Hi,
After hearing Chris' talk at bossaconference I wanted to see if I could use LLVM (and/or
llvm-gcc) as a crosscompiler for ARM. The documentation beautifully outlines how to build
it for your host and how to crosscompile it, but not how to build it as a cross-compiler.
So my question is: How should I build llvm and llvm-gcc4 to have it cross-compile from x86
to ARM/EABI?
regards,
Koen
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Hash: SHA1Hi,
After hearing Chris' talk at bossaconference I wanted to see if I could use LLVM (and/or
llvm-gcc) as a crosscompiler for ARM. The documentation beautifully outlines how to build
it for your host and how to crosscompile it, but not how to build it as a cross-compiler.So my question is: How should I build llvm and llvm-gcc4 to have it cross-compile from x86
to ARM/EABI?
For the LLVM build, just build it on an x86 host and make sure the ARM
target is enabled. You can do that with the --enable-targets=ARM option
to configure. The default is to build all targets which will work fine
too.
For the llvm-gcc build, you just build it like you would any GCC
cross-compiler. That is, you use the --target option on the configure
line for llvm-gcc. The value of the --target option should be the target
triple that you want to cross compile too. I don't know the details but
it should be something like --target=arm-iphone-darwin.
This --target option in llvm-gcc will cause llvm-gcc to emit a
"target=arm-iphone-darwin" directive in the output to LLVM. This will
cause LLVM to select the ARM backend and any subtargets for
"iphone-darwin".
Please note, the "iphone-darwin" part is fictional. I don't know the
correct full target triple for your target but it at least starts with
"arm".
Reid.
Reid Spencer schreef:
Hi,
After hearing Chris' talk at bossaconference I wanted to see if I could use LLVM (and/or
llvm-gcc) as a crosscompiler for ARM. The documentation beautifully outlines how to build
it for your host and how to crosscompile it, but not how to build it as a cross-compiler.So my question is: How should I build llvm and llvm-gcc4 to have it cross-compile from x86
to ARM/EABI?For the LLVM build, just build it on an x86 host and make sure the ARM
target is enabled. You can do that with the --enable-targets=ARM option
to configure. The default is to build all targets which will work fine
too.
OK, that's easy I already have that working 
For the llvm-gcc build, you just build it like you would any GCC
cross-compiler. That is, you use the --target option on the configure
line for llvm-gcc. The value of the --target option should be the target
triple that you want to cross compile too. I don't know the details but
it should be something like --target=arm-iphone-darwin.
Is llvm-gcc4 a modified gcc? I have a big pile of patches to unbreak various part of gcc
4.1.x for ARM. E.g.
http://www.openembedded.org/repo/org.openembedded.dev/packages/gcc/gcc-4.1.2/unbreak-armv4t.patch
to make gcc stop emitting armv5te instructions for armv4t cpus. Will llvm-gcc4 require the
same patches.
This --target option in llvm-gcc will cause llvm-gcc to emit a
"target=arm-iphone-darwin" directive in the output to LLVM. This will
cause LLVM to select the ARM backend and any subtargets for
"iphone-darwin".Please note, the "iphone-darwin" part is fictional. I don't know the
correct full target triple for your target but it at least starts with
"arm".
'xscale' would also be an option, but lets not get into un(der)documented features in gcc 
It would probably be 'arm-<target vendor>-linuxgnueabi' for the things I'm interested in
(The neo1973 phone for example).
After having dealt with gcc as crosscompiler for the past years I get the "It can't be
this easy to setup" feeling, but I'll find out tomorrow.
Thanks for your speedy replies!
regards,
Koen