# 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/.

.global _start # Program entry point.

#
# Registers used as global variables:
# s1 - Contains the current position in the source text.
# s2 - Label counter.
#
# - The compiler expects valid input, otherwise it will generate invalid
# assembly or hang. There is no error checking, no semantic analysis, no
# type checking.
#
# - Imports with only a module name without package, e.g.
# "import dummy", can be parsed, but are ignored.
#
# - No loops. Only labels and goto.
#
# - Only unsigned number literals are supported (in decimal or
# hexadecimal format).
#
# - Comments are accepted only at the end of a line.
#
# - Return can be used only as the last statement of a procedure. It
# doesn't actually return, but sets a0 to the appropriate value.
#
# - The lvalue of an assignment can only be an identifier.

.include "boot/definitions.inc"

.equ SOURCE_BUFFER_SIZE, 81920

.section .rodata
section_rodata: .ascii ".section .rodata\n"
.equ SECTION_RODATA_SIZE, . - section_rodata
section_text: .ascii ".section .text\n"
.equ SECTION_TEXT_SIZE, . - section_text
section_bss: .ascii ".section .bss\n"
.equ SECTION_BSS_SIZE, . - section_bss
global_start: .ascii ".global _start\n"
.equ GLOBAL_START_SIZE, . - global_start
prologue: .ascii "addi sp, sp, -96\nsw ra, 92(sp)\nsw s0, 88(sp)\naddi s0, sp, 96\n"
.equ PROLOGUE_SIZE, . - prologue
epilogue: .ascii "lw ra, 92(sp)\nlw s0, 88(sp)\naddi sp, sp, 96\nret\n"
.equ EPILOGUE_SIZE, . - epilogue

asm_exit: .ascii "li a0, 0\nli a7, 93\necall\n"
.equ ASM_EXIT_SIZE, . - asm_exit
asm_start: .ascii ".type _start, @function\n_start:\n"
.equ ASM_START_SIZE, . - asm_start
asm_and_a0_a1: .ascii "and a0, a0, a1\n"
.equ ASM_AND_A0_A1_SIZE, . - asm_and_a0_a1
asm_or_a0_a1: .ascii "or a0, a0, a1\n"
.equ ASM_OR_A0_A1_SIZE, . - asm_or_a0_a1
asm_add_a0_a1: .ascii "add a0, a0, a1\n"
.equ ASM_ADD_A0_A1_SIZE, . - asm_add_a0_a1
asm_sub_a0_a1: .ascii "sub a0, a0, a1\n"
.equ ASM_SUB_A0_A1_SIZE, . - asm_sub_a0_a1
asm_mul_a0_a1: .ascii "mul a0, a0, a1\n"
.equ ASM_MUL_A0_A1_SIZE, . - asm_mul_a0_a1
asm_seqz_a0: .ascii "seqz a0, a0\n"
.equ ASM_SEQZ_A0_SIZE, . - asm_seqz_a0
asm_neg_a0: .ascii "neg a0, a0\n"
.equ ASM_NEG_A0_SIZE, . - asm_neg_a0
asm_type: .ascii ".type "
.equ ASM_TYPE_SIZE, . - asm_type
asm_type_function: .ascii ", @function\n"
.equ ASM_TYPE_FUNCTION_SIZE, . - asm_type_function
asm_type_object: .ascii ", @object\n"
.equ ASM_TYPE_OBJECT_SIZE, . - asm_type_object
asm_restore_parameters:
	.ascii "lw a0, 60(sp)\nlw a1, 56(sp)\nlw a2, 52(sp)\nlw a3, 48(sp)\nlw a4, 44(sp)\nlw a5, 40(sp)\n"
.equ ASM_RESTORE_PARAMETERS_SIZE, . - asm_restore_parameters
asm_preserve_parameters:
	.ascii "sw a0, 84(sp)\nsw a1, 80(sp)\nsw a2, 76(sp)\nsw a2, 76(sp)\nsw a3, 72(sp)\nsw a4, 68(sp)\nsw a5, 64(sp)\n"
.equ ASM_PRESERVE_PARAMETERS_SIZE, . - asm_preserve_parameters

