp)
-	mv a0, s1
-	lw a1, 20(sp)
-	addi a2, sp, 16
-	call _token_compare
-	beqz a0, .L_build_binary_expression_or
-
-	li t0, 0x3d # =
-	sw t0, 16(sp)
-	mv a0, s1
-	lw a1, 20(sp)
-	addi a2, sp, 16
-	call _token_compare
-	beqz a0, .L_build_binary_expression_equal
-
-	li t0, 0x2b # +
-	sw t0, 16(sp)
-	mv a0, s1
-	lw a1, 20(sp)
-	addi a2, sp, 16
-	call _token_compare
-	beqz a0, .L_build_binary_expression_plus
-
-	li t0, 0x2d # -
-	sw t0, 16(sp)
-	mv a0, s1
-	lw a1, 20(sp)
-	addi a2, sp, 16
-	call _token_compare
-	beqz a0, .L_build_binary_expression_minus
-
-	li t0, 0x2a # *
-	sw t0, 16(sp)
-	mv a0, s1
-	lw a1, 20(sp)
-	addi a2, sp, 16
-	call _token_compare
-	beqz a0, .L_build_binary_expression_product
+	loca16 := 0x2a (* * *)
+	loca24 := _token_compare(loca12, loca20, @loca16)
+	if loca24 = 0 then
+		goto .L_build_binary_expression_product
+	end
 
 	goto .Lbuild_binary_expression_end
 
 	.L_build_binary_expression_equal
 	_advance(1) (* Skip =. *)
 	_build_expression(1)
+
+	loca0 := 0x627573(* sub *)
 	_write_out(@loca0, 3)
 	_write_out(@loca4, 4)
 	_write_out(@loca4, 4)
@@ -110,7 +104,8 @@ begin
 	loca0 := 0x7a716573 (* seqz *)
 	_write_out(@loca0, 4)
 	_write_out(@loca4, 4)
-	_write_out(@loca4, 4)
+	_write_out(@loca4, 3)
+	_put_char(0x0a) (* \n *)
 
 	goto .Lbuild_binary_expression_end
 
@@ -172,6 +167,67 @@ begin
 	.Lbuild_binary_expression_end
 end
 
+proc _build_identifier_expression(loca84: Word, loca80: Byte)
+begin
+	loca24 := _current()
+	loca0 := 0x61636f6c (* loca *)
+	loca0 := _memcmp(@loca0, loca24, 4)
+
+	if loca0 = 0 then
+		loca8 := 0x6120776c (* lw a *)
+		_write_out(@loca8, 4)
+		loca8 := 0x00202c00 or loca80 (* \0,_ *)
+		_write_out(@loca8, 3)
+
+		loca4 := loca24 + 4
+		loca0 := loca84 - 4
+		_write_out(loca4, loca0) (* Skip the "loca" variable prefix. *)
+
+		loca8 := 0x29707328 (* (sp) *)
+		_write_out(@loca8, 4)
+		_put_char(0x0a) (* \n *)
+
+		goto .Lbuild_identifier_expression_end
+	end
+	loca0 := _front(loca24)
+	loca8 := loca84 = 2
+	loca12 := loca0 = 0x73
+	if loca8 & loca12 then
+		loca8 := 0x6120766d (* mv a *)
+		_write_out(@loca8, 4)
+		loca8 := 0x00202c00 or loca80 (* \0,_ *)
+		_write_out(@loca8, 3)
+		_write_out(loca24, loca84)
+		_put_char(0x0a) (* \n *)
+
+		goto .Lbuild_identifier_expression_end
+	end
+
+	(* Global identifier. *)
+	loca8 := 0x6120616c (* la a *)
+	_write_out(@loca8, 4)
+	loca8 := 0x00202c00 or loca80
+	_write_out(@loca8, 3)
+
+	_write_out(loca24, loca84)
+	_put_char(0x0a)
+
+	if _is_upper(loca0) then
+		loca8 := 0x6120776c (* lw a *)
+		_write_out(@loca8, 4)
+		loca8 := 0x28202c00 or loca28 (* \0, ( *)
+		_write_out(@loca8, 4)
+		_put_char(0x61) (* a *)
+		_put_char(loca28)
+		_put_char(0x29) (* ) *)
+		_put_char(0x0a) (* \n *)
+
+		goto .Lbuild_identifier_expression_end
+	end
+
+	.Lbuild_identifier_expression_end
+end
+
 (*
 Evalutes an expression and saves the result in a0.
 
