Move stages into subdirectories

1 files changed, 1129 insertions, 0 deletions

diff --git a/boot/stage4/cl.elna b/boot/stage4/cl.elna
new file mode 100644
index 0000000..d873b9a
--- /dev/null
+++ b/boot/stage4/cl.elna
@@ -0,0 +1,1129 @@
+# This Source Code Form is subject to the terms of the Mozilla Public License,
+# 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 4 compiler.
+#
+# - Taking value of local and global variables. Variables that doesn't begin
+#   with "v" are considered global.
+# - Simple variable assignment, e.g. v0 := 5 or v0 := global_variable;
+#   7 words on the stack, 28 - 56, are reversed for procedure arguments (caller side).
+# - Take address unary operation "@".
+
+.section .rodata
+
+.type keyword_section, @object
+keyword_section: .ascii ".section"
+
+.type keyword_type, @object
+keyword_type: .ascii ".type"
+
+.type keyword_ret, @object
+keyword_ret: .ascii "ret"
+
+.type keyword_global, @object
+keyword_global: .ascii ".globl"
+
+.type keyword_proc, @object
+keyword_proc: .ascii "proc "
+
+.type keyword_end, @object
+keyword_end: .ascii "end"
+
+.type keyword_begin, @object
+keyword_begin: .ascii "begin"
+
+.type keyword_var, @object
+keyword_var: .ascii "var"
+
+.type asm_prologue, @object
+asm_prologue: .string "\taddi sp, sp, -64\n\tsw ra, 60(sp)\n\tsw s0, 56(sp)\n\taddi s0, sp, 64\n"
+
+.type asm_epilogue, @object
+asm_epilogue: .string "\tlw ra, 60(sp)\n\tlw s0, 56(sp)\n\taddi sp, sp, 64\n\tret\n"
+
+.type asm_type_directive, @object
+asm_type_directive: .string ".type "
+
+.type asm_type_function, @object
+asm_type_function: .string ", @function\n"
+
+.type asm_colon, @object
+asm_colon: .string ":\n"
+
+.type asm_call, @object
+asm_call: .string "\tcall "
+
+.type asm_j, @object
+asm_j: .string "\tj "
+
+.type asm_li, @object
+asm_li: .string "\tli "
+
+.type asm_lw, @object
+asm_lw: .string "\tlw "
+
+.type asm_la, @object
+asm_la: .string "\tla "
+
+.type asm_sw, @object
+asm_sw: .string "\tsw "
+
+.type asm_addi, @object
+asm_addi: .string "\taddi "
+
+.type asm_t0, @object
+asm_t0: .string "t0"
+
+.type asm_t1, @object
+asm_t1: .string "t1"
+
+.type asm_comma, @object
+asm_comma: .string ", "
+
+.type asm_sp, @object
+asm_sp: .string "sp"
+
+.section .bss
+
+# When modifiying also change the read size in the entry point procedure.
+.type source_code, @object
+source_code: .zero 81920
+
+.section .data
+
+.type source_code_position, @object
+source_code_position: .word source_code
+
+.section .text
+
+# Reads standard input into a buffer.
+# a0 - Buffer pointer.
+# a1 - Buffer size.
+#
+# Returns the amount of bytes written in a0.
+proc _read_file();
+begin
+	mv a2, a1
+	mv a1, a0
+	# STDIN.
+	li a0, 0
+	li a7, 63 # SYS_READ.
+	ecall
+end;
+
+# Writes to the standard output.
+#
+# Parameters:
+# a0 - Buffer.
+# a1 - Buffer length.
+proc _write_s();
+begin
+	mv a2, a1
+	mv a1, a0
+	# STDOUT.
+	li a0, 1
+	li a7, 64 # SYS_WRITE.
+	ecall
+end;
+
+# Writes a number to a string buffer.
+#
+# t0 - Local buffer.
+# t1 - Constant 10.
+# t2 - Current character.
+# t3 - Whether the number is negative.
+#
+# Parameters:
+# a0 - Whole number.
+# a1 - Buffer pointer.
+#
+# Sets a0 to the length of the written number.
