Most compact way to test for a negative number in x86 assembly?
assembly, micro-optimization, x86
Solution
`add eax, eax` is only two bytes (`01 C0` or `03 C0`), but destructive. (check for carry afterwards)
`test eax, eax` is also only two bytes (`85 C0`). (check for sign afterwards)
Problem
Currently I am doing this to test for a negative number in x86 assembly (r/m32,imm8): ``` 83F800 CMP EAX, 0 ``` This can be followed by JL. This is 3 bytes and supposedly clocks at "1/2". I could use TEST EAX, or CMP EAX,imm32 (encoding 3D), both of which clock at "1", but take 5 bytes. In general, if I am trying to minimize code size, is the way I am doing it correct? Once again, this is to test if a number is less than zero.