From the Intel's manual - Instruction Set Reference, the JE
and JZ
have the same opcode (74
for rel8 / 0F 84
for rel 16/32) also JNE
and JNZ
(75
for rel8 / 0F 85
for rel 16/32) share opcodes.
JE
and JZ
they both check for the ZF
(or zero flag), although the manual differs slightly in the descriptions of the first JE
rel8 and JZ
rel8 ZF
usage, but basically they are the same.
Here is an extract from the manual's pages 464, 465 and 467.
Op Code | mnemonic | Description
-----------|-----------|-----------------------------------------------
74 cb | JE rel8 | Jump short if equal (ZF=1).
74 cb | JZ rel8 | Jump short if zero (ZF ? 1).
0F 84 cw | JE rel16 | Jump near if equal (ZF=1). Not supported in 64-bit mode.
0F 84 cw | JZ rel16 | Jump near if 0 (ZF=1). Not supported in 64-bit mode.
0F 84 cd | JE rel32 | Jump near if equal (ZF=1).
0F 84 cd | JZ rel32 | Jump near if 0 (ZF=1).
75 cb | JNE rel8 | Jump short if not equal (ZF=0).
75 cb | JNZ rel8 | Jump short if not zero (ZF=0).
0F 85 cd | JNE rel32 | Jump near if not equal (ZF=0).
0F 85 cd | JNZ rel32 | Jump near if not zero (ZF=0).