@@ -188,41 +244,28 @@ begin
 	_skip_spaces()
 	loca20 := _read_token()
 	loca24 := _current()
+	loca0 := _front(loca24)
 
-	lbu a0, (s1)
-	li t0, '-'
-	beq a0, t0, .Lbuild_expression_negate
+	(* - *)
+	if loca0 = 0x2d then
+		goto .Lbuild_expression_negate
+	end
 
-	lbu a0, (s1)
-	li t0, '@'
-	beq a0, t0, .Lbuild_expression_address
+	(* @ *)
+	if loca0 = 0x40 then
+		goto .Lbuild_expression_address
+	end
 
-	loca0 := _front()
 	if _is_digit(loca0) then
 		goto .Lbuild_expression_literal
 	end
 
-	lbu a0, (s1)
-	li t0, '_'
-	beq a0, t0, .Lbuild_expression_call
-
-	li t0, 0x61636f6c # loca
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 4
-	call _memcmp
-	beqz a0, .Lbuild_expression_identifier
-
-	(* Named identifier. *)
-	loca8 := 0x6120616c (* la a *)
-	_write_out(@loca8, 4)
-	loca8 := 0x00202c00 or loca28
-	_write_out(@loca8, 3)
-
-	_write_out(loca24, loca20)
-	_put_char(0x0a)
+	(* _ *)
+	if loca0 = 0x5f then
+		goto .Lbuild_expression_call
+	end
 
+	_build_identifier_expression(loca20, loca28);
 	goto .Lbuild_expression_advance
 
 	.Lbuild_expression_negate
@@ -263,22 +306,6 @@ begin
 
 	goto .Lbuild_expression_advance
 
-	.Lbuild_expression_identifier
-	loca8 := 0x6120776c (* lw a *)
-	_write_out(@loca8, 4)
-	loca8 := 0x00202c00 or loca28 # \0,_
-	_write_out(@loca8, 3)
-
-	loca4 := loca24 + 4
-	loca0 := loca20 - 4
-	_write_out(loca4, loca0) (* Skip the "loca" variable prefix. *)
-
-	loca8 := 0x29707328 (* (sp) *)
-	_write_out(@loca8, 4)
-	_put_char(0x0a) (* \n *)
-
-	goto .Lbuild_expression_advance
-
 	.Lbuild_expression_call
 	_advance(loca20)
 	_advance(1)
@@ -313,6 +340,7 @@ proc _compile_identifier()
 var
 	loca0, loca16, loca8: Word
 	loca20, loca12: ^Byte
+	loca4: Bool
 begin
 	(* Save the pointer to the identifier and its length on the stack. *)
 	loca20 := _current()
@@ -325,21 +353,18 @@ begin
 	loca12 := _current()
 	loca8 := _read_token()
 
-	_advance(loca8) # Skip that token.
+	_advance(loca8) (* Skip that token. *)
 	_skip_spaces()
 
-	li t0, 0x3d3a # :=
-	sw t0, 4(sp)
-	lw a0, 12(sp)
-	lw a1, 8(sp)
-	addi a2, sp, 4
-	call _token_compare
-	beqz a0, .Lcompile_identifier_assign
+	loca0 := 0x3d3a (* := *)
+	loca4 := _token_compare(loca12, loca8, @loca0)
+	if loca4 = 0 then
+		goto .Lcompile_identifier_assign
+	end
 
-	lw t0, 12(sp)
-	lbu t0, (t0)
-	li t1, 0x28 # (
-	beq t0, t1, .Lcompile_identifier_call
+	if _front(loca12) = 0x28 then
+		goto .Lcompile_identifier_call
+	end
 
 	goto .Lcompile_identifier_end
 
@@ -379,14 +404,16 @@ Returns the procedure result in a0.
 proc _compile_call(loca84: ^Byte, loca80: Word)
 var
 	loca0, loca4, loca12: Word
+	loca8: ^Byte
 begin
 	loca12 := 0 (* Argument count for a procedure call. *)
 
 	.Lcompile_call_paren
 	_skip_spaces()
-	lbu t0, (s1)
-	li t1, 0x29 # )
-	beq t0, t1, .Lcompile_call_complete
+	loca8 := _current()
+	if _front(loca8) = 0x29 then
+		goto .Lcompile_call_complete
+	end
 
 	.Lcompile_call_argument
 	_build_expression(0)
@@ -409,9 +436,11 @@ begin
 	_put_char(0x0a) (* \n *)
 
 	_skip_spaces()
-	lbu t0, (s1)
-	li t1, ','
-	bne t0, t1, .Lcompile_call_paren
+	loca8 := _current()
+	loca0 := _front(loca8) = 0x2c
+	if loca0 = 0 then
+		goto .Lcompile_call_paren
+	end
 
 	loca12 := loca12 + 1 (* Argument count for a procedure call. *)
 
