If part of the assembly code is as following:
xor %ebp,%ebx
jle some address
does this jle means that it will jump when (%ebx ^ %ebp == 0) because that would set ZF to 1?
1 Answers
That's one of the ways JLE can be true. The other is SF≠ OF, as per the manual:
https://www.felixcloutier.com/x86/jcc
Since XOR always clears OF, SF != OF reduces to just SF.
jle after a boolean op will be taken if SF | ZF, i.e. if the result is <= 0.
Interesting optimization to avoid test %ebx,%ebx to compare the result against zero (AND or TEST same,same sets FLAGS identically to cmp reg,0).
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