Assembly syntax conversion from GCC to TI compiler

Searching in the forum i found that could be related to the fact that mnemonics start from column 1, which is reserved for labels. I also tried

asm(" mrc p14, 0, r0, c0, c0");

whithout success (same compiler output)

Thanks

Hi Archaeologist,

unfortunately your suggestion didn't work. 
If the architecture is the same, only changing compiler could cause differences in instruction syntax?
Thank you, 

The TI compiler does not support GNU-style inline assembly, and does not provide any way to refer to local variables from inline assembly.

Ok, is there any workaround I could use to achieve the same result?
Thank you 

Ok, probably the only workaround is to rewrite the complete function in assembly...here's the code:

int DCC_Read(UINT32 *read_data)
{
//assembler instructions to read data from coprocessor 14
//poll_rx:
// MRC p14,0,r0,c0,c0 @ read DCC control register
// TST r0,#1 @ read R bit
// BEQ poll_rx @ if R=0 branch to poll_rx
// MRC p14,0,r1,c1,c0 @ save data into r1
UINT32 read;

asm ("poll_rx:\n\tmrc p14,0,r1,c0,c0\n\ttst r1,#1\n\tbeq poll_rx\n\tmrc p14,0,%0,c1,c0\n\t"
:"=r" (read));
*read_data=read;
return (ANSW_OK);
}

Can I please have some help on how to rewrite this in assembly language?
Thank you, 

So that you can call the assembly function from C, make sure it adheres to the register conventions used by the compiler.  Please see the section titled Register Conventions in the ARM compiler manual.

Thanks and regards,

-George

Hi George,
thank you for this suggestion. I read the chapter and found some usefull information on how to do this rework. Here's how I modified my functions:

int DCC_Read(UINT32 *read_data)
{

//assembler instructions to read data from coprocessor 14
//poll_rx:
// MRC p14,0,r0,c0,c0 @ read DCC control register
// TST r0,#1 @ read R bit
// BEQ poll_rx @ if R=0 branch to poll_rx
// MRC p14,0,r1,c1,c0 @ save data into r1
UINT32 read;

read = poll_rx();

*read_data=read;
return (ANSW_OK);

}

int DCC_Write(UINT32 write_data)
{

/*assembler instructions to write data into coprocessor 14
poll_tx:
MRC p14,0,r0,c0,c0 @ read DCC control register
TST r0,#2 @ read W bit
BNE poll_tx @ if W=1 branch to poll_tx
MCR p14,0,r1,c1,c0 @ send data via DCC
*/

poll_tx(write_data);

return (ANSW_OK);

}

I added the two function definitions:

int poll_rx(void);
int poll_tx(unsigned long write_data);

I created a poll_rx.asm with the code below:

.global _poll_rx

_poll_rx:

MRC p14,#0,r1,c0,c0
TST r1,#1
BEQ _poll_rx
MRC p14,#0,r0,c1,c0

I changed the register assignment because return value must be on r0 register. I also created poll_tx.asm with the code below:

.global _poll_tx

_poll_tx:

MRC p14,#0,r1,c0,c0
TST r1,#2
BNE _poll_tx
MCR p14,#0,r0,c1,c0

I changed the register assignment because arguments are received starting from r0 on.

Can you please give me a review of this code and suggest me if can it work as expected?
Thank you very much,

You need some sort of return statement in each function to return to the caller

Hi Archaeologist,
you are right, in fact poll_tx works (being called last it doesn't matter the return statement), poll_rx instead has still some trouble. Reading example 6-1 of  ARM Optimizing C/C++ Compiler i found suggestion on how to create return statement. I tried to append:

MOV pc, lr

instruction at the bottom line of the two functions but it doesn't work. Should it be enough to return to the caller?
Thank you,

I'm not an ARM expert, but that doesn't seem quite right.  Try writing a similar function in C and examining the compiler's output assembly code to see what it does.  You can keep this file with the --keep_asm compiler option.

Thank you Cody,
this last tip did the work. Thank you all for your precious support,
Samuele