@@ -497,64 +526,97 @@ Reads a token and returns its length in a0.
 _read_token doesn't change s1, it finds the length of the token s1 is pointing to.
 *)
 proc _read_token()
-var loca4: Word
+var
+	loca0, loca4: Word
+	loca8: ^Byte
 begin
-	lbu t0, (s1) # t0 = Current character.
+	loca8 := _current()
+	loca0 := _front(loca8) (* t0 = Current character. *)
 	loca4 := 0
 
-	li t1, '.'
-	beq t0, t1, .Ltoken_character_single
+	(* . *)
+	if loca0 = 0x2e then
+		goto .Ltoken_character_single
+	end
 
-	li t1, ','
-	beq t0, t1, .Ltoken_character_single
+	(* , *)
+	if loca0 = 0x2c then
+		goto .Ltoken_character_single
+	end
 
-	li t1, ':'
-	beq t0, t1, .Ltoken_character_colon
+	(* : *)
+	if loca0 = 0x3a then
+		goto .Ltoken_character_colon
+	end
 
-	li t1, ';'
-	beq t0, t1, .Ltoken_character_single
+	(* ; *)
+	if loca0 = 0x3b then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '('
-	beq t0, t1, .Ltoken_character_single
+	(* ( *)
+	if loca0 = 0x28 then
+		goto .Ltoken_character_single
+	end
 
-	li t1, ')'
-	beq t0, t1, .Ltoken_character_single
+	(* ) *)
+	if loca0 = 0x29 then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '['
-	beq t0, t1, .Ltoken_character_single
+	(* [ *)
+	if loca0 = 0x5b then
+		goto .Ltoken_character_single
+	end
 
-	li t1, ']'
-	beq t0, t1, .Ltoken_character_single
+	(* ] *)
+	if loca0 = 0x5d then
+		goto .Ltoken_character_single
+	end
+
+	(* ^ *)
+	if loca0 = 0x5e then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '^'
-	beq t0, t1, .Ltoken_character_single
+	(* & *)
+	if loca0 = 0x26 then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '&'
-	beq t0, t1, .Ltoken_character_single
+	(* = *)
+	if loca0 = 0x3d then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '='
-	beq t0, t1, .Ltoken_character_single
+	(* + *)
+	if loca0 = 0x2b then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '+'
-	beq t0, t1, .Ltoken_character_single
+	(* - *)
+	if loca0 = 0x2d then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '-'
-	beq t0, t1, .Ltoken_character_single
+	(* * *)
+	if loca0 = 0x2a then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '*'
-	beq t0, t1, .Ltoken_character_single
+	(* @ *)
+	if loca0 = 0x40 then
+		goto .Ltoken_character_single
+	end
 
-	li t1, '@'
-	beq t0, t1, .Ltoken_character_single
 	(* Expect an identifier or a number. *)
 	.Ltoken_character_loop_do
-	lw t6, 4(sp)
-	add t1, s1, t6
-	lbu a0, (t1) # a0 = Current character.
+	loca0 := loca8 + loca4
+	loca0 := _front(loca0)
 
-	call _is_alnum
-
-	beqz a0, .Ltoken_character_end
+	if _is_alnum(loca0) = 0 then
+		goto .Ltoken_character_end
+	end
 	loca4 := loca4 + 1
 	goto .Ltoken_character_loop_do
 
@@ -563,31 +625,46 @@ begin
 	goto .Ltoken_character_end
 
 	.Ltoken_character_colon
-	lbu t0, 1(s1) # t0 = The character after the colon.
+	loca0 := loca8 + 1
+	loca0 := _front(loca0) (* t0 = The character after the colon. *)
 	loca4 := loca4 + 1
 
-	li t1, '='
-	beq t0, t1, .Ltoken_character_single
+	(* = *)
+	if loca0 = 0x3d then
+		goto  .Ltoken_character_single
+	end
 	goto .Ltoken_character_end
 
 	.Ltoken_character_end
-	lw a0, 4(sp)
+	return loca4
 end
 
 (* Skips the spaces till the next non space character. *)
 proc _skip_spaces()
+var
+	loca0: Byte
+	loca4: ^Byte
 begin
 	.Lspace_loop_do
-	lbu t0, (s1) # t0 = Current character.
+	loca4 := _current()
+	loca0 := _front(loca4) (* t0 = Current character. *)
 