.section .bss
.type source_code, @object
source_code: .zero SOURCE_BUFFER_SIZE

.section .text

# Ignores the import.
.type _compile_import, @function
_compile_import:
	# Prologue.
	addi sp, sp, -24
	sw ra, 20(sp)
	sw s0, 16(sp)
	addi s0, sp, 24

.Lcompile_import_loop:
	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next
	li t0, TOKEN_IMPORT
	lw t1, 0(sp)
	bne t0, t1, .Lcompile_import_end
	# a0 is set from the previous _tokenize_next call. Skip the module name.
	addi a1, sp, 0
	call _tokenize_next
	mv s1, a0

	j .Lcompile_import_loop

.Lcompile_import_end:
	# Epilogue.
	lw ra, 20(sp)
	lw s0, 16(sp)
	addi sp, sp, 24
	ret

.type _build_binary_expression, @function
_build_binary_expression:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	li a0, 0
	call _build_expression

	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next
	lw t0, 12(sp)

	li t1, TOKEN_AND
	beq t0, t1, .Lbuild_binary_expression_and

	li t1, TOKEN_OR
	beq t0, t1, .Lbuild_binary_expression_or

	li t1, TOKEN_PLUS
	beq t0, t1, .Lbuild_binary_expression_plus

	li t1, TOKEN_EQUALS
	beq t0, t1, .Lbuild_binary_expression_equal

	li t1, TOKEN_ASTERISK
	beq t0, t1, .Lbuild_binary_expression_product

	li t1, TOKEN_MINUS
	beq t0, t1, .Lbuild_binary_expression_minus

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_equal:
	mv s1, a0 # Skip =.
	li a0, 1
	call _build_expression
	la a0, asm_sub_a0_a1
	li a1, ASM_SUB_A0_A1_SIZE
	call _write_out

	la a0, asm_seqz_a0
	li a1, ASM_SEQZ_A0_SIZE
	call _write_out

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_and:
	mv s1, a0 # Skip &.
	li a0, 1
	call _build_expression
	la a0, asm_and_a0_a1
	li a1, ASM_AND_A0_A1_SIZE
	call _write_out

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_or:
	mv s1, a0 # Skip or.
	li a0, 1
	call _build_expression
	la a0, asm_or_a0_a1
	li a1, ASM_OR_A0_A1_SIZE
	call _write_out

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_plus:
	mv s1, a0 # Skip +.
	li a0, 1
	call _build_expression
	la a0, asm_add_a0_a1
	li a1, ASM_ADD_A0_A1_SIZE
	call _write_out

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_minus:
	mv s1, a0 # Skip -.
	li a0, 1
	call _build_expression
	la a0, asm_sub_a0_a1
	li a1, ASM_SUB_A0_A1_SIZE
	call _write_out

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_product:
	mv s1, a0 # Skip *.
	li a0, 1
	call _build_expression
	la a0, asm_mul_a0_a1
	li a1, ASM_MUL_A0_A1_SIZE
	call _write_out

	j .Lbuild_binary_expression_end

.Lbuild_binary_expression_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Checks whether the given identifier starts with "loca".
# Parameters:
# a0 - Pointer to the identifier.
# a1 - Identifier length.
#
# Sets a0 to 1 if the identifier starts with "loca", otherwise to 0.
.type _is_local_identifier, @function
_is_local_identifier:
	# Prologue.
	addi sp, sp, -16
	sw ra, 12(sp)
	sw s0, 8(sp)
	addi s0, sp, 16

	li t0, 0x61636f6c # loca
	sw t0, 4(sp)
	# a0 is already set.
	addi a1, sp, 4
	li a2, 4
	call _memcmp
	seqz a0, a0

