Assembly Mnemonics You Didn't Know About

ben_lubar

Inspired by https://twitter.com/ppcinstructions

SRFZPCVZ - subtract register from zero permanently changing value of zero

LEAES - load effective address of egg salad

DIBZ - divide immediate by zero

JBO - switch processor to lojban mode

jo'au - change version of lojban parser

JEFF - jump if string equal to "Firefox"

JLIQBOR - jump if user is dumber than a box of rocks

Zecc

VHJ - Jump. You might as well jump.

dkf

SMLSLD — I want a Small Salad

Applied Mediocrity

A couple from x86-64 ARS-NI (Advanced, but Rather Silly New Instructions)

TESTNFA - test if not Friday afternoon
FISTP - congratulate yourself on a job well done
LOOPNZ - loop around New Zealand
MOVNO - unconditional "don't move"
MBYMOV - randomly reorganize the department
YNOTXCHG - exchange in a devil-may-care fashion
CVE - execute the specified Intel vulnerability number
PORQUE - Manuel bitwise logical OR
NIKE - just do it

And, of course:

WTFENTER
WTFEXIT

_{Edit: bug fixes and speedy performance improvements}

Onyx

@Applied-Mediocrity said in Assembly Mnemonics You Didn't Know About:

TESTNFA - test if not Friday afternoon

You jest, but... https://wiki.asterisk.org/wiki/display/AST/Application_GotoIfTime

@Applied-Mediocrity said in Assembly Mnemonics You Didn't Know About:

And, of course:

WTFENTER
WTFEXIT

WTFFNF

Cursorkeys

TESTC - Sets flag if your coffee has gone cold while writing this code
JA - Jump anywhere; surprise me
PC - Disables all bus masters

dkf

@Cursorkeys said in Assembly Mnemonics You Didn't Know About:

PC - Disables all bus masters

It just renames them to “bus collaboration colleagues”.

Zecc

JOCTRSFRGR - Jump over the counter and steal from the register

heterodox

Obligatory:
HCF – Halt and Catch Fire

mott555

@heterodox said in Assembly Mnemonics You Didn't Know About:

Obligatory:
HCF – Halt and Catch Fire

No, that one expands the processor to fill a volume of a hundred cubic feet.

xaade

@Applied-Mediocrity said in Assembly Mnemonics You Didn't Know About:

NIKE

Sacrifice everything and melt the processor.

cvi

@Applied-Mediocrity said in Assembly Mnemonics You Didn't Know About:

NIKE - just do it

That's a prefix that you can apply to certain instructions (like LOCK), right?

anotherusername

@ben_lubar said in Assembly Mnemonics You Didn't Know About:

JEFF - jump if string equal to "Firefox"

No, that can't possibly be right.

anotherusername

@mott555 said in Assembly Mnemonics You Didn't Know About:

@heterodox said in Assembly Mnemonics You Didn't Know About:

Obligatory:
HCF – Halt and Catch Fire

No, that one expands the processor to fill a volume of a hundred cubic feet.

So, more like an explosion than a fire?

Applied Mediocrity

@xaade, @cvi
That is correct. For this purpose in our 10th generation Vapor Lake processors TIM has been replaced with scented paraffin wax.

dkf

@ben_lubar said in Assembly Mnemonics You Didn't Know About:

JEFF - jump if string equal to "Firefox"

Surely that's the instruction for telling code that it is no longer welcome here?

anotherusername

@dkf said in Assembly Mnemonics You Didn't Know About:

@ben_lubar said in Assembly Mnemonics You Didn't Know About:

JEFF - jump if string equal to "Firefox"

Surely that's the instruction for telling code that it is no longer welcome here?

JEFF - Deletes the contents of random registers. Reason: no longer welcome here.

May also kill or fork the active thread for no apparent reason.

Placeholder

JLPT - Randomly flip some less significant bits of the program counter register every few instructions for the next several seconds.

HardwareGeek

@Placeholder said in Assembly Mnemonics You Didn't Know About:

Randomly flip some less significant bits

Eh, if you're going to do it, do it big; flip the most significant bits. Because it's more significant!

lolwhat

@Applied-Mediocrity said in Assembly Mnemonics You Didn't Know About:

PORQUE

https://uproxx.files.wordpress.com/2016/12/yakskrt-jpg.jpeg

Placeholder

@HardwareGeek said in Assembly Mnemonics You Didn't Know About:

@Placeholder said in Assembly Mnemonics You Didn't Know About:

Randomly flip some less significant bits

Eh, if you're going to do it, do it big; flip the most significant bits. Because it's more significant!