+proc _print_i();
+begin
+	li t1, 10
+	addi t0, s0, -9
+
+	li t3, 0
+	bgez a0, .print_i_digit10
+	li t3, 1
+	neg a0, a0
+
+.print_i_digit10:
+	rem t2, a0, t1
+	addi t2, t2, '0'
+	sb t2, 0(t0)
+	div a0, a0, t1
+	addi t0, t0, -1
+	bne zero, a0, .print_i_digit10
+
+	beq zero, t3, .print_i_write_call
+	addi t2, zero, '-'
+	sb t2, 0(t0)
+	addi t0, t0, -1
+
+.print_i_write_call:
+	mv a0, a1
+	addi a1, t0, 1
+	sub a2, s0, t0
+	addi a2, a2, -9
+	sw a2, 0(sp)
+
+	_memcpy();
+
+	lw a0, 0(sp)
+end;
+
+# Writes a number to the standard output.
+#
+# Parameters:
+# a0 - Whole number.
+proc _write_i();
+begin
+	addi a1, sp, 0
+	_print_i();
+
+	mv a1, a0
+	addi a0, sp, 0
+	_write_s();
+
+end;
+
+# Writes a character from a0 into the standard output.
+proc _write_c();
+begin
+	sb a0, 0(sp)
+	addi a0, sp, 0
+	li a1, 1
+	_write_s();
+end;
+
+# Write null terminated string.
+#
+# Parameters:
+# a0 - String.
+proc _write_z();
+begin
+	sw a0, 0(sp)
+
+.write_z_loop:
+	# Check for 0 character.
+	lb a0, (a0)
+	beqz a0, .write_z_end
+
+	# Print a character.
+	lw a0, 0(sp)
+	lb a0, (a0)
+	_write_c();
+
+	# Advance the input string by one byte.
+	lw a0, 0(sp)
+	addi a0, a0, 1
+	sw a0, 0(sp)
+
+	goto .write_z_loop;
+
+.write_z_end:
+end;
+
+# Detects if a0 is an uppercase character. Sets a0 to 1 if so, otherwise to 0.
+proc _is_upper();
+begin
+	li t0, 'A' - 1
+	sltu t1, t0, a0 # t1 = a0 >= 'A'
+
+	sltiu t2, a0, 'Z' + 1 # t2 = a0 <= 'Z'
+	and a0, t1, t2 # t1 = a0 >= 'A' & a0 <= 'Z'
+end;
+
+# Detects if a0 is an lowercase character. Sets a0 to 1 if so, otherwise to 0.
+proc _is_lower();
+begin
+	li t0, 'a' - 1
+	sltu t2, t0, a0 # t2 = a0 >= 'a'
+
+	sltiu t3, a0, 'z' + 1 # t3 = a0 <= 'z'
+	and a0, t2, t3 # t2 = a0 >= 'a' & a0 <= 'z'
+end;
+
+# Detects if the passed character is a 7-bit alpha character or an underscore.
+#
+# Paramters:
+# a0 - Tested character.
+#
+# Sets a0 to 1 if the character is an alpha character or underscore, sets it to 0 otherwise.
+proc _is_alpha();
+begin
+	sw a0, 0(sp)
+
+	_is_upper();
+	sw a0, 4(sp)
+
+	_is_lower(v0);
+
+	lw t0, 0(sp)
+	xori t1, t0, '_'
+	seqz t1, t1
+
+	lw t0, 4(sp)
+	or a0, a0, t0
+	or a0, a0, t1
+end;
+
+# Detects whether the passed character is a digit
+# (a value between 0 and 9).
+#
+# Parameters:
+# a0 - Exemined value.
+#
+# Sets a0 to 1 if it is a digit, to 0 otherwise.
+proc _is_digit();
+begin
+	li t0, '0' - 1
+	sltu t1, t0, a0 # t1 = a0 >= '0'
+
+	sltiu t2, a0, '9' + 1 # t2 = a0 <= '9'
+
+	and a0, t1, t2
+end;
+
+proc _is_alnum();
+begin
+	sw a0, 4(sp)
+
+	_is_alpha();
+	sw a0, 0(sp)
+
+	_is_digit(v4);
+
+	lw a1, 0(sp)
+	or a0, a0, a1
+end;
+
+# Reads the next token.
+#
+# Returns token length in a0.
+proc _read_token();
+begin
+	la t0, source_code_position # Token pointer.