-	li t1, ' '
-	beq t0, t1, .Lspace_loop_repeat
-	li t1, '\t'
-	beq t0, t1, .Lspace_loop_repeat
-	li t1, '\n'
-	beq t0, t1, .Lspace_loop_repeat
-	li t1, '\r'
-	beq t0, t1, .Lspace_loop_repeat
+	(* _ *)
+	if loca0 = 0x20 then
+		goto .Lspace_loop_repeat
+	end
+	(* \t *)
+	if loca0 = 0x09 then
+		goto .Lspace_loop_repeat
+	end
+	(* \n *)
+	if loca0 = 0x0a then
+		goto .Lspace_loop_repeat
+	end
+	(* \r *)
+	if loca0 = 0x0d then
+		goto .Lspace_loop_repeat
+	end
 
 	goto .Lspace_loop_end
 	.Lspace_loop_repeat
@@ -597,50 +674,37 @@ begin
 	.Lspace_loop_end
 end
 
-(* Skips tabs at the line beginning. *)
-proc _skip_indentation()
-begin
-	.Lskip_indentation_do
-	lbu t0, (s1)
-
-	li t1, '\t'
-	beq t0, t1, .Lskip_indentation_skip
-
-	goto .Lskip_indentation_end
-
-	.Lskip_indentation_skip
-	_advance(1)
-	goto .Lskip_indentation_do
-
-	.Lskip_indentation_end
-end
-
 (*
 Parameters:
 	a0 - Line length.
 *)
 proc _skip_comment(loca84: Word)
+var
+	loca0: ^Byte
+	loca4: Word
+	loca8: Int
 begin
+	loca0 := _current()
+
 	(* Check whether this is a comment. *)
-	li t0, 0x2a28 # (*
-	sw t0, 4(sp)
-	addi a0, sp, 4
-	mv a1, s1
-	li a2, 2
-	call _memcmp
-	bnez a0, .Lskip_comment_end
+	loca4 := 0x2a28 (* ( and * *)
+	loca8 := _memcmp(loca0, @loca4, 2)
+	if loca8 = 0 then
+		goto .Lskip_comment_continue
+	end
+	goto .Lskip_comment_end
 
+	.Lskip_comment_continue
 	_advance(2) (* Skip (*. *)
 
-	li t0, 0x292a # *)
-	sw t0, 4(sp)
+	loca4 := 0x292a (* ( and * *)
 
 	.Lskip_comment_loop
-	addi a0, sp, 4
-	mv a1, s1
-	li a2, 2
-	call _memcmp
-	beqz a0, .Lskip_comment_close
+	loca0 := _current()
+	loca8 := _memcmp(loca0, @loca4, 2)
+	if loca8 = 0 then
+		goto .Lskip_comment_close
+	end
 
 	_advance(1)
 
@@ -687,7 +751,9 @@ begin
 end
 
 proc _compile_constant_section()
-var loca0: Word
+var
+	loca0: Word
+	loca4: ^Byte
 begin
 	(* .section .rodata *)
 	loca0 := 0x6365732e (* .sec *)
@@ -705,9 +771,11 @@ begin
 
 	.Lcompile_constant_section_item
 	_skip_spaces()
-	lbu a0, (s1)
-	call _is_upper
-	beqz a0, .Lcompile_constant_section_end
+	loca4 := _current()
+	loca0 := _front(loca4)
+	if _is_upper(loca0) = 0 then
+		goto .Lcompile_constant_section_end
+	end
 
 	_compile_constant()
 	goto .Lcompile_constant_section_item
@@ -746,7 +814,9 @@ begin
 end
 
 proc _compile_variable_section()
-var loca0: Word
+var
+	loca0: Word
+	loca4: ^Byte
 begin
 	(* .section .bss *)
 	loca0 := 0x6365732e (* .sec *)
@@ -762,10 +832,12 @@ begin
 
 	.Lcompile_variable_section_item
 	_skip_spaces()
-	lbu a0, (s1)
-	call _is_lower
-	beqz a0, .Lcompile_variable_section_end
+	loca4 := _current()
+	loca0 := _front(loca4)
 
+	if _is_lower(loca0) = 0 then
+		goto .Lcompile_variable_section_end
+	end
 	_compile_variable()
 	goto .Lcompile_variable_section_item
 
@@ -846,7 +918,7 @@ end
 proc _compile_procedure()
 var
 	loca0, loca4, loca8, loca12, loca16: Word
-	loca20: ^Char
+	loca20, loca24: ^Byte
 begin
 	_advance(5) (* Skip proc_ *)
 	loca16 := _read_token()
@@ -887,15 +959,15 @@ begin
 	*)
 	.Lcompile_procedure_begin
 	_skip_spaces()
-	call _read_token
+	loca0 := _read_token()
 
