primary function call
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@ -78,7 +78,8 @@ $ sh boot.sh
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- 函数和数组不是类型系统的一部分。
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- 可以认为数组的类型就是其元素对应的指针类型。
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- 函数保存了其返回值的类型，建议仅用于直接调用，其它操作可视为 UB。
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- 函数的参数类型和个数不会检查，返回值会参与类型检查。
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- 函数名只能被用于调用，函数调用被视为初等表达式。
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- 数组只支持一维数组，且数组的元素不能是指针类型。
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- 全局变量不能是指针类型。
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- 整数和字符字面量的类型是 `int`，字符串字面量的类型是 `char*`
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@ -95,7 +96,8 @@ $ sh boot.sh
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| 运算符 | 含义 | 结合性 |
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| --------------------------------- | ----------------------------------------------- | -------- |
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| `++` `--` `()` `[]` | 后缀自增自减 函数调用 数组下标 | 从左到右 |
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| `()` | 初等表达式（字面量、标识符、函数调用、括号） | |
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| `++` `--` `[]` | 后缀自增自减 数组下标 | 从左到右 |
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| `++` `--` `+` `-` `*` `&` `!` `~` | 前缀自增自减 正负号 取地址 解引用 逻辑非 按位非 | 从右到左 |
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| `*` `/` `%` | 乘除余 | 从左到右 |
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| `+` `-` | 加减 | 从左到右 |
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@ -106,7 +108,7 @@ $ sh boot.sh
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| `^` | 按位异或 | 从左到右 |
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| <code>|</code> | 按位或 | 从左到右 |
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| `&&` | 逻辑与 | 从左到右 |
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| <code>||</code> | 逻辑或 | 从左到右 |
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| <code>||</code> | 逻辑或 | 从左到右 |
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| `=` | 赋值 | 从右到左 |
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- 同级表达式的求值顺序与结合性一致。
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@ -116,7 +118,6 @@ $ sh boot.sh
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- 逻辑与和逻辑或支持短路求值。
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- 表达式没有左值和右值之分。可以认为右值总是存在一个临时的变量中。
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- 赋值不检查类型。强制类型转换可以用赋值给特定类型的变量实现。
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- 函数的参数类型和个数不会检查，返回值会参与类型检查。
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### 其它支持与不支持
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76
boot.c
76
boot.c
@ -80,7 +80,6 @@ const int TYPE_INT_PTR = 17;
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const int TYPE_CHAR_PTR = 18;
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const int TYPE_PTR_MASK = 16;
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const int TYPE_FUNC_MASK = 32;
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const int TYPE_TOKEN_MASK = 128;
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int parse_int(int ch) {
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@ -436,6 +435,7 @@ int max_local_id = 2;
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const int MARKER_TEMP = 0;
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const int MARKER_SCALAR = 1;
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const int MARKER_ARRAY = 2;
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const int MARKER_FUNCTION = 3;
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int local_marker[4096];
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int global_marker[4096];
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@ -552,7 +552,7 @@ void load(int rd, int id) {
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const char* op = "lw"; // int
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if (type == TYPE_CHAR) {
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op = "lb";
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} else if (type & TYPE_PTR_MASK || type & TYPE_FUNC_MASK) {
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} else if (type & TYPE_PTR_MASK) {
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op = "ld";
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}
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printf(" %s t%d, 0(t%d) # id: type %d\n", op, rd, rd, type);
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@ -564,7 +564,7 @@ void store_t0(int id) {
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const char* op = "sw"; // int
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if (type == TYPE_CHAR) {
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op = "sb";
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} else if (type & TYPE_PTR_MASK || type & TYPE_FUNC_MASK) {
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} else if (type & TYPE_PTR_MASK) {
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op = "sd";
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}
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printf(" %s t0, 0(t1) # id: type %d\n", op, type);
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@ -593,6 +593,10 @@ int lookup(int id) {
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}
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const char* name = id_table + id_lut[id];
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if (global_marker[id]) {
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if (global_marker[id] == MARKER_FUNCTION) {
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eprintf("function name must not appear outside function call: %s\n", name);
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exit(1);
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}
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printf(" la t0, %s # id: %d\n", name, id);
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int reg = materialize_t0(global_type[id] | TYPE_PTR_MASK);
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if (global_marker[id] == MARKER_SCALAR) {
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@ -631,7 +635,7 @@ int asm_r(const char* op, int rs1) {
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}
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int asm_r_arith(const char* op, int rs1) {
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if (local_type[rs1] & TYPE_PTR_MASK || local_type[rs1] & TYPE_FUNC_MASK) {
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if (local_type[rs1] & TYPE_PTR_MASK) {
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eprintf("pointer cannot be arithmetically operated by %s\n", op);
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exit(1);
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}
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@ -654,8 +658,7 @@ int asm_rr(const char* op, int rs1, int rs2) {
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}
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int asm_rr_arith(const char* op, int rs1, int rs2) {
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if (local_type[rs1] & TYPE_PTR_MASK || local_type[rs2] & TYPE_PTR_MASK
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|| local_type[rs1] & TYPE_FUNC_MASK || local_type[rs2] & TYPE_FUNC_MASK) {
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if (local_type[rs1] & TYPE_PTR_MASK || local_type[rs2] & TYPE_PTR_MASK) {
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eprintf("pointer cannot be arithmetically operated by %s\n", op);