+	lw t0, (t0)
+	sw t0, 0(sp) # Current token position.
+	sw zero, 4(sp) # Token length.
+
+.read_token_loop:
+	lb t0, (t0) # Current character.
+
+	# First we try to read a derictive.
+	# A derictive can contain a dot and characters.
+	li t1, '.'
+	beq t0, t1, .read_token_next
+
+	lw a0, 0(sp)
+	lb a0, (a0)
+	_is_alnum();
+	bnez a0, .read_token_next
+
+	goto .read_token_end;
+
+.read_token_next:
+	# Advance the source code position and token length.
+	lw t0, 4(sp)
+	addi t0, t0, 1
+	sw t0, 4(sp)
+
+	lw t0, 0(sp)
+	addi t0, t0, 1
+	sw t0, 0(sp)
+
+	goto .read_token_loop;
+
+.read_token_end:
+	lw a0, 4(sp)
+end;
+
+# a0 - First pointer.
+# a1 - Second pointer.
+# a2 - The length to compare.
+#
+# Returns 0 in a0 if memory regions are equal.
+proc _memcmp();
+begin
+	mv t0, a0
+	li a0, 0
+
+.memcmp_loop:
+	beqz a2, .memcmp_end
+
+	lbu t1, (t0)
+	lbu t2, (a1)
+	sub a0, t1, t2
+
+	bnez a0, .memcmp_end
+
+	addi t0, t0, 1
+	addi a1, a1, 1
+	addi a2, a2, -1
+
+	goto .memcmp_loop;
+
+.memcmp_end:
+end;
+
+# Copies memory.
+#
+# Parameters:
+# a0 - Destination.
+# a1 - Source.
+# a2 - Size.
+#
+# Preserves a0.
+proc _memcpy();
+begin
+	mv t0, a0
+
+.memcpy_loop:
+	beqz a2, .memcpy_end
+
+	lbu t1, (a1)
+	sb t1, (a0)
+
+	addi a0, a0, 1
+	addi a1, a1, 1
+	addi a2, a2, -1
+
+	goto .memcpy_loop
+
+.memcpy_end:
+	mv a0, t0
+end;
+
+# Advances the token stream by a0 bytes.
+proc _advance_token();
+begin
+	la t0, source_code_position
+	lw t1, (t0)
+	add t1, t1, a0
+	sw t1, (t0)
+end;
+
+# Prints the current token.
+#
+# Parameters:
+# a0 - Token length.
+#
+# Returns a0 unchanged.
+proc _write_token();
+begin
+	sw a0, 0(sp)
+
+	la a0, source_code_position
+	lw a0, (a0)
+	lw a1, 0(sp)
+	_write_s();
+
+	lw a0, 0(sp)
+end;
+
+proc _compile_section();
+begin
+	# Print and skip the ".section" (8 characters) directive and a space after it.
+	_write_token(9);
+	_advance_token();
+
+	# Read the section name.
+	_read_token();
+	addi a0, a0, 1
+
+	_write_token();
+	_advance_token();
+end;
+
+# Prints and skips a line.
+proc _skip_comment();
+begin
+	la t0, source_code_position
+	lw t1, (t0)
+
+.skip_comment_loop:
+	# Check for newline character.
+	lb t2, (t1)
+	li t3, '\n'
+	beq t2, t3, .skip_comment_end
+
+	# Advance the input string by one byte.
+	addi t1, t1, 1
+	sw t1, (t0)
+
+	goto .skip_comment_loop;
+
+.skip_comment_end:
+	# Skip the newline.
+	addi t1, t1, 1
+	sw t1, (t0)
+end;
+
+# Prints and skips a line.
+proc _compile_line();
+begin
+.compile_line_loop:
+	la a0, source_code_position
+	lw a1, (a0)
+
+	lb t0, (a1)
+	li t1, '\n'
+	beq t0, t1, .compile_line_end
+
+	# Print a character.
+	lw a0, (a1)
+	_write_c();
+
+	# Advance the input string by one byte.
