Compilling with float?

Posted on May 17, 2011 at 12:36

Hello,

In my project I must use float numbers, but on compiling I become this error:

undefined reference to `__aeabi_ui2f'

undefined reference to `__aeabi_fdiv'

I start the linker with this command:

arm-none-eabi-ld -v -lgcc -LC:/WinARM/CodeSourcery/lib/gcc/arm-none-eabi/4.2.3/thumb -Tprj/STM32F103CB-ROM.ld -Map=main.map out/lib/src/cortexm3_macro.o out/src/main.o out/src/stm32f10x_it.o out/src/stm32f10x_vector.o out/src/analogout.o --output main.elf

The path from parameter -L exists, the file libgcc.a, too.

Or have I forgot a parameter?

Thank you for help. Regards Markus.

Posted on May 17, 2011 at 12:36

Quote:

In my project I must use float numbers,

Must you?

Why?

In very many cases, integers or fixed-point are preferable - especially if you can't get the floating-point to work! 8-)

Posted on May 17, 2011 at 12:36

yes but if you use gcc to link then you will not have a issue.

I have never understand why people call ld directly.

Cheers

sjo

Posted on May 17, 2011 at 12:36

In a other forum have one person write me the right solution:

''Häng das -lgcc mal hinter die Liste von *.o Files.''

Posted on May 17, 2011 at 12:36

Try calling the linker using the gcc driver, it will probably solve your problem, eg.

arm-none-eabi-gcc -Wl,-LC:/WinARM/CodeSourcery/lib/gcc/arm-none-eabi/4.2.3/thumb -Tprj/STM32F103CB-ROM.ld,-Map=main.map out/lib/src/cortexm3_macro.o out/src/main.o out/src/stm32f10x_it.o out/src/stm32f10x_vector.o out/src/analogout.o -o main.elf

Cheers

sjo

[ This message was edited by: sjo on 10-06-2008 15:08 ]

Posted on May 17, 2011 at 12:36

Yes, the arm-none-eabi-gcc can linking, too, and it is working.

Thank you for help.

Posted on May 17, 2011 at 12:36

Hi all,

I've used Both Keil version 3.22 ( Free version 32K) and IAR EWARM v5.11 ( Free version 32K) , not yet GCC from CodeSourcery on a small routine using ''cos(), sin(), one addition , one multiplication and one division with only ''float'' variables using Keil ''MCBSTM32'' board at 8Mhz and I found that the same function is 7 time faster with IAR than using Keil floating librairies.

I' very intersted to see the result with GCC :) and I'm wondering if you have experienced similar results ? which seems very strange and keil is not providing optimized floating libraries.

Best Regards,

Asterix.

Ps: I've used #include ''math.h'' in the header files.

[ This message was edited by: asterix.magigimix on 10-06-2008 17:47 ]

Posted on May 17, 2011 at 12:36

Hi sjo, Asterix,

I've done some basic measurements with RVCT ( Keil 3.22) and EWARM 5.11 from IAR using our Cortex-M3 and here is my function :

#include

#define __pi 3.14159265

float var1 = __pi ;

float var2 = __pi/2;

float var0[10] = {0,0,0,0,0,0,0,0,0,0};

int main(void)

{

var0[0]= cos(var1);

var0[1]= sin(var1);

var0[2]= sqrt(var1);

var0[3]= atan(var1);

var0[4]= var2 + var1;

var0[5]= var2 * var1;

var0[6]= var2 / var1;

while(1);

}

Results are :

Cortex-M3, Keil 3.22 compiler 32 bit floats,exact CPU cycles

cos 41359

sin 43389

sqrt 3090

atan 42243

add 127

mul 624

div 445

Cortex-M3, IAR 5.11 compiler 32 bit floats,exact CPU cycles

cos 1864

sin 1946

sqrt 2725

atan 3423

add 40

mul 33

div 53

I'm quite surprised too by the results, where I see that keil is completely off while using trigonometric libraries. May be I'm missing something here ? Could you please try the same at your end and tell me your results for GCC from codesourcery.

Cheers,

STOne-32.

Posted on May 17, 2011 at 12:36

that quite old version of the arm gcc compiler.

i would check with a newer arm-eabi compiler, floating point performance is supposed to have improved quite a bit over the older arm-elf compiler.

Cheers

sjo