1 files changed, 195 insertions, 0 deletions
diff --git a/05/codegen.b b/05/codegen.b
new file mode 100644
index 0000000..1507e6d
--- /dev/null
+++ b/05/codegen.b
@@ -0,0 +1,195 @@
+; CALLING CONVENTION:
+;  arguments are pushed onto the stack by the caller, from right to left
+;  caller must also reserve space on stack for return value
+;  so the function puts the return value at [rbp+8]  (+8 for stored return address)
+
+
+
+global code_output
+global codegen_second_pass ; = 0 on first global pass, 1 on second global pass
+global functions_addresses ; ident list of addresses
+global functions_labels ; ident list of ident lists of label addresses
+global curr_function_labels ; ident list of labels for current function (written to in 1st pass, read from in 2nd pass)
+
+#define REG_RAX 0
+#define REG_RBX 3
+#define REG_RCX 1
+#define REG_RDX 2
+#define REG_RSP 4
+#define REG_RBP 5
+#define REG_RSI 6
+#define REG_RDI 7
+
+function emit_byte
+	argument byte
+	*1code_output = byte
+	code_output += 1
+	return
+
+function emit_bytes
+	argument bytes
+	argument count
+	memcpy(code_output, bytes, count)
+	code_output += count
+	return
+	
+function emit_word
+	argument word
+	*2code_output = word
+	code_output += 2
+	return
+
+function emit_dword
+	argument word
+	*4code_output = word
+	code_output += 4
+	return
+
+function emit_qword
+	argument word
+	*8code_output = word
+	code_output += 8
+	return
+
+; e.g. emit_mov_reg(REG_RAX, REG_RBX)  emits  mov rax, rbx
+function emit_mov_reg
+	argument dest
+	argument src
+	local n
+	
+	;48 89 (DEST|SRC<<3|0xc0)
+	*2code_output = 0x8948
+	code_output += 2
+	n = 0xc0 | dest
+	n |= src < 3
+	*1code_output = n
+	code_output += 1
+	return
+	
+
+function emit_sub_rsp_imm32
+	argument imm32
+	;48 81 ec IMM32
+	*2code_output = 0x8148
+	code_output += 2
+	*1code_output = 0xec
+	code_output += 1
+	*4code_output = imm32
+	code_output += 4
+	return
+
+function emit_mov_qword_rsp_rbp
+	; 48 89 2c 24
+	*4code_output = 0x242c8948
+	code_output += 4
+	return
+
+function emit_mov_rbp_qword_rsp
+	; 48 8b 2c 24
+	*4code_output = 0x242c8b48
+	code_output += 4
+	return
+
+function emit_add_rsp_imm32
+	argument imm32
+	;48 81 c4 IMM32
+	*2code_output = 0x8148
+	code_output += 2
+	*1code_output = 0xc4
+	code_output += 1
+	*4code_output = imm32
+	code_output += 4
+	return
+
+function emit_ret
+	*1code_output = 0xc3
+	code_output += 1
+	return
+
+; make sure you put the return value in the proper place before calling this
+function generate_return
+	emit_mov_reg(REG_RSP, REG_RBP)
+	emit_mov_rbp_qword_rsp()
+	emit_add_rsp_imm32(8)
+	emit_ret()
+	return
+
+function generate_statement
+	argument statement
+	; @TODO
+	return
+
+function generate_function
+	argument function_name
+	argument function_statement
+	local out0
+	
+	if codegen_second_pass != 0 goto genf_second_pass
+		curr_function_labels = ident_list_create(4000) ; ~ 200 labels per function should be plenty
+		ident_list_add(functions_labels, function_name, curr_function_labels)
+		goto genf_cont
+	:genf_second_pass
+		curr_function_labels = ident_list_lookup(functions_labels, function_name)
+	:genf_cont
+	
+	; prologue
+	emit_sub_rsp_imm32(8)
+	emit_mov_qword_rsp_rbp()
+	emit_mov_reg(REG_RBP, REG_RSP)	
+	
+	generate_statement(function_statement)
+	
+	; implicit return at end of function
+	generate_return()
+	
+	return
+
+function generate_functions
+	local addr
+	local c
+	local p
+	local function_name
+	
+	function_name = function_statements
+	
+	:genfunctions_loop
+		if *1function_name == 0 goto genfunctions_loop_end
+		addr = code_output - output_file_data ; address of this function
+		if codegen_second_pass != 0 goto genfs_check_addr
+			; first pass; record address of function
+			ident_list_add(functions_addresses, function_name, addr)
+			goto genfs_cont
+		:genfs_check_addr
+			c = ident_list_lookup(functions_addresses, function_name)
+			if c != addr goto function_addr_mismatch
+			goto genfs_cont
+		:genfs_cont
+		p = memchr(function_name, 0)
+		p += 1
+		generate_function(function_name, p)
+		function_name = p + 8
+		goto genfunctions_loop
+	:genfunctions_loop_end
+	return
+	
+	:function_addr_mismatch
+		; address of function on 2nd pass doesn't line up with 1st pass
+		fputs(2, .str_function_addr_mismatch)
+		fputs(2, function_name)
+		exit(1)
+	:str_function_addr_mismatch
+		string Function address on first pass doesn't match 2nd pass:
+		byte 32
+		byte 0
+
+function generate_code
+	local p_func
+	code_output = output_file_data + FUNCTIONS_ADDR
+	codegen_second_pass = 0
+	generate_functions()
+	code_output = output_file_data + FUNCTIONS_ADDR
+	codegen_second_pass = 1
+	generate_functions()
+	; generate code at the entry point of the executable
+	; @TODO
+	return