	# Epilogue.
	lw ra, 12(sp)
	lw s0, 8(sp)
	addi sp, sp, 16
	ret

# Checks whether the given identifier is a saved register name, like s1 or s2.
# Parameters:
# a0 - Pointer to the identifier.
# a1 - Identifier length.
#
# Sets a0 to 1 if the identifier is a preserved register, otherwise to 0.
.type _is_register_identifier, @function
_is_register_identifier:
	# Prologue.
	addi sp, sp, -8
	sw ra, 4(sp)
	sw s0, 0(sp)
	addi s0, sp, 8

	lbu a0, (a0)
	addi a1, a1, -2
	seqz a1, a1
	addi t0, a0, -'s'
	seqz t0, t0
	and a0, a1, t0

	# Epilogue.
	lw ra, 4(sp)
	lw s0, 0(sp)
	addi sp, sp, 8
	ret

# Parameters:
# a0 - Identifier length.
# a1 - Register number as character.
.type _compile_identifier_expression, @function
_compile_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.

	mv a0, s1
	lw a1, 20(sp)
	call _is_local_identifier
	bnez a0, .Lcompile_identifier_expression_local

	mv a0, s1
	lw a1, 20(sp)
	call _is_register_identifier
	bnez a0, .Lcompile_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, .Lcompile_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 .Lcompile_identifier_expression_end

.Lcompile_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 .Lcompile_identifier_expression_end

.Lcompile_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 .Lcompile_identifier_expression_end

.Lcompile_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.
.type _build_expression, @function
_build_expression:
	# Prologue.
	addi sp, sp, -48
	sw ra, 44(sp)
	sw s0, 40(sp)
	addi s0, sp, 48

	addi a0, a0, '0' # Make the register number to a character.
	sw a0, 36(sp) # And save it.

	mv a0, s1
	addi a1, sp, 24
	call _tokenize_next
	sw a0, 20(sp)

	lw a0, 24(sp)

	li t0, TOKEN_MINUS
	beq a0, t0, .Lbuild_expression_negate

	li t0, TOKEN_AT
	beq a0, t0, .Lbuild_expression_address

	li t0, TOKEN_INTEGER
	beq a0, t0, .Lbuild_expression_literal

	lw a0, 32(sp)
	lbu a0, (a0)
	li t0, '_'
	beq a0, t0, .Lbuild_expression_call

	lw s1, 32(sp)
	lw a0, 28(sp)
	lw a1, 36(sp)
	call _compile_identifier_expression

	j .Lbuild_expression_advance

.Lbuild_expression_negate:
	lw s1, 20(sp) # Skip the -.
	mv a0, zero
	call _build_expression

	la a0, asm_neg_a0
	li a1, ASM_NEG_A0_SIZE
	call _write_out

	j .Lbuild_expression_end

.Lbuild_expression_address:
	lw t1, 36(sp)
	li t0, 0x20 # _
	sw t0, 16(sp)
	li t0, 0x2c707320 # _sp,
	sw t0, 12(sp)
	li t0, 0x2c006120 # _a\0,
	sw t0, 8(sp)
	sb t1, 10(sp)
	li t0, 0x69646461 # addi
	sw t0, 4(sp)
	addi a0, sp, 4
	li a1, 13
	call _write_out

	lw a0, 20(sp) # Skip @.
	addi a1, sp, 24
	call _tokenize_next
	mv s1, a0

	lw a0, 32(sp)
	lw a1, 28(sp)
	addi a0, a0, 4 # Skip the "loca" variable prefix.
	addi a1, a1, -4 # Skip the "loca" variable prefix.
	call _write_out

	li a0, '\n'
	call _put_char

	j .Lbuild_expression_end

.Lbuild_expression_call:
	lw a0, 20(sp)
	addi a1, sp, 8
	call _tokenize_next
	mv s1, a0

