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elna/boot/stage6.elna

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# 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/.
# Stage4 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)
_write_s(source_code_position, v0);
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
_write_z(@asm_li);
_write_z(@asm_t0);
_write_z(@asm_comma);
_read_token();
_write_token();
_advance_token();
_write_c('\n');
end;
proc _compile_character_literal();
begin
_write_z(@asm_li);
_write_z(@asm_t0);
_write_z(@asm_comma);
_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();
_write_z(@asm_lw);
_write_z(@asm_t0);
_write_z(@asm_comma);
_write_c('(');
_write_z(@asm_t0);
_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)
v4 := source_code_position
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.
_write_z(@asm_sw);
_write_z(@asm_t0);
_write_z(@asm_comma);
# 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('(');
_write_z(@asm_sp);
_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)
_write_z(@asm_lw);
_write_c('a');
lw a0, 8(sp)
_write_i();
_write_z(@asm_comma);
# 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('(');
_write_z(@asm_sp);
_write_c(')');
_write_c('\n');
goto .compile_call_finalize;
.compile_call_end:
_write_z(@asm_call);
_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)
_write_z(@asm_j);
_write_token(v0);
_advance_token();
end;
proc _compile_local_designator();
begin
# Skip "v" in the local variable name.
_advance_token(1);
_write_z(@asm_addi);
_write_z(@asm_t0);
_write_z(@asm_comma);
_write_z(@asm_sp);
_write_z(@asm_comma);
# Read local variable stack offset and save it.
v0 := source_code_position;
_read_token();
sw a0, 4(sp)
_write_token();
_advance_token();
_write_c('\n');
end;
proc _compile_global_designator();
begin
_write_z(@asm_la);
_write_z(@asm_t0);
_write_z(@asm_comma);
_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.
_write_z(@asm_sw);
_write_z(@asm_t0);
_write_z(@asm_comma);
_write_i(20);
_write_c('(');
_write_z(@asm_sp);
_write_c(')');
_write_c('\n');
# Skip the assignment sign (:=) with surrounding whitespaces.
_advance_token(4);
# Compile the assignment.
_compile_expression();
_write_z(@asm_lw);
_write_z(@asm_t1);
_write_z(@asm_comma);
_write_i(20);
_write_c('(');
_write_z(@asm_sp);
_write_c(')');
_write_c('\n');
_write_z(@asm_sw);
_write_z(@asm_t0);
_write_z(@asm_comma);
_write_c('(');
_write_z(@asm_t1);
_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);
_write_z(@asm_colon);
# Skip the function name and trailing parens, semicolon, "begin" and newline.
lw a0, 0(sp)
addi a0, a0, 10
_advance_token();
_write_z(@asm_prologue);
_compile_procedure_body();
# Write the epilogue.
_write_z(@asm_epilogue);
# 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
# 8 is ".section" length.
_memcmp(source_code_position, @keyword_section, 8);
beqz a0, .compile_section
# 5 is ".type" length.
_memcmp(source_code_position, @keyword_type, 5);
beqz a0, .compile_type
# 5 is "proc " length. Space is needed to distinguish from "procedure".
_memcmp(source_code_position, @keyword_proc, 5);
beqz a0, .compile_procedure
# 6 is ".globl" length.
_memcmp(source_code_position, @keyword_global, 6);
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.
# Second argument is buffer size. Modifying update the source_code definition.
_read_file(@source_code, 81920);
_compile();
_exit(0);
end;