+	_advance_token(1);
+
+	goto .compile_line_loop;
+
+.compile_line_end:
+	_write_c('\n');
+
+	_advance_token(1);
+end;
+
+proc _compile_integer_literal();
+begin
+	la a0, asm_li
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_read_token();
+	_write_token();
+	_advance_token();
+
+	_write_c('\n');
+end;
+
+proc _compile_character_literal();
+begin
+	la a0, asm_li
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_write_c('\'');
+	_advance_token(1);
+
+	la t0, source_code_position
+	lw t0, (t0)
+	lb a0, (t0)
+	li t1, '\\'
+	bne a0, t1, .compile_character_literal_end
+	
+	_write_c('\\');
+	_advance_token(1);
+
+.compile_character_literal_end:
+	la t0, source_code_position
+	lw t0, (t0)
+	lb a0, (t0)
+	_write_c();
+
+	_write_c('\'');
+	_write_c('\n');
+
+	_advance_token(2);
+
+end;
+
+proc _compile_variable_expression();
+begin
+	_compile_designator();
+
+	la a0, asm_lw
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_write_c('(');
+	la a0, asm_t0
+	_write_z();
+
+	_write_c(')');
+	_write_c('\n');
+
+end;
+
+proc _compile_address_expression();
+begin
+	# Skip the "@" sign.
+	_advance_token(1);
+	_compile_designator();
+
+end;
+
+proc _compile_expression();
+begin
+	la t0, source_code_position
+	lw t0, (t0)
+	lb a0, (t0)
+	sw a0, 0(sp)
+
+	li t1, '\''
+	beq a0, t1, .compile_expression_character_literal
+
+	li t1, '@'
+	beq a0, t1, .compile_expression_address
+
+	_is_digit(v0);
+	bnez a0, .compile_expression_integer_literal
+
+	goto .compile_expression_variable;
+
+.compile_expression_character_literal:
+	_compile_character_literal();
+	goto .compile_expression_end;
+
+.compile_expression_integer_literal:
+	_compile_integer_literal();
+	goto .compile_expression_end;
+
+.compile_expression_address:
+	_compile_address_expression();
+	goto .compile_expression_end;
+
+.compile_expression_variable:
+	_compile_variable_expression();
+	goto .compile_expression_end;
+
+.compile_expression_end:
+end;
+
+proc _compile_call();
+begin
+	# Stack variables:
+	# v0 - Procedure name length.
+	# v4 - Procedure name pointer. 
+	# v8 - Argument count.
+
+	_read_token();
+	sw a0, 0(sp)
+	la t0, source_code_position
+	lw t0, (t0)
+	sw t0, 4(sp)
+
+	sw zero, 8(sp)
+
+	# Skip the identifier and left paren.
+	addi a0, a0, 1
+	_advance_token();
+
+	la t0, source_code_position
+	lw t0, (t0)
+	lb t0, (t0)
+
+	li t1, ')'
+	beq t0, t1, .compile_call_finalize
+
+.compile_call_loop:
+	_compile_expression();
+
+	# Save the argument on the stack.
+	la a0, asm_sw
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	# Calculate the stack offset: 52 - (4 * argument_counter)
+	lw t0, 8(sp)
+	li t1, 4
+	mul t0, t0, t1
+	li t1, 52
+	sub a0, t1, t0
+	_write_i();
+
+	_write_c('(')
+	la a0, asm_sp
+	_write_z();
+	_write_c(')')
+
+	_write_c('\n');
+
+	# Add one to the argument counter.
+	lw t0, 8(sp)
+	addi t0, t0, 1
+	sw t0, 8(sp)
+
+	la t0, source_code_position
+	lw t0, (t0)
+	lb t0, (t0)
+
+	li t1, ','
+	bne t0, t1, .compile_call_finalize
+
+	_advance_token(2);
+	goto .compile_call_loop;
+
+.compile_call_finalize:
+	# Load the argument from the stack.
+
+	lw t0, 8(sp)
+	beqz t0, .compile_call_end
+
+	# Decrement the argument counter.
+	lw t0, 8(sp)
+	addi t0, t0, -1
+	sw t0, 8(sp)
+
+	la a0, asm_lw
+	_write_z();
+
+	_write_c('a');
+	lw a0, 8(sp)
+	_write_i();
+
+	la a0, asm_comma
+	_write_z();
+
+	# Calculate the stack offset: 52 - (4 * argument_counter)
+	lw t0, 8(sp)
+	li t1, 4
+	mul t0, t0, t1
+	li t1, 52
+	sub a0, t1, t0
+	_write_i();
+
+	_write_c('(');
+	la a0, asm_sp
+	_write_z();
+
+	_write_c(')');
+	_write_c('\n');
+
+	goto .compile_call_finalize;
+
+.compile_call_end:
+	la a0, asm_call
+	_write_z();
+
+	_write_s(v4, v0);
+
+	# Skip the right paren.