	lw a0, 32(sp)
	lw a1, 28(sp)
	call _compile_call

	j .Lbuild_expression_end

.Lbuild_expression_literal:
	lw t1, 36(sp)
	li t0, 0x00202c00 # \0,_
	or t0, t0, t1
	sw t0, 16(sp)
	li t0, 0x6120696c # li a
	sw t0, 12(sp)
	addi a0, sp, 12
	li a1, 7
	call _write_out

	lw a0, 32(sp)
	lw a1, 28(sp)
	call _write_out

	li a0, '\n'
	call _put_char

	j .Lbuild_expression_advance

.Lbuild_expression_advance:
	lw s1, 20(sp)

.Lbuild_expression_end:
	# Epilogue.
	lw ra, 44(sp)
	lw s0, 40(sp)
	addi sp, sp, 48
	ret

# Compiles an lvalue.
#
# Parameters:
# a0 - Pointer to the identifier.
# a1 - Identifier length.
.type _compile_designator_expression, @function
_compile_designator_expression:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	sw a0, 20(sp) # Identifier pointer.
	sw a1, 16(sp) # Identifier length.

	lw a0, 20(sp)
	lw a1, 16(sp)
	call _is_local_identifier
	bnez a0, .Lcompile_designator_expression_local

	lw a0, 20(sp)
	lw a1, 16(sp)
	call _is_register_identifier
	bnez a0, .Lcompile_designator_expression_saved

.Lcompile_designator_expression_local:
	li t0, 0x202c30 # 0,_
	sw t0, 12(sp)
	li t0, 0x61207773 # sw a
	sw t0, 8(sp)
	addi a0, sp, 8
	li a1, 7
	call _write_out

	lw a0, 20(sp)
	lw a1, 16(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, 12(sp)
	li t0, 0x29707328 # (sp)
	sw t0, 8(sp)
	addi a0, sp, 8
	li a1, 5
	call _write_out

	j .Lcompile_designator_expression_end

.Lcompile_designator_expression_saved:
	li t0, 0x20766d # mv_
	sw t0, 12(sp)
	addi a0, sp, 12
	li a1, 3
	call _write_out

	lw a0, 20(sp)
	lw a1, 16(sp)
	call _write_out

	li t0, 0x0a # \n
	sw t0, 12(sp)
	li t0, 0x3061202c # , a0
	sw t0, 8(sp)
	addi a0, sp, 8
	li a1, 5
	call _write_out

	j .Lcompile_designator_expression_end

.Lcompile_designator_expression_end:

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Compiles a statement beginning with an identifier.
#
# Left values should be variables named "loca n", where n is the offset
# of the variable on the stack, like loca8 or loca4.
.type _compile_identifier, @function
_compile_identifier:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	# Save the pointer to the identifier and its length on the stack.
	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next
	addi a1, sp, 0
	call _tokenize_next
	mv s1, a0

	lw t0, 0(sp)

	li t1, TOKEN_ASSIGN
	beq t0, t1, .Lcompile_identifier_assign

	li t1, TOKEN_LEFT_PAREN
	beq t0, t1, .Lcompile_identifier_call

	j .Lcompile_identifier_end

.Lcompile_identifier_call:
	lw a0, 20(sp)
	lw a1, 16(sp)
	call _compile_call

	j .Lcompile_identifier_end

.Lcompile_identifier_assign:
	call _build_binary_expression
	lw a0, 20(sp)
	lw a1, 16(sp)
	call _compile_designator_expression

	j .Lcompile_identifier_end

.Lcompile_identifier_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Compiles a procedure call. Expects s1 to point to the first argument.
# a0 - Pointer to the procedure name.
# a1 - Length of the procedure name.
#
# Returns the procedure result in a0.
.type _compile_call, @function
_compile_call:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	sw a0, 20(sp)
	sw a1, 16(sp)
	sw zero, 12(sp) # Argument count for a procedure call.

