Performance in conditional statements - c

Question

I noticed that a code I'm working on uses conditionals like:
if(A != val) {
// code B
}
if(B != val) {
// code A
}
But to me, reading the same code like below is much easier. Maybe a personal preference.
if( B == val) {
//code B
}
if( A == val) {
//code A
}
This is a very latency sensitive code so is there a performance difference between the two? Is there a performance difference between != or == ? or > or < for that matter? Also, I realize that this code leaves room for a 3rd condition though I'm pretty sure the code leaves only 2 paths possible so an if/else is more appropriate.
Much appreciated.

Answer 1

Here is the assembly code when in the condition you use !=, note that I added a printf inside the if statement in order to have a better output from gdb:
0x0000000000400526 <+0>: push rbp
0x0000000000400527 <+1>: mov rbp,rsp
0x000000000040052a <+4>: sub rsp,0x10
0x000000000040052e <+8>: mov DWORD PTR [rbp-0xc],0x0
0x0000000000400535 <+15>: mov DWORD PTR [rbp-0x8],0x1
0x000000000040053c <+22>: mov DWORD PTR [rbp-0x4],0x1
0x0000000000400543 <+29>: mov eax,DWORD PTR [rbp-0xc]
0x0000000000400546 <+32>: cmp eax,DWORD PTR [rbp-0x4]
0x0000000000400549 <+35>: **je** 0x400555 <main+47>
0x000000000040054b <+37>: mov edi,0x4005f4
0x0000000000400550 <+42>: call 0x400400 <puts#plt>
0x0000000000400555 <+47>: mov eax,DWORD PTR [rbp-0x8]
0x0000000000400558 <+50>: cmp eax,DWORD PTR [rbp-0x4]
0x000000000040055b <+53>: **je** 0x400567 <main+65>
0x000000000040055d <+55>: mov edi,0x4005f4
0x0000000000400562 <+60>: call 0x400400 <puts#plt>
0x0000000000400567 <+65>: mov eax,0x0
0x000000000040056c <+70>: leave
0x000000000040056d <+71>: ret
While this is for ==:
0x0000000000400526 <+0>: push rbp
0x0000000000400527 <+1>: mov rbp,rsp
0x000000000040052a <+4>: sub rsp,0x10
0x000000000040052e <+8>: mov DWORD PTR [rbp-0xc],0x0
0x0000000000400535 <+15>: mov DWORD PTR [rbp-0x8],0x1
0x000000000040053c <+22>: mov DWORD PTR [rbp-0x4],0x1
0x0000000000400543 <+29>: mov eax,DWORD PTR [rbp-0x8]
0x0000000000400546 <+32>: cmp eax,DWORD PTR [rbp-0x4]
0x0000000000400549 <+35>: **jne** 0x400555 <main+47>
0x000000000040054b <+37>: mov edi,0x4005f4
0x0000000000400550 <+42>: call 0x400400 <puts#plt>
0x0000000000400555 <+47>: mov eax,DWORD PTR [rbp-0xc]
0x0000000000400558 <+50>: cmp eax,DWORD PTR [rbp-0x4]
0x000000000040055b <+53>: **jne** 0x400567 <main+65>
0x000000000040055d <+55>: mov edi,0x4005f4
0x0000000000400562 <+60>: call 0x400400 <puts#plt>
0x0000000000400567 <+65>: mov eax,0x0
0x000000000040056c <+70>: leave
0x000000000040056d <+71>: ret
As you may notice the only difference is the usage of je (jump if equal) or jne (jump if not equal) so in terms of performance you could say that it' exactly the same

Answer 2

You will have a conditional jump in your assembler code whether you check for equality or any kind of unequality. Performance difference should be marginal.
Though it can be beneficial to write branchless code, see e.g. Why is it faster to process a sorted array than an unsorted array?.