Re: [avr-llvm-devel] Toolchain support needed!

[Weddington, E. <Eri...@at...>]

Hi Borja,

I'm looking into it as we speak...

However, I will also be traveling to the Maker Faire New York this week. I think I'll have some extra "off-time" for this effort...

Eric

> -----Original Message-----
> From: Borja Ferrer [mailto:bor...@gm...]
> Sent: Saturday, September 22, 2012 10:05 AM
> To: Weddington, Eric
> Cc: avr...@li...
> Subject: Re: [avr-llvm-devel] Toolchain support needed!
> 
> ping
> 
> 
> 2012/9/9 Borja Ferrer <bor...@gm...>
> 
> 
> 	Hi Eric, welcome back!
> 
> 	Basically the situation is what I wrote in my previous email. We need
> to get a very basic toolchain working so we can complete the path from the
> .c to a .hex file. The backend should be able to compile any C code by now,
> except for new bugs and inline asm. If we're able to compile larger
> projects with the toolchain then we'll be able to detect more bugs and get
> a more reliable backend faster.
> 
> 	Currently, clang+llc (llc is the program that does the LLVM IR to AVR
> asm conversion) is able to compile C code to .S text asm files. The missing
> steps have to be done by avr-gcc, this is: generating the object files,
> linking them and generating hex files.
> 	My current setup is (under linux): an avr-gcc+avr-libc installation
> as described in the avr-libc manual, and a llvm installation, both in
> separate folders.
> 
> 	If you run this cmd line: clang -O3 test.c -o test.o -ccc-host-triple
> avr-generic-generic -ccc-gcc-name avr-gcc -mmcu=avr5
> 	clang drives llc to generate the .S file, then with the -ccc-gcc-name
> avr-gcc param it calls avr-gcc passing that new generated .S file so it can
> be converted to an object file with the help of the mmcu param indicating
> for what mcu we're compiling.
> 	avr-gcc has some logic inside where to drive the assembler and linker
> depending on the mmcu param it will call the linker with different options,
> for example the crt files involved. This is why for now we need avr-gcc,
> it's used as a driver for the linker and the assembler. Of course in the
> future we should be able to generate .o ELF files and an integrated
> assembler with llvm, but that will come later when we have a more mature
> backend.
> 
> 	One important thing is that clang has to use avr-libc's include files
> not the system's defaults, now when I include stdio.h it's using the linux
> header file, not the avr specific one. So obviously this has to be fixed,
> but we need to know first where these files are going to be placed in our
> toolchain, i guess as a quick hack using the -I param could do it, but in
> avr-gcc nobody uses it, so we shouldn't add more complexity to the cmd
> line.
> 
> 	If you need any other details, explanation or something I missed out
> let me know.
> 
> 
> 	2012/9/7 Weddington, Eric <Eri...@at...>
> 
> 
> 		Hi Borja!
> 
> 		Sorry to respond late to this email...
> 
> 		This is really exciting!
> 
> 		You said you need help in getting a basic toolchain working.
> Help me understand in detail, what you have, and where you want to be.
> 
> 		We need avr-gcc to run the assembler and linker. From avr-llvm,
> we have a compiler that will compile C to assembler. I would think that we
> would need to modify the avr-gcc specs to call the correct (new) executable
> for the compilation step.
> 
> 		If you can give me a few more details on your setup, then let's
> see where we can go with it. :-)
> 
> 		Eric
> 
> 
> 		> -----Original Message-----
> 		> From: Borja Ferrer [mailto:bor...@gm...]
> 		> Sent: Tuesday, August 28, 2012 4:24 PM
> 		> To: avr...@li...
> 		> Subject: [avr-llvm-devel] Toolchain support needed!
> 		>
> 		> 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!
> 
> 
> 
>