From 48882522746873d48b563ec66321ef99a51badbc Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Thu, 4 Sep 2025 22:07:01 +0200
Subject: [PATCH] Implement string literals

---
 boot/stage5.elna |  52 ++++++++++--
 boot/stage6.elna | 212 ++++++++++++++++++++---------------------------
 2 files changed, 132 insertions(+), 132 deletions(-)

diff --git a/boot/stage5.elna b/boot/stage5.elna
index 3aed6c3..88b407f 100644
--- a/boot/stage5.elna
+++ b/boot/stage5.elna
@@ -2,7 +2,7 @@
 # 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.
+# Stage5 compiler.
 #
 # - Stack size increased to 128 bytes per procedure.
 #   7 words on the stack, 92 - 120, are reversed for procedure arguments (caller side).
@@ -13,6 +13,7 @@
 # - Binary addition "+" and multiplication "*".
 # - Binary logical operations: & (and), or and xor.
 # - Binary comparison operations: =, <, <=, >, >=, <>.
+# - Return statement.
 
 .section .rodata
 
@@ -23,7 +24,7 @@ keyword_section: .ascii ".section"
 keyword_type: .ascii ".type"
 
 .type keyword_ret, @object
-keyword_ret: .ascii "ret"
+keyword_ret: .ascii "\tret"
 
 .type keyword_global, @object
 keyword_global: .ascii ".globl"
@@ -97,6 +98,9 @@ asm_or: .string "\tor "
 .type asm_xor, @object
 asm_xor: .string "\txor "
 
+.type asm_xori, @object
+asm_xori: .string "\txori "
+
 .type asm_sub, @object
 asm_sub: .string "\tsub "
 
@@ -109,6 +113,9 @@ asm_snez: .string "\tsnez "
 .type asm_slt, @object
 asm_slt: .string "\tslt "
 
+.type asm_mv, @object
+asm_mv: .string "\tmv "
+
 .type asm_comma, @object
 asm_comma: .string ", "
 
@@ -889,16 +896,18 @@ begin
 	_write_z(@asm_slt);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
-	_write_register('t', 1);
-	_write_z(@asm_comma);
 	_write_register('t', 0);
+	_write_z(@asm_comma);
+	_write_register('t', 1);
 	_write_c('\n');
 
 	# Execute the operation.
-	_write_z(@asm_not);
+	_write_z(@asm_xori);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
 	_write_register('t', 0);
+	_write_z(@asm_comma);
+	_write_i(1);
 	_write_c('\n');
 
 	goto .compile_expression_end;
@@ -933,16 +942,18 @@ begin
 	_write_z(@asm_slt);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
-	_write_register('t', 0);
-	_write_z(@asm_comma);
 	_write_register('t', 1);
+	_write_z(@asm_comma);
+	_write_register('t', 0);
 	_write_c('\n');
 
 	# Execute the operation.
-	_write_z(@asm_not);
+	_write_z(@asm_xori);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
 	_write_register('t', 0);
+	_write_z(@asm_comma);
+	_write_i(1);
 	_write_c('\n');
 
 	goto .compile_expression_end;
@@ -1167,6 +1178,19 @@ begin
 	_write_c(')');
 end;
 
+proc _compile_return_statement();
+begin
+	# Skip "return" keyword and whitespace after it.
+	_advance_token(7);
+	_compile_expression();
+
+	_write_z(@asm_mv);
+	_write_register('a', 0);
+	_write_z(@asm_comma);
+	_write_register('t', 0);
+
+end;
+
 proc _compile_statement();
 begin
 	# This is a call if the statement starts with an underscore.
@@ -1185,6 +1209,10 @@ begin
 	li t1, 'v'
 	beq t0, t1, .compile_statement_assignment
 
+	# keyword_ret contains "\tret", so it's 4 bytes long.
+	_memcmp(source_code_position, @keyword_ret, 4);
+	beqz a0, .compile_statement_return
+
 	_compile_line();
 	goto .compile_statement_end;
 