-	mv a1, a0
-	mv a0, s1
-	addi a2, sp, 8
-	add s1, s1, a1
-	call _token_compare
+	loca24 := _current()
+	_advance(loca0)
+	loca0 := _token_compare(loca24, loca0, @loca8)
 
-	bnez a0, .Lcompile_procedure_begin
+	if loca0 = 1 then
+		goto .Lcompile_procedure_begin
+	end
 
 	(* Generate the procedure prologue with a predefined stack size. *)
 	loca0 := 0x69646461 (* addi *)
@@ -982,33 +1054,30 @@ begin
 
 	(* Generate the body of the procedure. *)
 	.Lcompile_procedure_body
-	_skip_indentation()
-	call _read_line
-	sw a0, 12(sp)
-	li t0, 0x0a646e65 # end\n
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 4
-	call _memcmp
-
-	beqz a0, .Lcompile_procedure_end
-
-	lw a0, 12(sp)
-	call _compile_line
+	_skip_spaces()
+	loca12 := _read_line()
+	loca8 := 0x0a646e65 (* end\n *)
+	loca24 := _current()
+	loca8 := _memcmp(loca24, @loca8, 4)
+
+	if loca8 = 0 then
+		goto .Lcompile_procedure_end
+	end
+
+	_compile_line(loca12)
 	goto .Lcompile_procedure_body
 
 	.Lcompile_procedure_end
 	_advance(4) (* Skip end\n. *)
 
 	(* Generate the procedure epilogue with a predefined stack size. *)
-	loca0 := 0x7220776c # lw r
+	loca0 := 0x7220776c (* lw r *)
 	_write_out(@loca0, 4)
-	loca0 := 0x39202c61 # a, 9
+	loca0 := 0x39202c61 (* a, 9 *)
 	_write_out(@loca0, 4)
-	loca0 := 0x70732832 # 2(sp
+	loca0 := 0x70732832 (* 2(sp *)
 	_write_out(@loca0, 4)
-	loca0 := 0x0a29 # )\n
+	loca0 := 0x0a29 (* )\n *)
 	_write_out(@loca0, 2)
 
 	loca0 := 0x7320776c (* lw s *)
@@ -1043,41 +1112,51 @@ Compares two string, which of one has a length, the other one is null-terminated
 
 If the strings match sets a0 to 0, otherwise sets it to 1.
 *)
-proc _token_compare()
+proc _token_compare(loca84: ^Byte, loca80: Word, loca76: ^Byte)
+var
+	loca0: Bool
+	loca4, loca12: Byte
+	loca8: Word
 begin
-	addi t0, a0, 0
-	addi t1, a1, 0
-	addi t2, a2, 0
-
 	.Ltoken_compare_loop
-	lbu t3, (t2)
+	loca4 := _front(loca76)
 
 	(*
 	Will only be 0 if the current character in the null terminated string is \0 and the remaining length of the
 	another string is 0.
 	*)
-	or t4, t3, t1
-	beqz t4, .Ltoken_compare_equal
-
-	beqz t1, .Ltoken_compare_not_equal
-	beqz t3, .Ltoken_compare_not_equal
+	loca8 := loca4 or loca80
+	if loca8 = 0 then
+		goto .Ltoken_compare_equal
+	end
+	if loca80 = 0 then
+		goto .Ltoken_compare_not_equal
+	end
+	if loca4 = 0 then
+		goto .Ltoken_compare_not_equal
+	end
+	loca12 := _front(loca84)
+	if loca4 = loca12 then
+		goto .Ltoken_compare_continue
+	end
+	goto .Ltoken_compare_not_equal
 
-	lbu t4, (t0)
-	bne t3, t4, .Ltoken_compare_not_equal
+	.Ltoken_compare_continue
 
-	addi t0, t0, 1
-	addi t1, t1, -1
-	addi t2, t2, 1
+	loca84 := loca84 + 1
+	loca80 := loca80 - 1
+	loca76 := loca76 + 1
 	goto .Ltoken_compare_loop
 
 	.Ltoken_compare_not_equal
-	li a0, 1
+	loca0 := 1
 	goto .Ltoken_compare_end
 
 	.Ltoken_compare_equal
-	li a0, 0
+	loca0 := 0
 
 	.Ltoken_compare_end
+	return loca0
 end
 
 proc _compile_goto()
@@ -1112,15 +1191,13 @@ begin
 	loca0 := _current()
 	_write_out(loca0, loca84)
 
-	lw t0, 84(sp) # Line length.
-	mv t1, s1 # Line start.
-
-	add t1, t1, t0
-	addi t1, t1, -1 # Last character on the line.
+	loca0 := loca0 + loca84
+	loca0 := loca0 - 1 (* Last character on the line. *)
 
