This brought back memories of some 40 years ago during my first steps learning x86 assembly language, realising the first comment: [Wayback/Archive] assembly – Difference between JE/JNE and JZ/JNZ – Stack Overflow
Q
In x86 assembly code, are
JEandJNEexactly the same asJZandJNZ?C
Long answer: yes.
C
TL:DR: same machine operation, different semantic meaning. Just like
jb/jc/jnaeall testing CF=1. See felixcloutier.com/x86/jcc
Merry X-mas everyone!
And thanks [Wayback/Archive] Daniel Hanrahan for asking, [Wayback/Archive] Hans Passant and [Wayback/Archive] Peter Cordes for commenting.
Be sure to read the rest of the comments and answers to read on the WHY these instructions are the same. That insight made me realise I was finally understanding the x86 architecture at a deeper level.
Related:
- [WaybackSave/Archive] Intel® 64 and IA-32 Architectures Software Developer’s Manual Combined Volumes 2A, 2B, 2C, and 2D: Instruction Set Reference, A-Z
- [Wayback/Archive] Jcc — Jump if Condition Is Met
Sorted by Opcode column (with a little bit of help from Excel, Notepad++ and [Wayback/Archive] HTML Tables generator – TablesGenerator.com; then bolded or italicised the Description column of equivalent entries:
Opcode Instruction Op/En 64-Bit Mode Compat/Leg Mode Description 0F 80 cd JO rel32 D Valid Valid Jump near if overflow (OF=1). 0F 80 cw JO rel16 D N.S. Valid Jump near if overflow (OF=1). Not supported in 64-bit mode. 0F 81 cd JNO rel32 D Valid Valid Jump near if not overflow (OF=0). 0F 81 cw JNO rel16 D N.S. Valid Jump near if not overflow (OF=0). Not supported in 64-bit mode. 0F 82 cd JB rel32 D Valid Valid Jump near if below (CF=1). 0F 82 cd JC rel32 D Valid Valid Jump near if carry (CF=1). 0F 82 cd JNAE rel32 D Valid Valid Jump near if not above or equal (CF=1). 0F 82 cw JB rel16 D N.S. Valid Jump near if below (CF=1). Not supported in 64-bit mode. 0F 82 cw JC rel16 D N.S. Valid Jump near if carry (CF=1). Not supported in 64-bit mode. 0F 82 cw JNAE rel16 D N.S. Valid Jump near if not above or equal (CF=1). Not supported in 64-bit mode. 0F 83 cd JAE rel32 D Valid Valid Jump near if above or equal (CF=0). 0F 83 cd JNB rel32 D Valid Valid Jump near if not below (CF=0). 0F 83 cd JNC rel32 D Valid Valid Jump near if not carry (CF=0). 0F 83 cw JAE rel16 D N.S. Valid Jump near if above or equal (CF=0). Not supported in 64-bit mode. 0F 83 cw JNB rel16 D N.S. Valid Jump near if not below (CF=0). Not supported in 64-bit mode. 0F 83 cw JNC rel16 D N.S. Valid Jump near if not carry (CF=0). Not supported in 64-bit mode. 0F 84 cd JE rel32 D Valid Valid Jump near if equal (ZF=1). 0F 84 cd JZ rel32 D Valid Valid Jump near if 0 (ZF=1). 0F 84 cd JZ rel32 D Valid Valid Jump near if 0 (ZF=1). 0F 84 cw JE rel16 D N.S. Valid Jump near if equal (ZF=1). Not supported in 64-bit mode. 0F 84 cw JZ rel16 D N.S. Valid Jump near if 0 (ZF=1). Not supported in 64-bit mode. 0F 84 cw JZ rel16 D N.S. Valid Jump near if 0 (ZF=1). Not supported in 64-bit mode. 0F 85 cd JNE rel32 D Valid Valid Jump near if not equal (ZF=0). 0F 85 cd JNZ rel32 D Valid Valid Jump near if not zero (ZF=0). 