@@ -1206,9 +1234,15 @@ begin
 
 	goto .compile_statement_semicolon;
 
+.compile_statement_return:
+	_advance_token(1);
+	_compile_return_statement();
+	_write_c('\n');
+
+	goto .compile_statement_end;
+
 .compile_statement_semicolon:
 	_advance_token(2);
-
 	_write_c('\n');
 
 .compile_statement_end:
diff --git a/boot/stage6.elna b/boot/stage6.elna
index 3aed6c3..f412cc6 100644
--- a/boot/stage6.elna
+++ b/boot/stage6.elna
@@ -1,18 +1,9 @@
-# This Source Code Form is subject to the terms of the Mozilla Public License,
+# ihis 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.
+# Stage6 compiler.
 #
-# - Stack size increased to 128 bytes per procedure.
-#   7 words on the stack, 92 - 120, are reversed for procedure arguments (caller side).
-#   7 words on the stack, 64 - 92, are reserved for procedure parameters (callee side).
-#   The first parameter is in 88, the second in 84 and so forth.
-# - Unary negate operation, e.g. -5.
-# - Unary locical not operation "~".
-# - Binary addition "+" and multiplication "*".
-# - Binary logical operations: & (and), or and xor.
-# - Binary comparison operations: =, <, <=, >, >=, <>.
 
 .section .rodata
 
@@ -23,7 +14,7 @@ keyword_section: .ascii ".section"
 keyword_type: .ascii ".type"
 
 .type keyword_ret, @object
-keyword_ret: .ascii "ret"
+keyword_ret: .ascii "\tret"
 
 .type keyword_global, @object
 keyword_global: .ascii ".globl"
@@ -97,6 +88,9 @@ asm_or: .string "\tor "
 .type asm_xor, @object
 asm_xor: .string "\txor "
 
+.type asm_xori, @object
+asm_xori: .string "\txori "
+
 .type asm_sub, @object
 asm_sub: .string "\tsub "
 
@@ -109,6 +103,9 @@ asm_snez: .string "\tsnez "
 .type asm_slt, @object
 asm_slt: .string "\tslt "
 
+.type asm_mv, @object
+asm_mv: .string "\tmv "
+
 .type asm_comma, @object
 asm_comma: .string ", "
 
@@ -202,7 +199,7 @@ begin
 
 	_memcpy();
 
-	lw a0, 0(sp)
+	return v0
 end;
 
 # Writes a number to the standard output.
@@ -211,8 +208,7 @@ end;
 # a0 - Whole number.
 proc _write_i();
 begin
-	addi a1, sp, 0
-	_print_i();
+	_print_i(v88, @v0);
 
 	mv a1, a0
 	addi a0, sp, 0
@@ -223,10 +219,7 @@ 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();
+	_write_s(@v88, 1);
 end;
 
 # Write null terminated string.
@@ -235,22 +228,17 @@ end;
 # a0 - String.
 proc _write_z();
 begin
-	sw a0, 0(sp)
-
 .write_z_loop:
 	# Check for 0 character.
+	lw a0, 88(sp)
 	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)
+	v88 := v88 + 1;
 
 	goto .write_z_loop;
 
@@ -260,21 +248,21 @@ 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'
+	v0 := v88 >= 'A';
+	v4 := v88 <= 'Z';
+
+	return v0 & v4
 
-	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'
+	v0 := v88 >= 'a';
+	v4 := v88 <= 'z';
+
+	return v0 & v4
 
-	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.
@@ -310,12 +298,10 @@ end;
 # 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'
+	v0 := v88 >= '0';
+	v4 := v88 <= '9';
 
-	sltiu t2, a0, '9' + 1 # t2 = a0 <= '9'
-
-	and a0, t1, t2
+	return v0 & v4
 end;
 
 proc _is_alnum();
@@ -336,12 +322,13 @@ end;
 # 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.
+	# Current token position.
+	v0 := source_code_position;
+	# Token length.
+	v4 := 0;
 
 .read_token_loop:
+	lw t0, 0(sp)
 	lb t0, (t0) # Current character.
 
