Cheat Engine

ciglipaf · How do I cheat? Reputation: 0 Joined: 26 Jul 2015 Posts: 6

i compare two float numbers but fcom gives me wrong results.

justa_dude · Posted: Thu Aug 06, 2015 5:57 pm Post subject:

You evidently have to move the fpu status word to mem, then check its flags. See http://stackoverflow.com/a/7195713.

Zanzer · Posted: Thu Aug 06, 2015 6:03 pm Post subject:

Don't forget to pop the stack too...

gameplayer · Posted: Thu Aug 06, 2015 7:20 pm Post subject:

You must store float-point status word into ax register and use "test ah,..." instruction. I couldn't remember exactly how to use the constants that follow in the "test" instruction. The code should be similar to the following
fcom st(0),st(1)
fnstsw ax
test ah,40 //the constant may be 40, 41 or 01
jne yes_equal

mgr.inz.Player · Posted: Fri Aug 07, 2015 7:59 am Post subject:

Better use fcomi or fcomip.

And then use those jumps:
- JA, JNBE
- JAE, JNB, JNC
- JB, JNAE, JC
- JBE, JNA
- JE, JZ,
- JNE, JNZ

fcomi(p) sets only ZF, PF and CF flags. Above conditional jumps check those flags.

Do not use JG, JL, etc... (those check SF flag and other flags)

If you are perfectly sure that values you want to compare are always: bigger than zero, and those values aren't very high, something less than 1E8, you can use simple CMP and JA, JB, like before.

Example1:
fld [value1] // this value1 can be anything
fld [value2] // this value2 can be anything
fcomip st(0),st(1) // compare
fstp st(0)
je, ja, jb, ....

Example2:
mov eax,[value1] // this value1 is between 0 and 1E8
cmp eax,[value2] // this value2 is between 0 and 1E8
je, ja, jb, ...