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exit(1);
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}
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@ -778,29 +781,12 @@ int asm_sub(int lhs, int rhs) {
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// parser
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int parse_expr();
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int parse_primary_expr() {
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next_token();
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if (token_type == TOKEN_EOF) {
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exit(1);
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} else if (token_type == TOKEN_NUMBER) {
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printf(" li t0, %d\n", token_data);
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return materialize_t0(TYPE_INT);
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} else if (token_type == TOKEN_ID) {
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return lookup(token_data);
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} else if (token_type == TOKEN_STRING) {
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printf(" la t0, .LC%d\n", token_data);
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return materialize_t0(TYPE_CHAR_PTR);
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} else if (token_type == TOKEN_PAREN_LEFT) {
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int reg = parse_expr();
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expect_token(TOKEN_PAREN_RIGHT);
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return reg;
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} else {
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eprintf("unexpected token in primary expression: %d\n", token_type);
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int parse_function_call(int id) {
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const char* name = id_table + id_lut[id];
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if (global_marker[id] != MARKER_FUNCTION) {
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eprintf("not a function name: %s\n", name);
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exit(1);
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}
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}
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int parse_function_call(int func) {
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int arg = 0;
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int args[8];
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while (1) {
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@ -828,9 +814,8 @@ int parse_function_call(int func) {
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load(0, args[i]);
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printf(" mv a%d, t0\n", i);
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}
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load_address(0, func);
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printf(" jalr t0\n");
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int type = local_type[func];
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printf(" call %s\n", name);
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int type = global_type[id];
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if (type != TYPE_VOID) {
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printf(" mv t0, a0\n");
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return materialize_t0(type);
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@ -838,6 +823,33 @@ int parse_function_call(int func) {
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return -1;
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}
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int parse_primary_expr() {
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next_token();
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if (token_type == TOKEN_EOF) {
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exit(1);
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} else if (token_type == TOKEN_NUMBER) {
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printf(" li t0, %d\n", token_data);
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return materialize_t0(TYPE_INT);
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} else if (token_type == TOKEN_ID) {
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next_token();
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if (token_type == TOKEN_PAREN_LEFT) {
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return parse_function_call(token_data);
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}
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unget_token();
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return lookup(token_data);
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} else if (token_type == TOKEN_STRING) {
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printf(" la t0, .LC%d\n", token_data);
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return materialize_t0(TYPE_CHAR_PTR);
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} else if (token_type == TOKEN_PAREN_LEFT) {
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int reg = parse_expr();
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expect_token(TOKEN_PAREN_RIGHT);
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return reg;
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} else {
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eprintf("unexpected token in primary expression: %d\n", token_type);
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exit(1);
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}
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}
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int parse_postfix_expr() {
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int lhs = parse_primary_expr();
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while (1) {
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@ -862,8 +874,6 @@ int parse_postfix_expr() {
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int rhs = parse_expr();
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expect_token(TOKEN_BRACKET_RIGHT);
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lhs = dereference(asm_add(lhs, rhs));
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} else if (token_type == TOKEN_PAREN_LEFT) {
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lhs = parse_function_call(lhs);
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} else {
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unget_token();
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break;
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@ -1440,7 +1450,7 @@ void parse_global_declaration() {
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char* name = id_table + id_lut[id];
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next_token();
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if (token_type == TOKEN_PAREN_LEFT) {
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declare_global(id, MARKER_SCALAR, type | TYPE_FUNC_MASK);
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declare_global(id, MARKER_FUNCTION, type);
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parse_function(name);
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} else {
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declare_global(id, MARKER_SCALAR, type);
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