0F 85 cw JNE rel16 D N.S. Valid Jump near if not equal (ZF=0). Not supported in 64-bit mode. 0F 85 cw JNZ rel16 D N.S. Valid Jump near if not zero (ZF=0). Not supported in 64-bit mode. 0F 86 cd JBE rel32 D Valid Valid Jump near if below or equal (CF=1 or ZF=1). 0F 86 cd JNA rel32 D Valid Valid Jump near if not above (CF=1 or ZF=1). 0F 86 cw JBE rel16 D N.S. Valid Jump near if below or equal (CF=1 or ZF=1). Not supported in 64-bit mode. 0F 86 cw JNA rel16 D N.S. Valid Jump near if not above (CF=1 or ZF=1). Not supported in 64-bit mode. 0F 87 cd JA rel32 D Valid Valid Jump near if above (CF=0 and ZF=0). 0F 87 cd JNBE rel32 D Valid Valid Jump near if not below or equal (CF=0 and ZF=0). 0F 87 cw JA rel16 D N.S. Valid Jump near if above (CF=0 and ZF=0). Not supported in 64-bit mode. 0F 87 cw JNBE rel16 D N.S. Valid Jump near if not below or equal (CF=0 and ZF=0). Not supported in 64-bit mode. 0F 88 cd JS rel32 D Valid Valid Jump near if sign (SF=1). 0F 88 cw JS rel16 D N.S. Valid Jump near if sign (SF=1). Not supported in 64-bit mode. 0F 89 cd JNS rel32 D Valid Valid Jump near if not sign (SF=0). 0F 89 cw JNS rel16 D N.S. Valid Jump near if not sign (SF=0). Not supported in 64-bit mode. 0F 8A cd JP rel32 D Valid Valid Jump near if parity (PF=1). 0F 8A cd JPE rel32 D Valid Valid Jump near if parity even (PF=1). 0F 8A cw JP rel16 D N.S. Valid Jump near if parity (PF=1). Not supported in 64-bit mode. 0F 8A cw JPE rel16 D N.S. Valid Jump near if parity even (PF=1). Not supported in 64-bit mode. 0F 8B cd JNP rel32 D Valid Valid Jump near if not parity (PF=0). 0F 8B cd JPO rel32 D Valid Valid Jump near if parity odd (PF=0). 0F 8B cw JNP rel16 D N.S. Valid Jump near if not parity (PF=0). Not supported in 64-bit mode. 0F 8B cw JPO rel16 D N.S. Valid Jump near if parity odd (PF=0). Not supported in 64-bit mode. 0F 8C cd JL rel32 D Valid Valid Jump near if less (SF≠ OF). 0F 8C cd JNGE rel32 D Valid Valid Jump near if not greater or equal (SF≠ OF). 0F 8C cw JL rel16 D N.S. Valid Jump near if less (SF≠ OF). Not supported in 64-bit mode. 0F 8C cw JNGE rel16 D N.S. Valid Jump near if not greater or equal (SF≠ OF). Not supported in 64-bit mode. 0F 8D cd JGE rel32 D Valid Valid Jump near if greater or equal (SF=OF). 0F 8D cd JNL rel32 D Valid Valid Jump near if not less (SF=OF). 0F 8D cw JGE rel16 D N.S. Valid Jump near if greater or equal (SF=OF). Not supported in 64-bit mode. 0F 8D cw JNL rel16 D N.S. Valid Jump near if not less (SF=OF). Not supported in 64-bit mode. 0F 8E cd JLE rel32 D Valid Valid Jump near if less or equal (ZF=1 or SF≠ OF). 0F 8E cd JNG rel32 D Valid Valid Jump near if not greater (ZF=1 or SF≠ OF). 0F 8E cw JLE rel16 D N.S. Valid Jump near if less or equal (ZF=1 or SF≠ OF). Not supported in 64-bit mode. 0F 8E cw JNG rel16 D N.S. Valid Jump near if not greater (ZF=1 or SF≠ OF). Not supported in 64-bit mode. 0F 8F cd JG rel32 D Valid Valid Jump near if greater (ZF=0 and SF=OF). 0F 8F cd JNLE rel32 D Valid Valid Jump near if not less or equal (ZF=0 and SF=OF). 0F 8F cw JG rel16 D N.S. Valid Jump near if greater (ZF=0 and SF=OF). Not supported in 64-bit mode. 0F 8F cw JNLE rel16 D N.S. Valid Jump near if not less or equal (ZF=0 and SF=OF). Not supported in 64-bit mode. 70 cb JO rel8 D Valid Valid Jump short if overflow (OF=1). 