-	lbu t1, (t1)
-	li t2, ':'
-	beq t1, t2, .Lcompile_label_colon
+	loca0 := _front(loca0)
+	if loca0 = 0x3a then
+		goto .Lcompile_label_colon
+	end
 
 	_put_char(0x3a) (* : *)
 
@@ -1161,8 +1238,7 @@ begin
 
 	(* Write the label *)
 	_write_out(@loca16, 4)
-	mv a0, s2
-	call _printi
+	_printi(s2)
 
 	_put_char(0x0a) (* \n *)
 
@@ -1182,13 +1258,13 @@ begin
 
 	(* Write the label *)
 	_write_out(@loca16, 4)
-	mv a0, s2
-	call _printi
+	_printi(s2)
 
 	loca12 := 0x0a3a0a3a (* :\n:\n *)
 	_write_out(@loca12, 2)
 
-	addi s2, s2, 1 # Increment the label counter.
+	(* Increment the label counter. *)
+	addi s2, s2, 1
 	_advance(4) (* Skip the end with newline. *)
 end
 
@@ -1202,119 +1278,99 @@ Returns 1 in a0 if the parsed line contained a text section element such a
 procedure or the program entry point. Otherwise sets a0 to 0.
 *)
 proc _compile_line(loca84: Word, loca80: Bool)
+var
+	loca0: Char
+	loca4: Int
+	loca8: Bool
+	loca12: Word
+	loca16: ^Byte
 begin
-	beqz a0, .Lcompile_line_empty # Skip an empty line.
-
-	lbu t0, (s1)
-	li t1, '('
-	beq t0, t1, .Lcompile_line_comment
-
-	li t0, 0x0a6d6172 # ram\n
-	sw t0, 12(sp)
-	li t0, 0x676f7270 # prog
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 8
-	call _memcmp
-	beqz a0, .Lcompile_line_program
-
-	li t0, 0x0a74 # t\n
-	sw t0, 12(sp)
-	li t0, 0x736e6f63 # cons
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
-	call _memcmp
-	beqz a0, .Lcompile_line_const
-
-	li t0, 0x0a726176 # var\n
-	sw t0, 12(sp)
-	mv a0, s1
-	addi a1, sp, 12
-	li a2, 4
-	call _memcmp
-	beqz a0, .Lcompile_line_var
-
-	li t0, 0x20 # _
-	sw t0, 12(sp)
-	li t0, 0x636f7270 # proc
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 5
-	call _memcmp
-	beqz a0, .Lcompile_line_procedure
-
-	li t0, 0x0a6e # n\n
-	sw t0, 12(sp)
-	li t0, 0x69676562 # begi
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
-	call _memcmp
-	beqz a0, .Lcompile_line_begin
-
-	li t0, 0x2e646e65 # end.
-	sw t0, 12(sp)
-	mv a0, s1
-	addi a1, sp, 12
-	li a2, 4
-	call _memcmp
-	beqz a0, .Lcompile_line_exit
-
-	li t0, 0x61636f6c # loca
-	sw t0, 12(sp)
-	mv a0, s1
-	addi a1, sp, 12
-	li a2, 4
-	call _memcmp
-	beqz a0, .Lcompile_line_identifier
-
-	li t0, 0x7472 # rt
-	sw t0, 12(sp)
-	li t0, 0x6f706d69 # impo
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
-	call _memcmp
-	beqz a0, .Lcompile_line_import
-
-	li t0, 0x6f746f67 # goto
-	sw t0, 12(sp)
-	mv a0, s1
-	addi a1, sp, 12
-	li a2, 4
-	call _memcmp
-	beqz a0, .Lcompile_line_goto
-
-	li t0, 0x6e72 # rn
-	sw t0, 12(sp)
-	li t0, 0x75746572 # retu
-	sw t0, 8(sp)
-	mv a0, s1
-	addi a1, sp, 8
-	li a2, 6
-	call _memcmp
-	beqz a0, .Lcompile_line_return
-
-	li t0, 0x6669 # if
-	sw t0, 12(sp)
-	mv a0, s1
-	addi a1, sp, 12
-	li a2, 2
-	call _memcmp
-	beqz a0, .Lcompile_line_if
-
-	lbu t0, (s1)
-	li t1, '.'
-	beq t0, t1, .Lcompile_line_label
-	li t1, '_'
-	beq t0, t1, .Lcompile_line_identifier
+	if loca84 = 0 then
+		goto .Lcompile_line_empty (* Skip an empty line. *)
+	end
+
+	loca16 := _current()
+	loca0 := _front(loca16)
+	(* ( *)
+	if loca0 = 0x28 then
+		goto .Lcompile_line_comment
+	end
+	loca16 := _current()
+
+	loca12 := 0x676f7270 (* prog *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_program
+	end
+
+	loca12 := 0x736e6f63 (* cons *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_const
+	end
+
+	loca12 := 0x0a726176 (* var\n *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_var
+	end
+
+	loca12 := 0x636f7270 (* proc *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_procedure
+	end
+
+	loca12 := 0x69676562 (* begi *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_begin
+	end
+
+	loca12 := 0x2e646e65 (* end. *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_exit
+	end
+
+	loca12 := 0x61636f6c (* loca *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_identifier
+	end
+
+	loca12 := 0x6f706d69 (* impo *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_import
+	end
+
+	loca12 := 0x6f746f67 (* goto *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_goto
+	end
+
+	loca12 := 0x75746572 (* retu *)
+	loca4 := _memcmp(loca16, @loca12, 4)
+	if loca4 = 0 then
+		goto .Lcompile_line_return
+	end
 
