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pointer subtract

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Yaossg 2024-11-16 23:45:57 +08:00
parent cf4c851aad
commit cb7b0e2a76
1 changed files with 26 additions and 4 deletions
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30
boot.c
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@ -682,9 +682,9 @@ int step_of(int type) {
return 1;
}
void asm_slli_t0(int type) {
void asm_shift_t0(const char* op, int type) {
if (type == TYPE_INT_PTR) {
printf(" slli t0, t0, 2\n");
printf(" %s t0, t0, 2\n", op);
}
}
@ -704,7 +704,7 @@ int asm_add(int lhs, int rhs) {
int ptr_type = local_type[ptr];
load(0, idx);
load(1, ptr);
asm_slli_t0(ptr_type);
asm_shift_t0("slli", ptr_type);
printf(" add t0, t0, t1\n");
return materialize_t0(ptr_type);
}
@ -715,6 +715,28 @@ int asm_add(int lhs, int rhs) {
return asm_rr("add", lhs, rhs);
}
int asm_sub(int lhs, int rhs) {
int type1 = local_type[lhs] & TYPE_PTR_MASK;
int type2 = local_type[rhs] & TYPE_PTR_MASK;
if (type1 && type2) {
load(0, lhs);
load(1, rhs);
int ptr_type = local_type[lhs];
printf(" sub t0, t0, t1\n");
asm_shift_t0("srli", ptr_type);
return materialize_t0(TYPE_INT);
}
if (type1) {
int neg = asm_r("neg", rhs);
return asm_add(lhs, neg);
}
if (type2) {
eprintf("a number cannot be subtracted by a pointer\n");
exit(1);
}
return asm_rr("sub", lhs, rhs);
}
// parser
int parse_expr();
@ -870,7 +892,7 @@ int parse_add_expr() {
lhs = asm_add(lhs, rhs);
} else if (token_type == TOKEN_MINUS) {
int rhs = parse_mul_expr();
lhs = asm_rr("sub", lhs, rhs);
lhs = asm_sub(lhs, rhs);
} else {
unget_token();
break;