.Lcompile_call_paren:
	lbu t0, (s1)
	li t1, 0x29 # )
	beq t0, t1, .Lcompile_call_complete

.Lcompile_call_argument:
	li a0, 0
	call _build_expression

	li t0, 0x202c30 # 0,_
	sw t0, 8(sp)
	li t0, 0x61207773 # sw a
	sw t0, 4(sp)
	addi a0, sp, 4
	li a1, 7
	call _write_out

	lw t0, 12(sp) # Argument count for a procedure call.

	# Only 6 arguments are supported with a0-a5.
	# Save all arguments on the stack so they aren't overriden afterwards.
	li a0, -4
	mul a0, t0, a0
	addi a0, a0, 60
	call _printi

	li t0, '\n'
	sw t0, 8(sp)
	li t0, 0x29707328 # (sp)
	sw t0, 4(sp)
	addi a0, sp, 4
	li a1, 5
	call _write_out

	lbu t0, (s1)
	li t1, ','
	bne t0, t1, .Lcompile_call_paren

	lw t0, 12(sp) # Argument count for a procedure call.
	addi t0, t0, 1
	sw t0, 12(sp)

	addi s1, s1, 1 # Skip the comma between the arguments.
	j .Lcompile_call_argument

.Lcompile_call_complete:
	sw zero, 12(sp)

.Lcompile_call_restore:
	# Just go through all a0-a5 registers and read them from stack.
	# If this stack value contains garbage, the procedure just shouldn't use it.
	la a0, asm_restore_parameters
	li a1, ASM_RESTORE_PARAMETERS_SIZE
	call _write_out

.Lcompile_call_perform:
	li t0, 0x20
	sw t0, 8(sp)
	li t0, 0x6c6c6163 # call
	sw t0, 4(sp)
	addi a0, sp, 4
	li a1, 5
	call _write_out

	lw a0, 20(sp)
	lw a1, 16(sp)
	call _write_out

	li a0, '\n'
	call _put_char

	addi s1, s1, 1 # Skip the close paren.

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Walks through the procedure definitions.
.type _compile_procedure_section, @function
_compile_procedure_section:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

.Lcompile_procedure_section_loop:
	mv a0, s1
	addi a1, sp, 4
	call _tokenize_next
	li t0, TOKEN_PROC
	lw t1, 4(sp)
	bne t0, t1, .Lcompile_procedure_section_end

	call _compile_procedure

	j .Lcompile_procedure_section_loop

.Lcompile_procedure_section_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

.type _compile_module_declaration, @function
_compile_module_declaration:
	# Prologue.
	addi sp, sp, -24
	sw ra, 20(sp)
	sw s0, 16(sp)
	addi s0, sp, 24

	la a0, global_start
	li a1, GLOBAL_START_SIZE
	call _write_out

	# Skip "program".
	mv a0, s1
	addi a1, sp, 4
	call _tokenize_next
	mv s1, a0

	# Epilogue.
	lw ra, 20(sp)
	lw s0, 16(sp)
	addi sp, sp, 24
	ret

.type _compile_constant_section, @function
_compile_constant_section:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 4
	call _tokenize_next
	li t0, TOKEN_CONST
	lw t1, 4(sp)
	bne t0, t1, .Lcompile_constant_section_end
	mv s1, a0

	la a0, section_rodata
	li a1, SECTION_RODATA_SIZE
	call _write_out

.Lcompile_constant_section_item:
	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next

	lw t0, 12(sp)
	li t1, TOKEN_IDENTIFIER

	bne t0, t1, .Lcompile_constant_section_end
	lw s1, 20(sp)

	call _compile_constant
	j .Lcompile_constant_section_item

.Lcompile_constant_section_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

.type _compile_constant, @function
_compile_constant:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next
	addi a1, sp, 0
	call _tokenize_next # Skip the assignment sign.
	mv s1, a0
	# Write identifier the identifier.
	lw a0, 20(sp)
	lw a1, 16(sp)
	call _write_out

