1 files changed, 2 insertions, 5 deletions
diff --git a/disasm.c b/disasm.c
index 4a39c4f..43f78db 100644
--- a/disasm.c
+++ b/disasm.c
@@ -51,10 +51,7 @@ void disasm(struct sux *cpu, uint8_t lines, uint8_t opcode, uint8_t prefix, uint
 		case IMM :
 		case REL : addrsize = (1 << rs)-1; break;
 	}
-
-	for (uint8_t i = 0; i < addrsize+1; i++) {
-		mask.u8[i] = (i == addrsize && addrsize != 0xFF) ? 0x7F : 0xFF;
-	}
+	mask.u64 = (-(uint64_t)1 >> ((7 - addrsize) * 8));
 	value = read_value(cpu, 0, cpu->pc, addrsize, 0, 0);
 	if ((prefix >> 6) == 1 || (prefix >> 6) == 2 || optype[opcode] == REL) {
 		switch (addrsize) {
@@ -67,7 +64,7 @@ void disasm(struct sux *cpu, uint8_t lines, uint8_t opcode, uint8_t prefix, uint
 			case 6 :
 			case 7 : sign = ((int64_t)value < 0) ? "-" : "+"; break;
 		}
-		value &= mask.u64;
+		value = (sign[0] == '-') ? (~value + 1) & mask.u64 : value;
 	}
 	switch (optype[opcode]) {
 		case BREG: