the call insctruction in c6000 assembly language

Hi Daniel,

At the time of compilation of a c program,

Wherever a C function is called in a c program, that function call will be replaced by its assembly instruction "call ".\

Say for example,

main()

----------

----------

Func();              it will be replaced by      call Func ;                          

---------

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For more information , check compiler user guide and assembler user guide for C6000 Devices.

http://www.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=spru187u

http://www.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=spru186w

I use the C6713 dsk.

Heres's the main file:
; logiciel code asm exploratoire
; Daniel Gaucher, 22 septembre 2015


.global func1 ; pas besoin de _ devant le nom de la fonction
.def _main ; le nom main semble obligatoire

.data
x .int 1,2,3
y .float 0.1, 0.2, 0.3



dec1 .macro A ; cd spru186w pour les macros
SUB A,1,A
.endm

.text

_main:

mvk 5, A5
call func1
nop 5
mvk 5, A3
dec1 A3



.end


the other asm file is:

.global func1


.data

.text

func1
.asmfunc

mvk 2, A2

.endasmfunc

.end

Daniel,

What does this generate for you in the output file? In other words, when you load it on the C6713 DSK and go to main at the start, then look in the Disassembler Window, what do you observe in that window for the 5 instructions you have written in main?

Do you find the CALL instruction listed in the instruction descriptions section of the TMS320C67x/C67x+ DSP CPU and Instruction Set Reference Guide? I do not find it there.

Why are you writing in assembly? This is very difficult to do, and very difficult for others to debug the large number of mistakes one can make when writing C6000 assembly.

The always right and best way to learn assembly is to write your program in C and look at the output of the C compiler. You can set flags in CCS so it will keep the .asm files it generates and also keep the listing .lst files which can have a lot of useful extra information.

With the C compiler, you can use different levels of optimization. For the first time you try it, do not use optimization so you can easily follow your program's flow. Then as you increase the optimization step-by-step, you can compare to see how the compiler has done things differently.

The bottom lines to your original query:

1. There is no 'call' instruction for the C6713.
2. There may be a 'call' macro used by some versions of the assembler or by some programmers who like it; in those cases you will need to locate that macro's definition somewhere, or do what I described above to see what the assembler generated for you.

Regards,
RandyP

Hi Randy

Thanks for your sound advices. As you may see, I'm not yet a pro in the field of C6000 assembly programming. However, thanks to you, I could figure out that the call word is synonymous to the b instruction. It does nothing less, nothing more than a simple branch to a symbol.  I just find curious that this substitution is not documented anywhere, yet it still works with compiler version 7.4.4 using ti's C6713 simulator (little endian).  I just can't trace back where I found the call instruction being used. Sure enough, I did not guess it.

Thanks again

Daniel

Daniel,

Is there some level of optimization on for the assembler? Even that would usually not affect what you have written in a .asm file but only in a .sa file.

In your source file, you would get the same code if you changed the CALL mnemonic to B, but a call is not the same as a branch. I do not know why it is behaving the way it is. You made some changes to your code which should have been put in by a CALL macro, but were not.

I will go back to my recommendation to write in C and learn from the assembly or listing output from the C compiler.

You are at a good starting point, but coding will be best for you in my opinion if you write in C and read assembly.

Regards,
RandyP

RandyP said:

In your source file, you would get the same code if you changed the CALL mnemonic to B, but a call is not the same as a branch. I do not know why it is behaving the way it is. You made some changes to your code which should have been put in by a CALL macro, but were not.

I don't understand what you're complaining about, RandyP. The confusion in this case is direct result of what you are preaching, i.e. "look at compiler output, you mortals." Compiler always uses 'call' in generated assembly listing which is not real instruction. Assembler does recognize it, just like it does a number of other "incorrect" mnemonics. It's not big deal.

RandyP said:

I will go back to my recommendation to write in C and learn from the assembly or listing output from the C compiler.

You are at a good starting point, but coding will be best for you in my opinion if you write in C and read assembly.

I once again want to point out that this just a personal opinion, and there are others. In the context I'd like to quote you, RandyP, from another thread: "I have tried for many years to understand programming the SPLOOP, and it escapes me." I'd say this is how your advice works. As already said earlier, by limiting yourself to compiler generated output you set boundary for learning, and from own experience I can tell that this boundary is actually low.

Andy POlyakov

I dislike very much the tone of your reply. Each of us has his own approach to complex problems. A litte respect is the primary sign of real professionalism.