71 cb JNO rel8 D Valid Valid Jump short if not overflow (OF=0). 72 cb JB rel8 D Valid Valid Jump short if below (CF=1). 72 cb JC rel8 D Valid Valid Jump short if carry (CF=1). 72 cb JNAE rel8 D Valid Valid Jump short if not above or equal (CF=1). 73 cb JAE rel8 D Valid Valid Jump short if above or equal (CF=0). 73 cb JNB rel8 D Valid Valid Jump short if not below (CF=0). 73 cb JNC rel8 D Valid Valid Jump short if not carry (CF=0). 74 cb JE rel8 D Valid Valid Jump short if equal (ZF=1). 74 cb JZ rel8 D Valid Valid Jump short if zero (ZF = 1). 75 cb JNE rel8 D Valid Valid Jump short if not equal (ZF=0). 75 cb JNZ rel8 D Valid Valid Jump short if not zero (ZF=0). 76 cb JBE rel8 D Valid Valid Jump short if below or equal (CF=1 or ZF=1). 76 cb JNA rel8 D Valid Valid Jump short if not above (CF=1 or ZF=1). 77 cb JA rel8 D Valid Valid Jump short if above (CF=0 and ZF=0). 77 cb JNBE rel8 D Valid Valid Jump short if not below or equal (CF=0 and ZF=0). 78 cb JS rel8 D Valid Valid Jump short if sign (SF=1). 79 cb JNS rel8 D Valid Valid Jump short if not sign (SF=0). 7A cb JP rel8 D Valid Valid Jump short if parity (PF=1). 7A cb JPE rel8 D Valid Valid Jump short if parity even (PF=1). 7B cb JNP rel8 D Valid Valid Jump short if not parity (PF=0). 7B cb JPO rel8 D Valid Valid Jump short if parity odd (PF=0). 7C cb JL rel8 D Valid Valid Jump short if less (SF≠ OF). 7C cb JNGE rel8 D Valid Valid Jump short if not greater or equal (SF≠ OF). 7D cb JGE rel8 D Valid Valid Jump short if greater or equal (SF=OF). 7D cb JNL rel8 D Valid Valid Jump short if not less (SF=OF). 7E cb JLE rel8 D Valid Valid Jump short if less or equal (ZF=1 or SF≠ OF). 7E cb JNG rel8 D Valid Valid Jump short if not greater (ZF=1 or SF≠ OF). 7F cb JG rel8 D Valid Valid Jump short if greater (ZF=0 and SF=OF). 7F cb JNLE rel8 D Valid Valid Jump short if not less or equal (ZF=0 and SF=OF). E3 cb JCXZ rel8 D N.E. Valid Jump short if CX register is 0. E3 cb JECXZ rel8 D Valid Valid Jump short if ECX register is 0. E3 cb JRCXZ rel8 D Valid N.E. Jump short if RCX register is 0. Original table from the above Jcc link:
Opcode Instruction Op/En 64-Bit Mode Compat/Leg Mode Description 77 cb JA rel8 D Valid Valid Jump short if above (CF=0 and ZF=0). 73 cb JAE rel8 D Valid Valid Jump short if above or equal (CF=0). 72 cb JB rel8 D Valid Valid Jump short if below (CF=1). 76 cb JBE rel8 D Valid Valid Jump short if below or equal (CF=1 or ZF=1). 72 cb JC rel8 D Valid Valid Jump short if carry (CF=1). E3 cb JCXZ rel8 D N.E. Valid Jump short if CX register is 0. E3 cb JECXZ rel8 D Valid Valid Jump short if ECX register is 0. E3 cb JRCXZ rel8 D Valid N.E. Jump short if RCX register is 0. 74 cb JE rel8 D Valid Valid Jump short if equal (ZF=1). 7F cb JG rel8 D Valid Valid Jump short if greater (ZF=0 and SF=OF). 7D cb JGE rel8 D Valid Valid Jump short if greater or equal (SF=OF). 7C cb JL rel8 D Valid Valid Jump short if less (SF≠ OF). 7E cb JLE rel8 D Valid Valid Jump short if less or equal (ZF=1 or SF≠ OF). 76 cb JNA rel8 D Valid Valid Jump short if not above (CF=1 or ZF=1). 