[avr-llvm-devel] Toolchain support needed!

[Borja F. <bor...@gm...>]

Hello,

With the latest changes, the backend is reaching the point where it can
compile nearly any sort of code. One thing that is missing is support for
inline asm which is heavily used in avr-libc, but apart from that it should
be able to compile the rest. With a few tweaks i've been able to compile a
2200 line C file that stresses floating point calculations that produces
around 22k instructions (C file -> S file)

Now I'm getting more interested on getting a very basic toolchain working,
Eric we'll need your help here. I've been able to build from a C file to a
hex file a very basic main() function. avr-gcc is needed to produce the elf
files and to drive the linker, so we'll have to stick with it for a while.
The setup I have is messy because avr-gcc is in one folder with avr-libc
and clang and llvm in another, so in order to get the toolchain with a
decent setup both things should be in the same folder. Also included files
default to the system's not the avr specific ones. Maybe others have tried
it before, so i want to know how you did it or how hard it was, but in my
case my first try was yesterday.

Also I'm going to change how register-pairs are represented because avr-as
can't understand what r29:r28 is. The llvm asm writer needs a bit of
tweaking because avr-as can't understand some asm directives it produces.

This is the cmd line i'm using to generate an object file: clang -O3 test.c
-o test.o -ccc-host-triple avr-generic-generic -ccc-gcc-name avr-gcc
-mmcu=avr5
notice that avr-gcc is passed so that clang can drive it once the .S file
is generated.

So try compiling a trivial main function to get the hex file generated,
you'll need avr-copy (provided by binutils) to convert the elf file to hex,
but that is easily handled by makefiles. Also people using windows try
doing it aswell since I dont have a setup for it and I'm looking forward
for it.

Once we get the basic toolchain working, adding support for avr-libc and
linking programs with its libraries should be much easier. I look forward
for any help here!