 	# First we try to read a derictive.
@@ -358,18 +345,13 @@ begin
 
 .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)
+	v4 := v4 + 1;
+	v0 := v0 + 1;
 
 	goto .read_token_loop;
 
 .read_token_end:
-	lw a0, 4(sp)
+	return v4
 end;
 
 # a0 - First pointer.
@@ -445,9 +427,8 @@ end;
 # Returns a0 unchanged.
 proc _write_token();
 begin
-	sw a0, 0(sp)
-	_write_s(source_code_position, v0);
-	lw a0, 0(sp)
+	_write_s(source_code_position, v88);
+	return v88
 end;
 
 proc _compile_section();
@@ -889,16 +870,18 @@ begin
 	_write_z(@asm_slt);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
-	_write_register('t', 1);
-	_write_z(@asm_comma);
 	_write_register('t', 0);
+	_write_z(@asm_comma);
+	_write_register('t', 1);
 	_write_c('\n');
 
 	# Execute the operation.
-	_write_z(@asm_not);
+	_write_z(@asm_xori);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
 	_write_register('t', 0);
+	_write_z(@asm_comma);
+	_write_i(1);
 	_write_c('\n');
 
 	goto .compile_expression_end;
@@ -933,16 +916,18 @@ begin
 	_write_z(@asm_slt);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
-	_write_register('t', 0);
-	_write_z(@asm_comma);
 	_write_register('t', 1);
+	_write_z(@asm_comma);
+	_write_register('t', 0);
 	_write_c('\n');
 
 	# Execute the operation.
-	_write_z(@asm_not);
+	_write_z(@asm_xori);
 	_write_register('t', 0);
 	_write_z(@asm_comma);
 	_write_register('t', 0);
+	_write_z(@asm_comma);
+	_write_i(1);
 	_write_c('\n');
 
 	goto .compile_expression_end;
@@ -960,12 +945,10 @@ begin
 	_read_token();
 	sw a0, 0(sp)
 	v4 := source_code_position;
-
-	sw zero, 8(sp)
+	v8 := 0;
 
 	# Skip the identifier and left paren.
-	addi a0, a0, 1
-	_advance_token();
+	_advance_token(v0 + 1);
 
 	la t0, source_code_position
 	lw t0, (t0)
@@ -983,12 +966,9 @@ begin
 	_write_z(@asm_comma);
 
 	# Calculate the stack offset: 116 - (4 * argument_counter)
-	lw t0, 8(sp)
-	li t1, 4
-	mul t0, t0, t1
-	li t1, 116
-	sub a0, t1, t0
-	_write_i();
+	v12 := v8 * 4;
+	v12 := 116 + -v12;
+	_write_i(v12);
 
 	_write_c('(');
 	_write_z(@asm_sp);
@@ -997,9 +977,7 @@ begin
 	_write_c('\n');
 
 	# Add one to the argument counter.
-	lw t0, 8(sp)
-	addi t0, t0, 1
-	sw t0, 8(sp)
+	v8 := v8 + 1;
 
 	la t0, source_code_position
 	lw t0, (t0)
@@ -1018,25 +996,19 @@ begin
 	beqz t0, .compile_call_end
 
 	# Decrement the argument counter.
-	lw t0, 8(sp)
-	addi t0, t0, -1
-	sw t0, 8(sp)
+	v8 := v8 + -1;
 
 	_write_z(@asm_lw);
 
 	_write_c('a');
-	lw a0, 8(sp)
-	_write_i();
+	_write_i(v8);
 
 	_write_z(@asm_comma);
 
