Re: mixing C and assembly

Neil wrote:
Walter Banks wrote:

Neil wrote:

Walter Banks wrote:
Vladimir Vassilevsky wrote:

You have to resort to assembly in the two special cases:

1. The system level work like switching the contexts of the tasks, C
startup code, etc.

2. The parts of code where the performance is very critical.
In your second point I would qualify it to parts of code
requiring exact timing on anything that we have released
recently that seems to be the only limitation.


Do not forget the startup code

Our startup code is in C.

w..



I am not sure how that works. I am talking about the code that jumps to main after setting up the C environment.

So is he.

There are small bits of the startup that must be in assembler (I use embedded assembly within the C code - Walter uses C extensions in his compilers that translate directly to matching assembly). But most of it can be written perfectly well in C. For example, code to copy the initialised data from flash to ram, and to zero the bss, can be written in C.
.

Relevant Pages

  • Re: mixing C and assembly
    ... The system level work like switching the contexts of the tasks, ... startup code, etc. ...
    (comp.arch.embedded)
  • Re: Startup code
    ... In my opinion, startup code is code executed from the reset of the CPU, ... things that need to be done before the main part of a program can run - setting up critical hardware, setting up the stack, clearing out bss, copying initial data segments, copying program data from flash to ram, calling C++ constructors, starting main, initializing other hardware and software. ... Code for setting up the stack, clearing bss, and copying the initial data segment is generally part of the "crt0" module that comes with your C compiler. ... It's frequently written in assembler, ...
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  • Re: mixing C and assembly
    ... The system level work like switching the contexts of the tasks, ... Do not forget the startup code ...
    (comp.arch.embedded)
  • Re: mixing C and assembly
    ... The system level work like switching the contexts of the tasks, ... Do not forget the startup code ... There are small bits of the startup that must be in assembler (I use ... I've written the startup code in C on the SDCC compiler and the small ...
    (comp.arch.embedded)
  • Re: Startup code
    ... >In my opinion, startup code is code executed from the reset of the CPU, ... >> The compiler vendor will not typically know how the processor ... >Again, all startup codes I have seen so far, were written in assembler. ... there is no environment set up yet to run ...
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