Can the compiler push almost all registers for linear assembly usage?

Robert W

Hi,

I want to write a linear assembly function. In order to improve performance, I hope to use more registers in the linear assembly function, which is called from C program. On the C ompiler optimization manual, it says that some registers are used by the parent C program. In C64xx DSP, there are 64 32-bit registers. Can I use near 64, (if not all 64, such as 58, 60 registers) in the linear assembly function?

over 12 years ago

0 Archaeologist over 12 years ago

TI__Guru* 84285 points

You can use all of them but SP(B15) and DP(B14), which you should leave alone. If you disable interrupts, you can even use those, but you'll have to save/restore them yourself.

You could just use symbolic registers and let the compiler take care of register allocation for you.

0 Robert W over 12 years ago in reply to Archaeologist

Mastermind 7100 points

Hi,

I get a new question after you answered my original post.

Does the compiler save the AMR register for the linear assembly function?

I notice that a linear assembly function on the e2e forum using:

MVC AMR, AMRreg ;save AMR reg.

iloop: .trip 3
[count] B oloop
end: MVC AMRreg, AMR ;restore AMR reg
.endproc

These AMR save and restore are not necessary?

Thanks,

0 Archaeologist over 12 years ago in reply to Robert W

TI__Guru* 84285 points

When I said "all of them" I meant A0-31 and B0-31. See the C6000 Optimizing C/C++ Compiler User's Guide (SPRU187) for information about which registers the compiler saves and restores automatically. http://www.ti.com/lit/ug/spru187u/spru187u.pdf

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Can the compiler push almost all registers for linear assembly usage?