 	# Calculate the stack offset: 116 - (4 * argument_counter)
-	lw t0, 8(sp)
-	li t1, 4
-	mul t0, t0, t1
-	li t1, 116
-	sub a0, t1, t0
-	_write_i();
+	v12 := v8 * 4;
+	v12 := 116 + -v12;
+	_write_i(v12);
 
 	_write_c('(');
 	_write_z(@asm_sp);
@@ -1048,7 +1020,6 @@ begin
 
 .compile_call_end:
 	_write_z(@asm_call);
-
 	_write_s(v4, v0);
 
 	# Skip the right paren.
@@ -1080,14 +1051,9 @@ begin
 	_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;
@@ -1103,7 +1069,6 @@ begin
 	_advance_token();
 
 	_write_c('\n');
-
 end;
 
 proc _compile_designator();
@@ -1167,6 +1132,19 @@ begin
 	_write_c(')');
 end;
 
+proc _compile_return_statement();
+begin
+	# Skip "return" keyword and whitespace after it.
+	_advance_token(7);
+	_compile_expression();
+
+	_write_z(@asm_mv);
+	_write_register('a', 0);
+	_write_z(@asm_comma);
+	_write_register('t', 0);
+
+end;
+
 proc _compile_statement();
 begin
 	# This is a call if the statement starts with an underscore.
@@ -1185,6 +1163,10 @@ begin
 	li t1, 'v'
 	beq t0, t1, .compile_statement_assignment
 
+	# keyword_ret contains "\tret", so it's 4 bytes long.
+	_memcmp(source_code_position, @keyword_ret, 4);
+	beqz a0, .compile_statement_return
+
 	_compile_line();
 	goto .compile_statement_end;
 
@@ -1206,9 +1188,15 @@ begin
 
 	goto .compile_statement_semicolon;
 
+.compile_statement_return:
+	_advance_token(1);
+	_compile_return_statement();
+	_write_c('\n');
+
+	goto .compile_statement_end;
+
 .compile_statement_semicolon:
 	_advance_token(2);
-
 	_write_c('\n');
 
 .compile_statement_end:
@@ -1235,48 +1223,33 @@ end;
 # a1 - Register number.
 proc _write_register();
 begin
-	sw a0, 0(sp)
-	sw a1, 4(sp)
-
-	_write_c();
-
-	lw a0, 4(sp)
-	li t0, '0'
-	add a0, a0, t0
-	_write_c();
+	_write_c(v88);
+	v84 := v84 + '0';
+	_write_c(v84);
 end;
 
 proc _compile_procedure_prologue();
 begin
 	_write_z(@asm_prologue);
-
 	v0 := 0;
 
 .compile_procedure_prologue_loop:
 	_write_z(@asm_sw);
-
-	li a0, 'a'
-	lw a1, 0(sp)
-	_write_register();
-
+	_write_register('a', v0);
 	_write_z(@asm_comma);
 
 	# Calculate the stack offset: 88 - (4 * parameter_counter)
-	lw t0, 0(sp)
-	li t1, 4
-	mul t0, t0, t1
-	li t1, 88
-	sub a0, t1, t0
-	_write_i();
+	v4 := v0 * 4;
+	v4 := 88 + -v4;
+	_write_i(v4);
 
 	_write_c('(');
 	_write_z(@asm_sp);
 	_write_c(')');
 	_write_c('\n');
 
+	v0 := v0 + 1;
 	lw a0, 0(sp)
-	addi a0, a0, 1
-	sw a0, 0(sp)
 
 	li t0, 8
 	bne a0, t0, .compile_procedure_prologue_loop
@@ -1295,18 +1268,14 @@ begin
 	_write_z();
 
 	_write_token(v0);
-
 	_write_z(@asm_type_function);
 
 	# 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();
+	_advance_token(v0 + 10);
 
 	_compile_procedure_prologue();
 	_compile_procedure_body();
@@ -1334,9 +1303,6 @@ begin
 
 	# 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