What does JL mean in at&t syntax?

Question

I'm working on a project for school and I cannot find anything on the what JL means in at&t syntax. For reference, the question is to find the value of %eax when NOP runs. Here is the code it's used in:

MOV $492,%ebx
MOV $2494,%eax
MOV $28063,%ecx
CMP %eax,%ebx
JL L1
JMP L2
L1:
IMUL %eax,%ebx
ADD %eax,%ebx
MOV %ebx,%eax
SUB %ecx,%eax
JMP L3
L2:
IMUL %eax,%ebx
SUB %eax,%ebx
MOV %ebx,%eax
ADD %ecx,%eax
L3:
NOP

Also I would appreciate what JMP does as well as how the addition/subtraction/multiplication works (ADD/SUB/IMUL). I don't want to cheat, I just want to understand what's happening. For example, do you change the first number or the second when using math? Thank you all so much for helping.

Jump if Less than? It's not so much the AT&T syntax here as the x86 instruction set. — Andon M. Coleman, Nov 17 '14 at 21:34
@AndonM.Coleman: AT&T syntax does matter, because the operands are switched in AT&T syntax! — Pedro, Dec 06 '17 at 09:39

score 12 · Answer 1 · answered Jul 26 '17 at 13:22

Unfortunately, I can't comment due to low reputation. However, the above answers are not fully correct.

The information that the code is given in AT&T syntax is crucial to give the correct answer, since the operands are switched in AT&T syntax. In fact, what the code

CMP %eax,%ebx
JL L1

interpreted in AT&T syntax does is: "If the contents of EBX are less than the contents of EAX, jump to the label L1" - and not the other way round as mentioned before.

score 2 · Answer 2 · answered Nov 17 '14 at 21:34

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jl (jump on less than, signed) wiki

answered Nov 17 '14 at 21:34

incogn1to

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score -1 · Accepted Answer · edited May 23 '17 at 12:25

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That is assemply language , JL is Jump if Less

This also works in x86 assembly language.

 CMP %eax,%ebx 
 JL L1

We compare EAX to EBX, then we'll jump to L1 depending on that comparison.

More specific - If the contents of EAX are less than the contents of EBX, jump to the label L1

See - Assembly - JG/JNLE/JL/JNGE after CMP

edited May 23 '17 at 12:25

Community

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answered Nov 17 '14 at 21:34

Caffeinated

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That makes sense, but how does it jump is %eax is more or if %ebx is more? – Ella Nov 17 '14 at 21:40
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Will it jump to L1 if %eax is more or if %ebx is more? – Ella Nov 17 '14 at 21:41
@Ella - we say "less than the contents of EBX," means , EBX right ? – Caffeinated Nov 17 '14 at 21:46
@Ella - It's been a while for me, since I touched ASM – Caffeinated Nov 17 '14 at 21:46
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@Coffee: Now that I have enough reputation to write a comment: Could you please correct your sentence "More specific - If the contents of EAX are less than the contents of EBX, jump to the label L1"? In AT&T syntax it is exactly the other way round, and OP explicitly asked for AT&T syntax. See my answer to this question. – Pedro Dec 06 '17 at 09:38

What does JL mean in at&t syntax?

3 Answers3

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