cross-compiling for arm with clang

[Damjan Marion]

On Jun 21, 2011, at 7:06 PM, Warner Losh wrote:
> 
> On Jun 21, 2011, at 3:12 AM, Damjan Marion wrote:
>> 
>> On Jun 17, 2011, at 9:16 PM, Warner Losh wrote:
>>> 
>>> How it normally works is that we build a compiler that invokes the right as, ld, etc for the architecture in question.  Clang is clearly broken here in assuming that as can cope with anything other than native assembler :)  We normally either build gcc that knows where to find these files.  In the buildworld case, this is communicate with weird paths and shell variables.  With the whole 'xdev' series of targets (which are instructive to look at), we build into a specific location /usr/freebsd-xdev-arm/bin, etc).
>>> 
>>> It works by accident for i386 on amd64, I think.  as treats the more or less as the same.
>> 
>> I submitted a patch[1] to clang mailer which invokes xxx-yyy-zzz-as/ld based on -ccc-host-triple. Patch is copy of netbsd code which is already in clang.
>> 
>> For me it works well, even when I use clang on Darwin host, it calls proper as/ld.
>> 
>> # /opt/llvm/bin/clang -ccc-host-triple arm-unknown-freebsd -mfloat-abi=soft  test.c -o test -v -c
>> clang version 3.0 (http://llvm.org/git/clang.git 98138cdfdee05c0afbab2b209ce8cfe4a52474e1)
>> Target: arm-unknown-freebsd
>> Thread model: posix
>> [snip]
>> End of search list.
>> "/opt/llvm/bin/arm-unknown-freebsd-as" -o test /var/folders/kb/kbDaYaFqFQaCg3mXbTLH5U+16gE/-Tmp-/cc-RMHOwf.s
>> 
>> 
>> Is this what we need to support cross-compiling freebsd with clang?
> 
> As we do it today?  No.  Today we build the binaries as 'as' which are part of the buildworld.  These binaries aren't called arm-unknown-freebsd-as, but instead 'as'.
> 
> Do we want to switch? Maybe.

Seems that clang will first try to run as/ld which is in the same directory like clang. That is exactly what we have in /usr/obj/.../bin so seems that buildworld should work out of the box.

Problem with ARM is that clang is not build as part of cross-tools, so clang from /usr/bin is called instead which also means that as/ld from /usr/bin are used.

--- share/mk/bsd.own.mk (revision 223366)
+++ share/mk/bsd.own.mk (working copy)
@@ -415,7 +415,7 @@
 __T=${MACHINE_ARCH}
 .endif
 # Clang is only for x86 and 32-bit powerpc right now, by default.
-.if ${__T} == "amd64" || ${__T} == "i386" || ${__T} == "powerpc"
+.if ${__T} == "amd64" || ${__T} == "i386" || ${__T} == "powerpc" || ${__T} == "arm"
 __DEFAULT_YES_OPTIONS+=CLANG
 .else

Unfortunately this doesn't mean that cross-compiling works fine now for ARM. It fails on building lib/libcompiler_rt.
Here is output if anybody have idea how to fix it: http://pastebin.com/Ly2jARjd

Damjan