Nekonomicon - if U were a RISC assembly programmer which instructions would U want to have ?

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 2, 2016, 12:01 p.m...

I am going to improve the above design (soft core, fpga): suggestions, tips, are the welcome

BP stands for "break point"
WP stands for "watch point"
EA stands for "effective address" (physical address)

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 3, 2016, 1:16 a.m...

I was thinking about the following instruction (from PowerPC):

Code: Select all


isel rdest, ra, rb, rsel

if rsel isEqualTo 0 then rdest gets the value of ra
if rsel isNotEqualTo 0 then rdest gets the value of rb

I got the following advice:

HCF. Halt and Catch Fire. The only instruction you need

from IBM S/360 :lol:

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

ClassicHasClass
Donor
From Sunny So Cal
Who joined July 25, 2012, 7:12 p.m.

Wrote the following at March 3, 2016, 8:04 a.m...

I use fsel a lot. I was surprised isel was not in Power Macs.

smit happens.

:Fuel:

bigred , 900MHz R16K, 4GB RAM, V12 DCD, 6.5.30
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indy , 150MHz R4400SC, 256MB RAM, XL24, 6.5.10
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probably posted from

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commodorejohn
Who joined Oct. 2, 2012, 1:22 p.m.

Wrote the following at March 3, 2016, 8:53 a.m...

Haha, they made an instruction specifically to implement the ternary operator

Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
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guardian452
Donor
From Kentucky, United States
Who joined Aug. 21, 2007, 10:12 p.m.

Wrote the following at March 3, 2016, 12:52 p.m...

An instruction that reads a a string and automatically convers " u " to " you " :lol:

Google: Don't Be Evil. Apple: Don't Be Greedy. Microsoft: Don't Be Stupid.

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 3, 2016, 1:59 p.m...

guardian452 wrote: automatically convers " u " to " you "

I was worried that the title was too long, so I contracted

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 14, 2016, 5:41 a.m...

Progress

I have confirmed the following classes & instructions:

Class.Alu.Logic
and
nand
or
nor
xor
xnor
Shift.R
Shift.L

Class.Alu.Arithmetic
Add.signed
Add.unsigned
Sub.signed
Sub.unsigned
Mul.signed
Mul.unsigned
Div.signed
Div.unsigned

Class.Alu.Bitfield
Bit.get
Bit.set
Bit.toggle
Bit.get.first
Bit.set.first
Bit.rotate
Bit.sign-extend
Bit.swap

Class.IO
Load.8
Load.16
Load.32
Store.8
Store.16
Store.32

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

robespierre
From Boston
Who joined Sept. 12, 2011, 2:28 p.m.

Wrote the following at March 14, 2016, 9:14 a.m...

Only one kind of right shift?

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 14, 2016, 10:27 a.m...

yes, it's the easiest shift-right I can implement, and it takes 1 cpu cycle to complete
but I have 2 empty classes, so, I can add more instructions (and ALU modules)
suggestions

?

do I have to implement Circular Shift units ?

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

robespierre
From Boston
Who joined Sept. 12, 2011, 2:28 p.m.

Wrote the following at March 14, 2016, 11:58 a.m...

I thought you already had that covered with "bit.rotate", but maybe I didn't grasp the intent.
I mean that if you only have one type of right shift, it can't accommodate both logical and arithmetic forms.

Code: Select all


unsigned r1=0xF0F0F0F0;


r1>>=4; // srl r1,r1,#4


assert(r1==0x0F0F0F0F);

vs

Code: Select all


signed r1=-16;


r1>>=4; // sra r1,r1,#4


assert(r1==-1);

P.S. it can also be useful to have "arithmetic left shift" depending on how condition codes and traps are architected. If you can always test overflow after a shift you don't need it.
The other approach is to have "arithmetic shift" and "logical shift" opcodes with a signed (or excess represented, because you don't want to waste a bit for zero) distance. Depending on addressing modes this can allow for both immediate or register distance operand.

robespierre
From Boston
Who joined Sept. 12, 2011, 2:28 p.m.

Wrote the following at March 14, 2016, 12:21 p.m...

POWER has very good shift instructions, with rlwmi you can implement multi-precision shifts in a tight loop.

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 16, 2016, 6:43 a.m...

Unfortunately I do not have books about the POWER architecture, and I do not have yatta materials about Power/PC, not in details

I have to take a decision about the branch-instructions

the 68K way : do ALU, which modifies the condition code register, then test CCR.bit, in case it matches then branch
the 88K way : compare and set a register with results (equal? greater? zero? ….), then get-bit, and if it's "1" than branch
the MIPS way : compare and branch (1 instruction)
the ARM60 way : similar to m68k, it adds 4 bit as " conditional execution ", an instruction is executed if these 4 bits match the CCR status

Ironically, I can implement all of these branch-methods

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 18, 2016, 4:31 a.m...

I confirm the following branch & trap instructions:

ConditionalExecution.Branch.if.bit.set
ConditionalExecution.Branch.if.bit.clr
ConditionalExecution.Trap.if.bit.set
ConditionalExecution.Trap.if.bit.clr

as you can access r0 which always return zero (0x0000.0000)
the following instructions are a subset case of the above

ConditionalExecution.Branch
ConditionalExecution.Trap

e.g.
ConditionalExecution.Branch is implemented as ConditionalExecution.Branch.if.bit.clr using r0
is bit.whatever clear in r0 ? yes, always

Conditional Execution uses 16 conditions (4 bit, encoded, including overflow, carry, zero, negative, positive, etc) from the CCR (conditional code register)
you can choose to " inhibit " the updating of the CCR, each instruction features the choice as there is a specific " CCR inhibit " bit in the Instruction forma (above is called " mode ", I still have to rename it in the documentation)

each branch can be specified as

PC=rs1
PC=imm32
PC=rs1+signed(imm32)

which permits absolutes branches, and relative branches, and register-driven branches
(the program counter is now part of the registers-set, rs1 can be equal to PC)

what do you think ?

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

ivelegacy
From Italy
Who joined Jan. 4, 2015, 5:12 a.m.

Wrote the following at March 19, 2016, 11:32 a.m...

I am also going to add

saturated arithmetic
test r0: { branch if zero, otherwise decrement by 1 } (it's used in 68k)

I wish I could enter into the vegetable garden of William Gibson , on the right of a director, to decide how a film is ultimately released for public viewing, but I am not a nor Cyberpunk writer neither a dude in Hollywood , and my English still looks like an old rusty trailer which needs a fix-up, so my personal wonderland begins with a pill ... tumbling down the rabbit hole , where the sky above the router port is the color of television, tuned to a dead channel and some gears still need a debugger there.

vishnu
Donor
From Minneapolis, Minnesota USA
Who joined March 18, 2007, 3:25 p.m.

Wrote the following at March 22, 2016, 12:34 p.m...

Don't forget "Halt and Catch Fire," obvious, I know, but someone had to say it... :lol:

Project:
Temporarily lost at sea...
Plan:
World domination! Or something...
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Everything Else

if U were a RISC assembly programmer which instructions would U want to have ?