MikroBasic Efficency

[Alessandro Fulignani]

Dear MikroE,

I am working on a firmware that require an intensive use of square roots.
So i decided to use an stm32 with floating point. Then i have started to look at the efficency, because of the slow response of the application.

Here my question:

I have included in the project the library "Q31".

Then i did this simple test:

Basic (or C)
-------------
A1=9
A=sqrt(A1)
-------------

ASSEMBLER

------------------------
asm
VMOV.F32 S1,#9
VSQRT.F32 s1,s2
end asm
------------------------

Here the lister output for the assembly written code:

VMOV.F32 S1, #9
VSQRT.F32 S1, S2

Execution time @1Mhz

VMOV.F32 S1, #9 ---> 1uS (1 Cycle)
VSQRT.F32 S1,S2 ----> 14uS (14 Cycles)

Here the lister output for the Basic( or C ) written code:

VMOV.F32 S0, #9 ---> 1uS (1 Cycle)
BL _sqrt+0 -------> 369 uS ( 369 Cycles)

If you analyze the listing output of the routine (_sqrt+0) you will see an indirect calculation of the square root instead of the use of the OP-code implemented in the FPU!!

Is it a bug?

Let me know,

Alessandro

[filip]

Hi,

Which MCU are you using ?

Regards,
Filip.

[Alessandro Fulignani]

Hi Filip,

I am working MikroBasic 5.1.0 on Windows 10.

And i am doing this test switching between a STM32F071V8 and a STM32L476VE/STM32F401VB.

Basically, i am switching between an M0 and an M4.

Here another example:

------------
Basic (or C)
------------

dim A1,A2 as float

A1=A1*A2

Totally 11 Cycles

The compiled output use the VMUL.F32 OP-Code.

-----------
Assembler:
-----------

asm

VMOV.F32 S2,#1.5
VMOV.F32 S1,#1.5
VMUL.F32 S2,S1

end asm

Totally 3 Cycles

----------------------------------------

I got same good results with VDIV.F32 VADD.F32 VCMP.F32 VCMPE.F32

Here there is a good efficency.

In the Basic program used as test, is included the transfer between the CPU and FPU, so the assembler implementation seems to be good.

I am looking at some other inconsistencies...i will report them in the next days.

Thank you very much for your help!

Alessandro

[filip]

Hi,

Thank you for this explanation, I will pass it to our developers.

Regards,
Filip.