nooc

commit dcdf77176b840cf4bea9974a51614bfdaf888a87
parent 55c2f96d993d3f08226d66b284fa6cc92b0130ec
Author: Nihal Jere <nihal@nihaljere.xyz>
Date:   Tue, 23 Nov 2021 18:36:22 -0600

subtraction

Diffstat:
M
main.c
 | 
23
+++++++++++++++++++++++
M
nooc.h
 | 
2
++
M
prog.nc
 | 
2
+-
M
x64.c
 | 
14
++++++++++++++
M
x64.h
 | 
1
+

5 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/main.c b/main.c
@@ -75,6 +75,10 @@ lex(struct slice start)
 			cur->type = TOK_PLUS;
 			start.ptr++;
 			start.len--;
+		} else if (*start.ptr == '-') {
+			cur->type = TOK_MINUS;
+			start.ptr++;
+			start.len--;
 		} else if (*start.ptr == '=') {
 			cur->type = TOK_EQUAL;
 			start.ptr++;
@@ -184,6 +188,9 @@ dumpbinop(enum binop op)
 	case OP_PLUS:
 		fprintf(stderr, "OP_PLUS");
 		break;
+	case OP_MINUS:
+		fprintf(stderr, "OP_MINUS");
+		break;
 	default:
 		error("invalid binop");
 	}
@@ -238,6 +245,13 @@ parseexpr(struct token **tok)
 		expr.left = parseexpr(tok);
 		expr.right = parseexpr(tok);
 		break;
+	case TOK_MINUS:
+		expr.kind = EXPR_BINARY;
+		expr.d.op = OP_MINUS;
+		*tok = (*tok)->next;
+		expr.left = parseexpr(tok);
+		expr.right = parseexpr(tok);
+		break;
 	case TOK_STRING:
 		expr.kind = EXPR_LIT;
 		expr.d.v.type = P_STR;
@@ -330,6 +344,15 @@ genexpr(char *buf, size_t idx, enum reg reg)
 			freereg(rreg);
 			break;
 		}
+		case OP_MINUS: {
+			len += genexpr(ptr ? ptr + len : ptr, expr->left, reg);
+			enum reg rreg = getreg();
+			len += genexpr(ptr ? ptr + len : ptr, expr->right, rreg);
+
+			len += sub_r64_r64(ptr ? ptr + len : ptr, reg, rreg);
+			freereg(rreg);
+			break;
+		}
 		default:
 			error("genexpr: unknown binary op!");
 		}
diff --git a/nooc.h b/nooc.h
@@ -8,6 +8,7 @@ enum tokentype {
 	TOK_RPAREN,
 
 	TOK_PLUS,
+	TOK_MINUS,
 
 	TOK_COMMA,
 	TOK_EQUAL,
@@ -80,6 +81,7 @@ enum primitive {
 
 enum binop {
 	OP_PLUS,
+	OP_MINUS,
 };
 
 struct value {
diff --git a/prog.nc b/prog.nc
@@ -3,6 +3,6 @@ stdout = 0
 exit = 60
 len1 = 11
 len2 = 6
-syscall(write, + + 0 1 + 0 1, "hello world", + 1 + 2 + 3 + 4 1)
+syscall(write, - 2 1, "hello world", + 1 + 2 + 3 + 4 1)
 syscall(write, stdout, " world", len2)
 syscall(exit, 0)
diff --git a/x64.c b/x64.c
@@ -103,3 +103,17 @@ add_r64_r64(char *buf, enum reg reg1, enum reg reg2)
 
 	return 3;
 }
+
+size_t
+sub_r64_r64(char *buf, enum reg reg1, enum reg reg2)
+{
+	uint8_t mov[] = {0x48, 0x29};
+	uint8_t op = (MOD_DIRECT << 6) | (reg1 << 3) | reg2;
+	if (buf) {
+		memcpy(buf, mov, 2);
+		buf += 2;
+		*(buf++) = op;
+	}
+
+	return 3;
+}
diff --git a/x64.h b/x64.h
@@ -35,3 +35,4 @@ size_t add_r_imm(char *buf, enum reg reg, uint64_t imm);
 size_t mov_r_imm(char *buf, enum reg reg, uint64_t imm);
 size_t mov_r64_m64(char *buf, enum reg reg, uint64_t addr);
 size_t add_r64_r64(char *buf, enum reg reg1, enum reg reg2);
+size_t sub_r64_r64(char *buf, enum reg reg1, enum reg reg2);