	# : .long
	li t0, 0x20676e6f # ong_
	sw t0, 4(sp)
	li t0, 0x6c2e203a # : .l
	sw t0, 0(sp)
	mv a0, sp
	li a1, 8
	call _write_out

	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next
	mv s1, a0

	lw a0, 20(sp) # Save the literal pointer before advancing it.
	lw a1, 16(sp) # The literal length.
	call _write_out

	li a0, '\n'
	call _put_char

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

.type _compile_variable_section, @function
_compile_variable_section:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 4
	call _tokenize_next
	li t0, TOKEN_VAR
	lw t1, 4(sp)
	bne t0, t1, .Lcompile_variable_section_end
	mv s1, a0

	la a0, section_bss
	li a1, SECTION_BSS_SIZE
	call _write_out

.Lcompile_variable_section_item:
	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next
	lw t0, 12(sp)
	li t1, TOKEN_IDENTIFIER

	bne t0, t1, .Lcompile_variable_section_end
	lw s1, 20(sp) # Advance to the beginning of the variable name.

	call _compile_variable
	j .Lcompile_variable_section_item

.Lcompile_variable_section_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Compile a global variable.
.type _compile_variable, @function
_compile_variable:
	# Prologue.
	addi sp, sp, -48
	sw ra, 44(sp)
	sw s0, 40(sp)
	addi s0, sp, 48

	# Save the identifier on the stack since it should emitted multiple times.
	mv a0, s1
	addi a1, sp, 28
	call _tokenize_next
	addi a1, sp, 4
	call _tokenize_next # Skip the colon in front of the type.
	addi a1, sp, 4
	call _tokenize_next # Skip the opening bracket.
	addi a1, sp, 16
	call _tokenize_next # Save the array size on the stack since it has to be emitted multiple times.
	addi a1, sp, 4
	call _tokenize_next # Skip the closing bracket.
	addi a1, sp, 4
	call _tokenize_next # Skip the type.
	mv s1, a0

	# .type identifier, @object
	la a0, asm_type
	li a1, ASM_TYPE_SIZE
	call _write_out

	lw a0, 36(sp)
	lw a1, 32(sp)
	call _write_out

	la a0, asm_type_object
	li a1, ASM_TYPE_OBJECT_SIZE
	call _write_out

	# identifier: .zero size
	lw a0, 36(sp)
	lw a1, 32(sp)
	call _write_out

	li t0, 0x206f7265 # ero_
	sw t0, 12(sp)
	li t0, 0x7a2e203a # : .z
	sw t0, 8(sp)
	addi a0, sp, 8
	li a1, 8
	call _write_out

	lw a0, 24(sp)
	lw a1, 20(sp)
	call _write_out

	li a0, '\n'
	call _put_char

	# Epilogue.
	lw ra, 44(sp)
	lw s0, 40(sp)
	addi sp, sp, 48
	ret

.type _compile_procedure, @function
_compile_procedure:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next	# Skip proc.
	addi a1, sp, 12
	call _tokenize_next
	mv s1, a0

	lw a0, 16(sp)
	lw a1, 20(sp)
	call _write_procedure_head

	# Skip all declarations until we find the "begin" keyword, denoting the
	# beginning of the procedure body.
.Lcompile_procedure_begin:
	mv a0, s1
	addi a1, sp, 4
	call _tokenize_next
	mv s1, a0
	lw t0, 4(sp)
	li t1, TOKEN_BEGIN
	bne t0, t1, .Lcompile_procedure_begin

	# Generate the procedure prologue with a predefined stack size.
	la a0, prologue
	li a1, PROLOGUE_SIZE
	call _write_out

	# Save passed arguments on the stack.
	la a0, asm_preserve_parameters
	li a1, ASM_PRESERVE_PARAMETERS_SIZE
	call _write_out