Significance doesn't matter: it's how you use it!

pie_flavor

FJCVTZS - Floating-point Javascript ConVerT to Signed fixed-point, rounding toward Zero.
Wouldn't it be hilarious if there was actually bare-metal support for a JS insanity?
Oh wait, there is.

cvi

@pie_flavor

Why does that instruction talk about fixed-point? If I read it correctly, it just converts the source floating point number to a 32-bit signed integer, rounding to zero. (FCVTZS already does that, but with a bit more options, including the possibility for actual fixed-point conversions.)

Jaloopa

@anotherusername said in Assembly Mnemonics You Didn't Know About:

@ben_lubar said in Assembly Mnemonics You Didn't Know About:

JEFF - jump if string equal to "Firefox"

No, that can't possibly be right.

JEFF - if on a mobile processor, do something different

topspin

@pie_flavor said in Assembly Mnemonics You Didn't Know About:

Wouldn't it be hilarious if there was actually bare-metal support for a JS insanity?

So much for RISC.

Jaloopa

SUBLEQ - subtract value 1 from value 2 and jump if less than or equal to zero.

Seriously, who needs anything else?

dkf

@cvi said in Assembly Mnemonics You Didn't Know About:

Why does that instruction talk about fixed-point?

It's used on platforms where there isn't much hardware for floating point, and where converting a true float into something that can be handled efficiently (some fixed point type, probably either s15.16 or s31.32; I'd need to look at the details to see which) is a big win. It's important for some embedded processors, and makes it much easier to efficiently execute javascript on them. Apparently there's at least one customer who really wanted that…

cvi

@dkf No, I get why you'd want fixed-point, but the instruction in question (FJCVTZS) just converts to a signed integer (32-bit):

Floating-point Javascript Convert to Signed fixed-point, rounding toward Zero. This instruction converts the double-precision floating-point value in the SIMD and FP source register to a 32-bit signed integer using the Round towards Zero rounding mode, and write the result to the general-purpose destination register. If the result is too large to be accomodated as a signed 32-bit integer, then the result is the integer modulo 232, as held in a 32-bit signed integer.

You need the general non-javascript version of the instruction to convert to fixed-point (and there you can select the format and also use a 64-bit destination).

TwelveBaud

TEST M: Set condition register if any other process, anywhere in the network, even if it's not actually connected to the network, is writing to the M register. Otherwise, clear condition register.

SWIZ r1 r2 r3: If r1 or r2 are pointers or if any digit of r2 is greater than 4, fault. Otherwise, set each digit of r3 to the $(corresponding digit of r2)th digit of r1.

PleegWat

@TwelveBaud Like in Shenzhen IO, in Exapunks they are telling us again that the future is BCD.

dkf

@TwelveBaud said in Assembly Mnemonics You Didn't Know About:

SWIZ r1 r2 r3: If r1 or r2 are pointers or if any digit of r2 is greater than 4, fault. Otherwise, set each digit of r3 to the $(corresponding digit of r2)th digit of r1.

“Hey, there's some opcodes there (for SWIZ with indirect arguments) that can be repurposed to be a different instruction! That'd be great for generating a trap to kernel mode…”

… which is exactly how far too many hardware designers work. Saving a bit here, chiselling a few gates there, and turning all software built on top into a festering horror. It sounds like an exaggeration, but I've seen it happen multiple times. (I'm still aggrieved that the hardware designers for our next-gen chip thought it was a good idea to have operating modes where memory accesses would sometimes just vanish entirely. Because… Fuck You No! Give us a fucking data abort perhaps, but never make a memory access just vanish as we'll for sure never hunt down those bugs! We don't care if it makes your hardware more complicated.)

TwelveBaud

@dkf The Exapunks ISA doesn't support alternate addressing modes; registers can hold either integers (-9999 through +9999, one zero, saturating arithmetic) or "keywords" (string-like symbols that cannot be expressed as literals), and for the purposes of this thread, I chose to interpret "keyword" as "pointer to memory that we cannot see that contains that symbol". Trying to use a register or pseudoregister that holds a keyword in an arithmetic context is a fatal error that terminates your EXA on the subsequent tick.

I completely agree with you regarding the illogical and potentially pathological work habits of hardware designers; I'm just providing context for my post.

PleegWat

@TwelveBaud IIRC, in that example, r2 can be either an immediate value or a register reference, and those are different addressing modes in hardware speak?

TwelveBaud

@PleegWat Fair point. It's technically
SWIZ N/R N/R R
which translates as
SWIZ imm1/r1 imm2/r2 r3
but

El_Heffe

@dkf said in Assembly Mnemonics You Didn't Know About:

SMLSLD — I want a Small Salad

And the corresponding YJHTGTBS - You Just HAD To Get The Big Salad