72 cb JNAE rel8 D Valid Valid Jump short if not above or equal (CF=1). 73 cb JNB rel8 D Valid Valid Jump short if not below (CF=0). 77 cb JNBE rel8 D Valid Valid Jump short if not below or equal (CF=0 and ZF=0). 73 cb JNC rel8 D Valid Valid Jump short if not carry (CF=0). 75 cb JNE rel8 D Valid Valid Jump short if not equal (ZF=0). 7E cb JNG rel8 D Valid Valid Jump short if not greater (ZF=1 or SF≠ OF). 7C cb JNGE rel8 D Valid Valid Jump short if not greater or equal (SF≠ OF). 7D cb JNL rel8 D Valid Valid Jump short if not less (SF=OF). 7F cb JNLE rel8 D Valid Valid Jump short if not less or equal (ZF=0 and SF=OF). 71 cb JNO rel8 D Valid Valid Jump short if not overflow (OF=0). 7B cb JNP rel8 D Valid Valid Jump short if not parity (PF=0). 79 cb JNS rel8 D Valid Valid Jump short if not sign (SF=0). 75 cb JNZ rel8 D Valid Valid Jump short if not zero (ZF=0). 70 cb JO rel8 D Valid Valid Jump short if overflow (OF=1). 7A cb JP rel8 D Valid Valid Jump short if parity (PF=1). 7A cb JPE rel8 D Valid Valid Jump short if parity even (PF=1). 7B cb JPO rel8 D Valid Valid Jump short if parity odd (PF=0). 78 cb JS rel8 D Valid Valid Jump short if sign (SF=1). 74 cb JZ rel8 D Valid Valid Jump short if zero (ZF = 1). 0F 87 cw JA rel16 D N.S. Valid Jump near if above (CF=0 and ZF=0). Not supported in 64-bit mode. 0F 87 cd JA rel32 D Valid Valid Jump near if above (CF=0 and ZF=0). 0F 83 cw JAE rel16 D N.S. Valid Jump near if above or equal (CF=0). Not supported in 64-bit mode. 0F 83 cd JAE rel32 D Valid Valid Jump near if above or equal (CF=0). 0F 82 cw JB rel16 D N.S. Valid Jump near if below (CF=1). Not supported in 64-bit mode. 0F 82 cd JB rel32 D Valid Valid Jump near if below (CF=1). 0F 86 cw JBE rel16 D N.S. Valid Jump near if below or equal (CF=1 or ZF=1). Not supported in 64-bit mode. 0F 86 cd JBE rel32 D Valid Valid Jump near if below or equal (CF=1 or ZF=1). 0F 82 cw JC rel16 D N.S. Valid Jump near if carry (CF=1). Not supported in 64-bit mode. 0F 82 cd JC rel32 D Valid Valid Jump near if carry (CF=1). 0F 84 cw JE rel16 D N.S. Valid Jump near if equal (ZF=1). Not supported in 64-bit mode. 0F 84 cd JE rel32 D Valid Valid Jump near if equal (ZF=1). 0F 84 cw JZ rel16 D N.S. Valid Jump near if 0 (ZF=1). Not supported in 64-bit mode. 0F 84 cd JZ rel32 D Valid Valid Jump near if 0 (ZF=1). 0F 8F cw JG rel16 D N.S. Valid Jump near if greater (ZF=0 and SF=OF). Not supported in 64-bit mode. 0F 8F cd JG rel32 D Valid Valid Jump near if greater (ZF=0 and SF=OF). 0F 8D cw JGE rel16 D N.S. Valid Jump near if greater or equal (SF=OF). Not supported in 64-bit mode. 0F 8D cd JGE rel32 D Valid Valid Jump near if greater or equal (SF=OF). 0F 8C cw JL rel16 D N.S. Valid Jump near if less (SF≠ OF). Not supported in 64-bit mode. 0F 8C cd JL rel32 D Valid Valid Jump near if less (SF≠ OF). 0F 8E cw JLE rel16 D N.S. Valid Jump near if less or equal (ZF=1 or SF≠ OF). Not supported in 64-bit mode. 0F 8E cd JLE rel32 D Valid Valid Jump near if less or equal (ZF=1 or SF≠ OF). 0F 86 cw JNA rel16 D N.S. Valid Jump near if not above (CF=1 or ZF=1). Not supported in 64-bit mode. 0F 86 cd JNA rel32 D Valid Valid Jump near if not above (CF=1 or ZF=1). 