+	loca12 := 0x6669 (* if *)
+	loca4 := _memcmp(loca16, @loca12, 2)
+	if loca4 = 0 then
+		goto .Lcompile_line_if
+	end
+
+	(* . *)
+	if loca0 = 0x2e then
+		goto .Lcompile_line_label
+	end
+	(* _ *)
+	if loca0 = 0x5f then
+		goto .Lcompile_line_identifier
+	end
 	goto .Lcompile_line_unchanged (* Else. *)
 
 	.Lcompile_line_if:
@@ -1326,10 +1382,6 @@ begin
 	goto .Lcompile_line_section
 
 	.Lcompile_line_return
-	(* DEBUG
-	mv a0, s1
-	li a1, 8
-	call _write_error *)
 	_compile_return()
 	goto .Lcompile_line_section
 
@@ -1350,12 +1402,14 @@ begin
 	goto .Lcompile_line_section
 
 	.Lcompile_line_begin
-	lw a1, 80(sp)
-	bnez a1, .Lcompile_line_compile_entry
+
+	if loca80 = 1 then
+		goto .Lcompile_line_compile_entry
+	end
 	_compile_text_section()
 	.Lcompile_line_compile_entry
 	_compile_entry_point()
-	li a0, 1
+	loca8 := 1
 	goto .Lcompile_line_end
 
 	.Lcompile_line_const
@@ -1363,12 +1417,13 @@ begin
 	goto .Lcompile_line_section
 
 	.Lcompile_line_procedure
-	lw a1, 80(sp)
-	bnez a1, .Lcompile_line_compile_procedure
+	if loca80 = 1 then
+		goto .Lcompile_line_compile_procedure
+	end
 	_compile_text_section()
 	.Lcompile_line_compile_procedure
 	_compile_procedure()
-	li a0, 1
+	loca8 := 1
 	goto .Lcompile_line_end
 
 	.Lcompile_line_var
@@ -1392,13 +1447,13 @@ begin
 	goto .Lcompile_line_section
 
 	.Lcompile_line_section
-	mv a0, zero
+	loca8 := 0
 
 	.Lcompile_line_end
-	sw a0, 12(sp)
 	_skip_spaces()
 	_skip_comment()
-	lw a0, 12(sp)
+
+	return loca8
 end
 
 (* Prints ".section .text" and exits. *)
@@ -1443,11 +1498,9 @@ end
 proc _compile_exit()
 var loca0: Word
 begin
-	(*
-	li a0, 0
-	li a7, SYS_EXIT
-	ecall
-	*)
+	(* li a0, 0 *)
+	(* li a7, SYS_EXIT *)
+	(* ecall *)
 	loca0 := 0x6120696c (* li a *)
 	_write_out(@loca0, 4)
 	loca0 := 0x30202c30 (* 0, 0 *)
@@ -1469,16 +1522,20 @@ end
 
 (* Finds the end of the line and returns its length in a0. *)
 proc _read_line()
+var
+	loca0: ^Byte
+	loca4: Byte
 begin
 	loca0 := _current() (* Local position in the source text. *)
 
 	.Lread_line_do
-	lw t0, 0(sp)
-	lbu t1, (t0) # t1 = Current character.
-	beqz t1, .Lread_line_end # Exit the loop on the NUL character.
-	li t2, '\n'
-	beq t1, t2, .Lread_line_end # Exit the loop on the new line.
-
+	loca4 := _front(loca0) (* t1 = Current character. *)
+	if loca4 = 0 then
+		goto .Lread_line_end (* Exit the loop on the NUL character. *)
+	end
+	if loca4 = 0x0a then
+		goto .Lread_line_end (* Exit the loop on the new line. *)
+	end
 	loca0 := loca0 + 1
 	goto .Lread_line_do
 
