Implement if statements

boot/stage1.s

@@ -1,5 +1,8 @@
 .global _start # Program entry point.
+
+# Global variables or registers.
 # s1 - Contains the current position in the source text.
+# s2 - Label counter.
 
 .equ SOURCE_BUFFER_SIZE, 81920
 
@@ -29,10 +32,17 @@ 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_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
 
 .section .bss
 .type source_code, @object
@@ -116,6 +126,14 @@ _build_binary_expression:
 	call _token_compare
 	beqz a0, .L_build_binary_expression_minus
 
+	li t0, '*'
+	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
+
 	j .Lbuild_binary_expression_end
 
 .L_build_binary_expression_equal:
@@ -172,6 +190,16 @@ _build_binary_expression:
 
 	j .Lbuild_binary_expression_end
 
+.L_build_binary_expression_product:
+	addi s1, s1, 1 # 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)
@@ -198,18 +226,19 @@ _build_expression:
 	sw s1, 24(sp)
 	sw a0, 20(sp)
 
-	addi a0, s1, 0
-	lbu a0, (a0)
+	lbu a0, (s1)
+	li t0, '-'
+	beq a0, t0, .Lbuild_expression_negate
+
+	lbu a0, (s1)
 	li t0, '@'
 	beq a0, t0, .Lbuild_expression_address
 
-	addi a0, s1, 0
-	lbu a0, (a0)
+	lbu a0, (s1)
 	call _is_digit
 	bnez a0, .Lbuild_expression_literal
 
-	addi a0, s1, 0
-	lbu a0, (a0)
+	lbu a0, (s1)
 	li t0, '_'
 	beq a0, t0, .Lbuild_expression_call
 
@@ -241,6 +270,17 @@ _build_expression:
 
 	j .Lbuild_expression_advance
 
+.Lbuild_expression_negate:
+	addi s1, s1, 1 # 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_advance
+
 .Lbuild_expression_address:
 	lw t1, 28(sp)
 	li t0, 0x20 # _
@@ -464,26 +504,10 @@ _compile_call:
 
 	# Only 6 arguments are supported with a0-a5.
 	# Save all arguments on the stack so they aren't overriden afterwards.
-	# The offset on the stack always has two digits in this case.
-	li t1, -4
-	mul t1, t0, t1
-	addi t1, t1, 60
-	li t2, 10
-	div t3, t1, t2
-	rem t4, t1, t2
-	addi t3, t3, '0'
-	addi t4, t4, '0'
-
-	sw t3, 8(sp)
-	sw t4, 4(sp)
-
-	addi a0, sp, 8
-	li a1, 1
-	call _write_out
-
-	addi a0, sp, 4
-	li a1, 1
-	call _write_out
+	li a0, -4
+	mul a0, t0, a0
+	addi a0, a0, 60
+	call _printi
 
 	li t0, '\n'
 	sw t0, 8(sp)
@@ -511,52 +535,14 @@ _compile_call:
 .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.
-	lw t0, 12(sp)
-	li t1, 5
-	bgt t0, t1, .Lcompile_call_perform
-
-	li t0, 0x6120776c # lw a
-	sw t0, 4(sp)
-	addi a0, sp, 4
-	li a1, 4
+	la a0, asm_restore_parameters
+	li a1, ASM_RESTORE_PARAMETERS_SIZE
 	call _write_out
 
-	lw t0, 12(sp) # Argument count for a procedure call.
-
-	li t1, -4
-	mul t1, t0, t1
-	addi t1, t1, 60
-	li t2, 10
-	div t3, t1, t2
-	rem t4, t1, t2
-	addi t3, t3, '0'
-	addi t4, t4, '0'
-	addi t0, t0, '0'
-
-	li t5, '\n'
-	sb t5, 11(sp)
-	li t5, 0x29707328 # (sp)
-	sw t5, 7(sp)
-	sb t4, 6(sp)
-	sb t3, 5(sp)
-	li t5, 0x202c # ,_
-	sh t5, 3(sp)
-	sb t0, 2(sp)
-
-	addi a0, sp, 2
-	li a1, 10
-	call _write_out
-
-	lw t0, 12(sp) # Increment.
-	addi t0, t0, 1
-	sw t0, 12(sp)
-
-	j .Lcompile_call_restore
-
 .Lcompile_call_perform:
 	li t0, 0x20
 	sw t0, 8(sp)
-	li t0, 0x6c6c6163
+	li t0, 0x6c6c6163 # call
 	sw t0, 4(sp)
 	addi a0, sp, 4
 	li a1, 5
@@ -566,11 +552,8 @@ _compile_call:
 	lw a1, 16(sp)
 	call _write_out
 