0F 82 cw JNAE rel16 D N.S. Valid Jump near if not above or equal (CF=1). Not supported in 64-bit mode. 0F 82 cd JNAE rel32 D Valid Valid Jump near if not above or equal (CF=1). 0F 83 cw JNB rel16 D N.S. Valid Jump near if not below (CF=0). Not supported in 64-bit mode. 0F 83 cd JNB rel32 D Valid Valid Jump near if not below (CF=0). 0F 87 cw JNBE rel16 D N.S. Valid Jump near if not below or equal (CF=0 and ZF=0). Not supported in 64-bit mode. 0F 87 cd JNBE rel32 D Valid Valid Jump near if not below or equal (CF=0 and ZF=0). 0F 83 cw JNC rel16 D N.S. Valid Jump near if not carry (CF=0). Not supported in 64-bit mode. 0F 83 cd JNC rel32 D Valid Valid Jump near if not carry (CF=0). 0F 85 cw JNE rel16 D N.S. Valid Jump near if not equal (ZF=0). Not supported in 64-bit mode. 0F 85 cd JNE rel32 D Valid Valid Jump near if not equal (ZF=0). 0F 8E cw JNG rel16 D N.S. Valid Jump near if not greater (ZF=1 or SF≠ OF). Not supported in 64-bit mode. 0F 8E cd JNG rel32 D Valid Valid Jump near if not greater (ZF=1 or SF≠ OF). 0F 8C cw JNGE rel16 D N.S. Valid Jump near if not greater or equal (SF≠ OF). Not supported in 64-bit mode. 0F 8C cd JNGE rel32 D Valid Valid Jump near if not greater or equal (SF≠ OF). 0F 8D cw JNL rel16 D N.S. Valid Jump near if not less (SF=OF). Not supported in 64-bit mode. 0F 8D cd JNL rel32 D Valid Valid Jump near if not less (SF=OF). 0F 8F cw JNLE rel16 D N.S. Valid Jump near if not less or equal (ZF=0 and SF=OF). Not supported in 64-bit mode. 0F 8F cd JNLE rel32 D Valid Valid Jump near if not less or equal (ZF=0 and SF=OF). 0F 81 cw JNO rel16 D N.S. Valid Jump near if not overflow (OF=0). Not supported in 64-bit mode. 0F 81 cd JNO rel32 D Valid Valid Jump near if not overflow (OF=0). 0F 8B cw JNP rel16 D N.S. Valid Jump near if not parity (PF=0). Not supported in 64-bit mode. 0F 8B cd JNP rel32 D Valid Valid Jump near if not parity (PF=0). 0F 89 cw JNS rel16 D N.S. Valid Jump near if not sign (SF=0). Not supported in 64-bit mode. 0F 89 cd JNS rel32 D Valid Valid Jump near if not sign (SF=0). 0F 85 cw JNZ rel16 D N.S. Valid Jump near if not zero (ZF=0). Not supported in 64-bit mode. 0F 85 cd JNZ rel32 D Valid Valid Jump near if not zero (ZF=0). 0F 80 cw JO rel16 D N.S. Valid Jump near if overflow (OF=1). Not supported in 64-bit mode. 0F 80 cd JO rel32 D Valid Valid Jump near if overflow (OF=1). 0F 8A cw JP rel16 D N.S. Valid Jump near if parity (PF=1). Not supported in 64-bit mode. 0F 8A cd JP rel32 D Valid Valid Jump near if parity (PF=1). 0F 8A cw JPE rel16 D N.S. Valid Jump near if parity even (PF=1). Not supported in 64-bit mode. 0F 8A cd JPE rel32 D Valid Valid Jump near if parity even (PF=1). 0F 8B cw JPO rel16 D N.S. Valid Jump near if parity odd (PF=0). Not supported in 64-bit mode. 0F 8B cd JPO rel32 D Valid Valid Jump near if parity odd (PF=0). 0F 88 cw JS rel16 D N.S. Valid Jump near if sign (SF=1). Not supported in 64-bit mode. 0F 88 cd JS rel32 D Valid Valid Jump near if sign (SF=1). 0F 84 cw JZ rel16 D N.S. Valid Jump near if 0 (ZF=1). Not supported in 64-bit mode. 0F 84 cd JZ rel32 D Valid Valid Jump near if 0 (ZF=1).
--jeroen
The Wiert Corner - irregular stream of stuff 