cmp [rcx],(float)61 vs cmp [rcx],rbx, different result

[oLaudix]

When I manualy compare [rcx] (that holds 61 in float) to (float)61 it passes the compare without a problem:



but when I'm doing compare to a register that is 61 in float the check fails:



What am I doing wrong?

[sub1to]

One issue is that rbx is a 64 bit register, so it will compare the upper 32bits of rbx against the bits that are in memory pointed at by rcx. You should compare it against a 32bit register instead:

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cmp [rcx], ebx

[SunBeam]

I strongly suggest using SSE/SSE2 instructions, as we're in 2023:

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code:
xorps xmm14,xmm14 // if you wanna have it clean, although it doesn't matter
movss xmm14,[myFloat]
cmpss xmm14,[rcx]
jne bla

myFloat:
dd (float)2.0

You can safely use xmm10...xmm15, as I doubt you'll find a game/program with functions that have that many args.