-	li t0, '\n'
-	sw t0, 8(sp)
-	addi a0, sp, 8
-	li a1, 1
-	call _write_out
+	li a0, '\n'
+	call _put_char
 
 	call _skip_spaces
 	addi s1, s1, 1 # Skip the close paren.
@@ -633,6 +616,9 @@ _read_token:
 	li t1, '-'
 	beq t0, t1, .Ltoken_character_single
 
+	li t1, '*'
+	beq t0, t1, .Ltoken_character_single
+
 	li t1, '@'
 	beq t0, t1, .Ltoken_character_single
 # Expect an identifier or a number.
@@ -1325,6 +1311,97 @@ _compile_return:
 	addi sp, sp, 16
 	ret
 
+.type _compile_if, @function
+_compile_if:
+	# Prologue.
+	addi sp, sp, -32
+	sw ra, 28(sp)
+	sw s0, 24(sp)
+	addi s0, sp, 32
+
+	addi s1, s1, 2 # Skip the if.
+	call _skip_spaces
+
+	call _build_binary_expression
+
+	call _skip_spaces
+	addi s1, s1, 4 # Skip the then.
+
+	# if end marker.
+	li t0, 0x00646e65 # end\0
+	sw t0, 20(sp)
+
+	# Label prefix.
+	li t0, 0x66694c2e # .Lif
+	sw t0, 16(sp)
+
+	li t0, 0x202c3061 # a0,_
+	sw t0, 12(sp)
+	li t0, 0x207a7165 # eqz_
+	sw t0, 8(sp)
+	li t0, 0x62626262 # bbbb
+	sb t0, 7(sp)
+
+	addi a0, sp, 7
+	li a1, 13
+	call _write_out
+
+	# Write the label counter.
+	mv a0, s2
+	call _printi
+
+	li a0, '\n'
+	call _put_char
+
+.Lcompile_if_loop:
+	/* DEBUG
+	mv a0, s1
+	li a1, 6
+	call _write_error
+	call _divide_by_zero_error */
+
+	call _skip_spaces
+	call _read_token
+
+	mv a1, a0
+	mv a0, s1
+	addi a2, sp, 20
+	call _token_compare
+
+	beqz a0, .Lcompile_if_end
+
+	call _read_line
+	li a1, 1
+	call _compile_line
+
+	j .Lcompile_if_loop
+
+.Lcompile_if_end:
+	# Write the label prefix.
+	addi a0, sp, 16
+	li a1, 4
+	call _write_out
+
+	# Write the label counter.
+	mv a0, s2
+	call _printi
+
+	# Finalize the label.
+	li t0, 0x0a3a0a3a # :\n:\n
+	sh t0, 12(sp)
+	addi a0, sp, 12
+	li a1, 2
+	call _write_out
+
+	addi s2, s2, 1 # Increment the label counter.
+	addi s1, s1, 4 # Skip the end with newline.
+
+	# Epilogue.
+	lw ra, 28(sp)
+	lw s0, 24(sp)
+	addi sp, sp, 32
+	ret
+
 # Parameters:
 # a0 - Line length.
 # a1 - Whether the section header was already emitted. If not it should be
@@ -1442,6 +1519,14 @@ _compile_line:
 	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
@@ -1450,16 +1535,16 @@ _compile_line:
 
 	j .Lcompile_line_unchanged # Else.
 
+.Lcompile_line_if:
+	call _compile_if
+	j .Lcompile_line_section
+
 .Lcompile_line_label:
 	lw a0, 20(sp)
 	call _compile_label
 	j .Lcompile_line_section
 
 .Lcompile_line_return:
-	/* DEBUG
-	mv a0, s1
-	li a1, 6
-	call _write_error */
 	call _compile_return
 	j .Lcompile_line_section
 
@@ -1659,9 +1744,10 @@ _start:
 	li a1, SOURCE_BUFFER_SIZE # Buffer size.
 	call _read_file
 
+	li s2, 1
 	la s1, source_code # s1 = Source code position.
 	call _compile
 
 	# Call exit.
 	li a0, 0   # Use 0 return code.
-	call exit
+	call _exit