	# Generate the body of the procedure.
	call _compile_statements
	mv s1, a0 # Skip end.

	/* DEBUG
	sw a0, 8(sp)
	lw a1, 12(sp)
	li a2, TOKEN_END
	sub a1, a1, a2
	seqz a1, a1
	seqz a0, a0
	addi a0, a0, '0'
	addi a1, a1, '0'
	sb a0, 4(sp)
	sb a1, 5(sp)
	addi a0, sp, 4
	li a1, 2
	call _write_error
	lw a0, 8(sp) */

	# Generate the procedure epilogue with a predefined stack size.
	la a0, epilogue
	li a1, EPILOGUE_SIZE
	call _write_out

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Compiles a goto statement to an uncoditional jump.
.type _compile_goto, @function
_compile_goto:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next # Skip the goto keyword.
	addi a1, sp, 0
	call _tokenize_next # We should be on dot the label is beginning with.
	addi a1, sp, 0
	call _tokenize_next# Save the label name.
	mv s1, a0

	li t0, 0x2e206a # j .
	sw t0, 12(sp)
	addi a0, sp, 12
	li a1, 3
	call _write_out

	lw a0, 8(sp) # Saved dot position.
	lw a1, 4(sp)
	call _write_out

	li a0, '\n'
	call _put_char

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Rewrites a label to assembly.
.type _compile_label, @function
_compile_label:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 8
	call _tokenize_next # Dot starting the label.
	addi a1, sp, 8
	call _tokenize_next
	mv s1, a0

	li a0, '.'
	call _put_char
	lw a0, 16(sp)
	lw a1, 12(sp)
	call _write_out
	li a0, ':'
	call _put_char
	li a0, '\n'
	call _put_char

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Just skips the return keyword and evaluates the return expression.
.type _compile_return, @function
_compile_return:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 12
	call _tokenize_next
	mv s1, a0 # Skip return.

	call _build_binary_expression

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

.type _compile_if, @function
_compile_if:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next
	mv s1, a0 # Skip the if.

	call _build_binary_expression

	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next
	mv s1, a0 # Skip the then.

	# Label prefix.
	li t0, 0x66694c2e # .Lif
	sw t0, 20(sp)

	li t0, 0x202c3061 # a0,_
	sw t0, 16(sp)
	li t0, 0x207a7165 # eqz_
	sw t0, 12(sp)
	li t0, 0x62626262 # bbbb
	sb t0, 11(sp)

	addi a0, sp, 11
	li a1, 13
	call _write_out

	# Write the label counter.
	mv a0, s2
	call _printi

	li a0, '\n'
	call _put_char

	call _compile_statements
	mv s1, a0 # Skip end.

	# Write the label prefix.
	addi a0, sp, 20
	li a1, 4
	call _write_out

	# Write the label counter.
	mv a0, s2
	call _printi

	# Finalize the label.
	li t0, 0x0a3a # :\n
	sh t0, 16(sp)
	addi a0, sp, 16
	li a1, 2
	call _write_out

	addi s2, s2, 1 # Increment the label counter.

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Writes:
# .type identifier, @function
# identifier:
#
# Parameters:
# a0 - Identifier length.
# a0 - Identifier pointer.
.type _write_procedure_head, @function
_write_procedure_head:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	sw a0, 16(sp)
	sw a1, 20(sp)

