Embedded ARM assembly compile error on STm32F4

[CCont.1]

Hello,

I'm working on a library for nucleo F401RE board, with LL library, I'm trying to add some embedded ARM assembly code as written in the guide of arm Developer web site:

__asm return-type function-name(parameter-list)
{    
  // ARM/Thumb/Thumb-2 assembler code
  instruction{;comment is optional} 
  ... 
  instruction
}

My function is :

__ASM uint8_t ARM_GET_pin(PIN_TypeDef *pin_number) {
 
	// ARM instructions 
	
}

I'm using "__ASM" instead of "__asm" just beacuse it is defined in the files "cmsis_***.h",

I write the function, but when I build the code I get the following error:

../Core/Inc/stm32f4_REGISTER_instruction.h:102:7: error: expected '(' before 'uint8_t'
  102 | __ASM uint8_t ARM_GET_pin(PIN_TypeDef *pin_number) {
      |       ^~~~~~~
      |       (

I have tryed to change the return-type, as well as the function arguments, or add a "( )" that contains all the code __ASM(function), but it doesn't work.

There is a way to use embedded ARM with STM32CubeIDE?

Thanks in advance.

[TDK]

You can't just add __ASM to a C function to make it into assembly code. Here is an example of a function which uses assembly within it:

/**
  \brief   Reverse bit order of value
  \details Reverses the bit order of the given value.
  \param [in]    value  Value to reverse
  \return               Reversed value
 */
__attribute__((always_inline)) __STATIC_INLINE uint32_t __RBIT(uint32_t value)
{
  uint32_t result;
   __ASM volatile ("rbit %0, %1" : "=r" (result) : "r" (value) );
  return(result);
}

[Tesla DeLorean]

Consider that GNU's syntax is different from ARM/KEIL

Look for other examples within the CMSIS include/source files as those will likely contain both forms.

[CCont.1]

I see thank you,

just a question, as far as I know this looks to me as "inline assembler" and it is optimized by the compiler with the C code right?

While in "embedded assmbler" it is assembled separately from the C code, or they are the same in term of code optimization?

[TDK]

This is inline assembly code, yes. If your entire file is in assembly, you can just write it using assembly language. For example, the startup_*.s files generated by CubeMX are assembly. But assembly language has no concept of a C identifier such as "uint8_t" or "PIN_TypeDef".

As far as optimization, for inline assembly, the compiler won't touch the assembly code, but it will try to optimize the C-specific features within the file.