Begin work in %flags.zf et al

src/asm_tables_amd64.cpp

@@ -219,6 +219,42 @@ struct Asm_amd64 {
 		return "<reg>";
 	}
 
+	i32 flag_bit_from_name(String const &name, i32 *width_) {
+		static const struct {String name; i32 bit; } table[] = {
+			{str_lit("cf"),   0}, // Carry
+			{str_lit("pf"),   2}, // Parity
+			{str_lit("af"),   4}, // Auxiliary Carry
+			{str_lit("zf"),   6}, // Zero
+			{str_lit("sf"),   7}, // Sign
+			{str_lit("tf"),   8}, // Trap
+			{str_lit("if"),   9}, // Interrupt Enable
+			{str_lit("df"),  10}, // Direction
+			{str_lit("of"),  11}, // Overflow
+			{str_lit("iopl"),12}, // I/O Privilege Level (2-bit field: bits 12-13, low bit)
+			{str_lit("nt"),  14}, // Nested Task
+			{str_lit("rf"),  16}, // Resume
+			{str_lit("vm"),  17}, // Virtual-8086 Mode
+			{str_lit("ac"),  18}, // Alignment Check / Access Control
+			{str_lit("vif"), 19}, // Virtual Interrupt Flag
+			{str_lit("vip"), 20}, // Virtual Interrupt Pending
+			{str_lit("id"),  21}, // Identification
+		};
+
+		for (auto const &t : table) {
+			if (name == t.name) {
+				if (width_) {
+					if (t.name == "iopl") {
+						*width_ = 2;
+					} else {
+						*width_ = 1;
+					}
+				}
+				return t.bit;
+			}
+		}
+		return -1;
+	}
+
 	struct Clobber {
 		OperandSet      written;
 		OperandSet      read;