@@ -1491,18 +1548,26 @@ proc _compile()
 var
 	loca0, loca4: Word
 	loca8: Bool
+	loca12: Char
+	loca16: ^Byte
 begin
 	loca4 := 0 (* Whether the text section header was already emitted. *)
 
 	.Lcompile_do
-	lbu t0, (s1) # t0 = Current character.
-	beqz t0, .Lcompile_end # Exit the loop on the NUL character.
+	loca16 := _current()
+	loca12 := _front(loca16) (* t0 = Current character. *)
 
-	_skip_indentation()
+	if loca12 = 0 then
+		goto .Lcompile_end (* Exit the loop on the NUL character. *)
+	end
+
+	_skip_spaces()
 	loca0 := _read_line()
 	loca8 := _compile_line(loca0, loca4)
 
-	beqz a0, .Lcompile_do
+	if loca8 = 0 then
+		goto .Lcompile_do
+	end
 	(* Update whether the text section header was already emitted. *)
 	loca4 := loca4 or loca8
 
@@ -1513,30 +1578,35 @@ end
 (* Returns the pointer to the current position in the source text in a0. *)
 proc _current()
 begin
-	mv a0, s1
+	return s1
 end
 
 (* a0 is the number of bytes to advance in the source text. *)
-proc _advance()
+proc _advance(loca84: Word)
 begin
 	add s1, s1, a0
 end
 
-(* Returns the first character in the remaining source text. *)
-proc _front()
+(*
+a0 - Pointer to an array to get the first element.
+
+Returns the first character in the remaining source text.
+*)
+proc _front(loca84: ^Word)
 begin
-	lbu a0, (s1)
+	return _get(loca84) & 0xff
 end
 
-(* Entry point. *)
+proc _main()
 begin
 	(* Read the source from the standard input. *)
-	la a0, source_code
-	la a1, SOURCE_BUFFER_SIZE # Buffer size.
-	lw a1, (a1)
-	call _read_file
+	_read_file(source_code, SOURCE_BUFFER_SIZE)
+
+	addi s2, zero, 1
+end
 
-	la s1, source_code # s1 = Source code position.
-	li s2, 1
+(* Entry point. *)
+begin
+	_main()
 	_compile()
 end.
diff --git a/boot/states.txt b/boot/states.txt
new file mode 100644
index 0000000..20d5966
--- /dev/null
+++ b/boot/states.txt
@@ -0,0 +1,20 @@
+- start
+digit: integer
+upper: identifier
+lower: identifier
+space: start
+invalid: error
+
+- identifier
+digit: identifier
+upper: identifier
+lower: identifier
+space: end
+invalid: end
+
+- integer:
+digit: integer
+upper: end
+lower: end
+space: end
+invalid: end
diff --git a/boot/tokenizer.s b/boot/tokenizer.s
new file mode 100644
index 0000000..2057c2e
--- /dev/null
+++ b/boot/tokenizer.s
@@ -0,0 +1,181 @@
+.global _tokenizer_initialize
+
+.section .rodata
+
+raw_classes:
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "space\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "digit\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "upper\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "lower\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+	.ascii "invalid\n"
+
+.section .bss
+.type class_names, @object
+.size class_names, 1024
+class_names: .zero 1024
+
+.section .data
+.type classes, @object
+.size classes, 512 # 128 characters * 4 byte.
+classes:
+
+.section .text
+
+# Initializes the classification table.
+#
+# Paramaters:
+# a0 - Raw input for the classification table.
+.type _tokenizer_classes, @function
+_tokenizer_classes:
+	# Prologue.
+	addi sp, sp, -8
+	sw ra, 4(sp)
+	sw s0, 0(sp)
+	addi s0, sp, 8
+
+	# Epilogue.
+	lw ra, 4(sp)
+	lw s0, 0(sp)
+	addi sp, sp, 8
+	ret
+
+# Initializes the lookup tables.
+.type _tokenizer_initialize, @function
+_tokenizer_initialize:
+	# Prologue.
+	addi sp, sp, -8
+	sw ra, 4(sp)
+	sw s0, 0(sp)
+	addi s0, sp, 8
+
+	la a0, raw_classes
+	call _tokenizer_classes
+
+	# Epilogue.
+	lw ra, 4(sp)
+	lw s0, 0(sp)
+	addi sp, sp, 8
+	ret