	# .type identifier, @function
	la a0, asm_type
	li a1, ASM_TYPE_SIZE
	call _write_out

	lw a0, 20(sp)
	lw a1, 16(sp)
	call _write_out

	la a0, asm_type_function
	li a1, ASM_TYPE_FUNCTION_SIZE
	call _write_out

	lw a0, 20(sp)
	lw a1, 16(sp)
	call _write_out

	li t0, 0x0a3a # :\n
	sw t0, 12(sp)
	addi a0, sp, 12
	li a1, 2
	call _write_out

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Compiles a list of statements delimited by semicolons.
#
# Sets a0 to the end of the token finishing the list
# (should be the "end" token in a valid program).
.type _compile_statements, @function
_compile_statements:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	# Generate the body of the procedure.
	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next
	lw t0, 0(sp)
	li t1, TOKEN_END

	beq t0, t1, .Lcompile_statements_end

.Lcompile_statements_body:
	call _compile_statement

	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next
	lw t0, 0(sp)
	li t1, TOKEN_SEMICOLON

	bne t0, t1, .Lcompile_statements_end
	mv s1, a0

	j .Lcompile_statements_body

.Lcompile_statements_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Checks for the type of the current statement and compiles it.
.type _compile_statement, @function
_compile_statement:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	mv a0, s1
	addi a1, sp, 0
	call _tokenize_next
	lw t0, 0(sp)

	li t1, TOKEN_IDENTIFIER
	beq t0, t1, .Lcompile_statement_identifier

	li t1, TOKEN_GOTO
	beq t0, t1, .Lcompile_statement_goto

	li t1, TOKEN_RETURN
	beq t0, t1, .Lcompile_statement_return

	li t1, TOKEN_IF
	beq t0, t1, .Lcompile_statement_if

	li t1, TOKEN_DOT
	beq t0, t1, .Lcompile_statement_label

	unimp # Else.

.Lcompile_statement_if:
	call _compile_if
	j .Lcompile_statement_end

.Lcompile_statement_label:
	call _compile_label
	j .Lcompile_statement_end

.Lcompile_statement_return:
	call _compile_return
	j .Lcompile_statement_end

.Lcompile_statement_goto:
	call _compile_goto
	j .Lcompile_statement_end

.Lcompile_statement_identifier:
	call _compile_identifier
	j .Lcompile_statement_end

.Lcompile_statement_end:
	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

# Prints ".section .text" and exits.
.type _compile_text_section, @function
_compile_text_section:
	# Prologue.
	addi sp, sp, -16
	sw ra, 12(sp)
	sw s0, 8(sp)
	addi s0, sp, 16

	la a0, section_text
	li a1, SECTION_TEXT_SIZE
	call _write_out

	# Epilogue.
	lw ra, 12(sp)
	lw s0, 8(sp)
	addi sp, sp, 16
	ret

.type _compile_entry_point, @function
_compile_entry_point:
	# Prologue.
	addi sp, sp, -32
	sw ra, 28(sp)
	sw s0, 24(sp)
	addi s0, sp, 32

	# .type _start, @function
	la a0, asm_start
	li a1, ASM_START_SIZE
	call _write_out

	mv a0, s1
	addi a1, sp, 4
	call _tokenize_next
	mv s1, a0 # Skip begin.

	# Generate the body of the procedure.
	call _compile_statements
	mv s1, a0 # Skip end.

	la a0, asm_exit
	li a1, ASM_EXIT_SIZE
	call _write_out

	# Epilogue.
	lw ra, 28(sp)
	lw s0, 24(sp)
	addi sp, sp, 32
	ret

.type _compile, @function
_compile:
	# Prologue.
	addi sp, sp, -16
	sw ra, 12(sp)
	sw s0, 8(sp)
	addi s0, sp, 16

	call _compile_module_declaration
	call _compile_import
	call _compile_constant_section
	call _compile_variable_section
	call _compile_text_section
	call _compile_procedure_section
	call _compile_entry_point

	# Epilogue.
	lw ra, 12(sp)
	lw s0, 8(sp)
	addi sp, sp, 16
	ret

# Entry point.
.type _start, @function
_start:
	# Read the source from the standard input.
	la a0, source_code
	li a1, SOURCE_BUFFER_SIZE # Buffer size.
	call _read_file

	li s2, 1
	call symbol_table_build
	call _compile

	# Call exit.
	li a0, 0   # Use 0 return code.
	call _exit