+	_advance_token(1);
+end;
+
+proc _compile_goto();
+begin
+	_advance_token(5);
+
+	_read_token();
+	sw a0, 0(sp)
+
+	la a0, asm_j
+	_write_z();
+
+	_write_token(v0);
+	_advance_token();
+end;
+
+proc _compile_local_designator();
+begin
+	# Skip "v" in the local variable name.
+	_advance_token(1);
+
+	la a0, asm_addi
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	la a0, asm_sp
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	# Read local variable stack offset and save it.
+	la t0, source_code_position
+	lw t0, (t0)
+	sw t0, 0(sp)
+
+	_read_token();
+	sw a0, 4(sp)
+
+	_write_token();
+	_advance_token();
+
+	_write_c('\n');
+
+end;
+
+proc _compile_global_designator();
+begin
+	la a0, asm_la
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_read_token();
+	_write_token();
+	_advance_token();
+
+	_write_c('\n');
+
+end;
+
+proc _compile_designator();
+begin
+	la t0, source_code_position
+	lw t0, (t0)
+	lb a0, (t0)
+
+	li t1, 'v'
+	beq a0, t1, .compile_designator_local
+
+	goto .compile_designator_global;
+
+.compile_designator_local:
+	_compile_local_designator();
+	goto .compile_designator_end;
+
+.compile_designator_global:
+	_compile_global_designator();
+	goto .compile_designator_end;
+
+.compile_designator_end:
+end;
+
+proc _compile_assignment();
+begin
+	_compile_designator();
+
+	# Save the assignee address on the stack.
+	la a0, asm_sw
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_write_i(20);
+	_write_c('(');
+	la a0, asm_sp
+	_write_z();
+	_write_c(')');
+	_write_c('\n');
+	# Skip the assignment sign (:=) with surrounding whitespaces.
+	_advance_token(4);
+
+	# Compile the assignment.
+	_compile_expression();
+
+	la a0, asm_lw
+	_write_z();
+
+	la a0, asm_t1
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_write_i(20);
+	_write_c('(');
+	la a0, asm_sp
+	_write_z();
+	_write_c(')');
+	_write_c('\n');
+
+	la a0, asm_sw
+	_write_z();
+
+	la a0, asm_t0
+	_write_z();
+
+	la a0, asm_comma
+	_write_z();
+
+	_write_c('(');
+	la a0, asm_t1
+	_write_z();
+	_write_c(')');
+end;
+
+proc _compile_statement();
+begin
+	# 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
+	lb t0, (t0)
+	
+	li t1, '_'
+	beq t0, t1, .compile_statement_call
+
+	li t1, 'g'
+	beq t0, t1, .compile_statement_goto
+
+	li t1, 'v'
+	beq t0, t1, .compile_statement_assignment
+
+	_compile_line();
+	goto .compile_statement_end;
+
+.compile_statement_call:
+	_advance_token(1);
+	_compile_call();
+
+	goto .compile_statement_semicolon;
+
+.compile_statement_goto:
+	_advance_token(1);
+	_compile_goto();
+
+	goto .compile_statement_semicolon;
+
+.compile_statement_assignment:
+	_advance_token(1);
+	_compile_assignment();
+
+	goto .compile_statement_semicolon;
+
+.compile_statement_semicolon:
+	_advance_token(2);
+
+	_write_c('\n');
+
+.compile_statement_end:
+end;
+
+proc _compile_procedure_body();
+begin
+.compile_procedure_body_loop:
+	la a0, source_code_position
+	lw a0, (a0)
+	la a1, keyword_end
+	li a2, 3 # "end" length.
+	_memcmp();
+
+	beqz a0, .compile_procedure_body_epilogue
+
+	_compile_statement();
+	goto .compile_procedure_body_loop;
+
+.compile_procedure_body_epilogue:
+end;
+
+proc _compile_procedure();
+begin
+	# Skip "proc ".
+	_advance_token(5);
+
+	_read_token();
+	sw a0, 0(sp) # Save the procedure name length.
+
+	# Write .type _procedure_name, @function.
+	la a0, asm_type_directive
+	_write_z();
+
+	_write_token(v0);
+
+	la a0, asm_type_function
+	_write_z();
+
+	# Write procedure label, _procedure_name:
+	_write_token(v0);
+
+	la a0, asm_colon
+	_write_z();
+
+	# Skip the function name and trailing parens, semicolon, "begin" and newline.
+	lw a0, 0(sp)
+	addi a0, a0, 10
+	_advance_token();
+
+	la a0, asm_prologue
+	_write_z();
+
+	_compile_procedure_body();
+
+	# Write the epilogue.
+	la a0, asm_epilogue
+	_write_z();
+
+	# Skip the "end" keyword, semicolon and newline.
+	_advance_token(5);
+end;
+
+proc _compile_type();
+begin
+	# Print and skip the ".type" (5 characters) directive and a space after it.
+	_write_token(6);
+	_advance_token();
+
+	# Read and print the symbol name.
+	_read_token();
+
+	# Print and skip the symbol name, comma, space and @.
+	addi a0, a0, 3
+	_write_token();
+	_advance_token();
+
+	# Read the symbol type.
+	_read_token();
+	la t0, source_code_position
+	lw t0, (t0)
+	sw t0, 12(sp)
+
+	# Print the symbol type and newline.
+	addi a0, a0, 1
+	_write_token();
+	_advance_token();
+
+	# Write the object definition itself.
+	_compile_line();
+
+.compile_type_end:
+end;
+
+proc _skip_newlines();
+begin
+	# Skip newlines.
+	la t0, source_code_position
+	lw t1, (t0)
+
+.skip_newlines_loop:
+	lb t2, (t1)
+	li t3, '\n'
+	bne t2, t3, .skip_newlines_end
+	beqz t2, .skip_newlines_end
+
+	addi t1, t1, 1
+	sw t1, (t0)
+
+	goto .skip_newlines_loop;
+
+.skip_newlines_end:
+end;
+
+# Process the source code and print the generated code.
+proc _compile();
+begin
+.compile_loop:
+	_skip_newlines();
+
+	la t0, source_code_position
+	lw t0, (t0)
+	lb t0, (t0)
+	beqz t0, .compile_end
+	li t1, '#'
+	beq t0, t1, .compile_comment
+
+	la a0, source_code_position
+	lw a0, (a0)
+	la a1, keyword_section
+	li a2, 8 # ".section" length.
+	_memcmp();
+
+	beqz a0, .compile_section
+
+	la a0, source_code_position
+	lw a0, (a0)
+	la a1, keyword_type
+	li a2, 5 # ".type" length.
+	_memcmp();
+
+	beqz a0, .compile_type
+
+	la a0, source_code_position
+	lw a0, (a0)
+	la a1, keyword_proc
+	li a2, 5 # "proc " length. Space is needed to distinguish from "procedure".
+	_memcmp();
+
+	beqz a0, .compile_procedure
+
+	la a0, source_code_position
+	lw a0, (a0)
+	la a1, keyword_global
+	li a2, 6 # ".globl" length.
+	_memcmp();
+
+	beqz a0, .compile_global
+	# Not a known token, exit.
+	goto .compile_end;
+
+.compile_section:
+	_compile_section();
+
+	goto .compile_loop;
+
+.compile_type:
+	_compile_type();
+
+	goto .compile_loop;
+
+.compile_global:
+	_compile_line();
+
+	goto .compile_loop;
+
+.compile_comment:
+	_skip_comment();
+
+	goto .compile_loop;
+
+.compile_procedure:
+	_compile_procedure();
+
+	goto .compile_loop;
+
+.compile_end:
+end;
+
+# Terminates the program. a0 contains the return code.
+#
+# Parameters:
+# a0 - Status code.
+proc _exit();
+begin
+	li a7, 93 # SYS_EXIT
+	ecall
+end;
+
+# Entry point.
+.globl _start
+proc _start();
+begin
+	# Read the source from the standard input.
+	la a0, source_code
+	li a1, 81920 # Buffer size.
+	_read_file();
+	_compile();
+
+	_exit(0);
+
+end;