Date: Tue, 21 Jun 2011 11:06:17 -0600 From: Warner Losh <imp@bsdimp.com> To: Damjan Marion <damjan.marion@gmail.com> Cc: toolchain@FreeBSD.org Subject: Re: cross-compiling for arm with clang Message-ID: <AC8BF81A-2EF4-48FF-ABDE-E928C1B4A06E@bsdimp.com> In-Reply-To: <8E65FA9C-330B-4055-8959-75EE06E557E8@gmail.com> References: <D0F647ED-4AB2-4A61-AD37-423F0AF9805D@gmail.com> <C29B8240-9D19-46CC-A1FC-1B9150547B1D@bsdimp.com> <15B76B64-D26E-420D-AE37-B52A694CDF98@gmail.com> <BF24BE90-48B7-48A0-90FE-234C28AE9CA9@bsdimp.com> <8E65FA9C-330B-4055-8959-75EE06E557E8@gmail.com>
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On Jun 21, 2011, at 3:12 AM, Damjan Marion wrote: >=20 > On Jun 17, 2011, at 9:16 PM, Warner Losh wrote: >=20 >>=20 >> On Jun 17, 2011, at 12:38 PM, Damjan Marion wrote: >>=20 >>> Now, I'm back on my original problem, clang invokes /usr/bin/as = which is i386 AS instead of ARM version in obj tree. >>=20 >> That's a bogus assumption on the part of clang. At the very least, = it should be adding the magic gas flags to use the correct triple for = the platform. But if you did that, your next complaint would be that we = only build as for the native architecture and not anything else. >>=20 >>> How this works on other platforms (i.e. cross-compiling for amd64)? >>=20 >> 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). >>=20 >> It works by accident for i386 on amd64, I think. as treats the more = or less as the same. >=20 > 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. >=20 > For me it works well, even when I use clang on Darwin host, it calls = proper as/ld. >=20 > # /opt/llvm/bin/clang -ccc-host-triple arm-unknown-freebsd = -mfloat-abi=3Dsoft 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 >=20 >=20 > 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. There's a make xdev target that installs both the = /usr/arm-freebsd/usr/bin/as type files as well as symbolic links in = /usr/local/bin/arm-freebsd-as. But that target isn't part of = buildworld. It has been tested recently (it was broken for a while in = 8, and I'm not sure I've merged the patches over yet). However, it = doesn't include the extra bogus 'unknown' which if you were to have = included it breaks many of the autoconf scripts that I ran into when I = did this patch. Also, I install things as = /usr/local/bin/arm-freebsd9-as as well, since that's what we needed for = gcc compatibility. I suppose we could include a unknown thing. However, you'd need to install symlinks to make this work in a = build-world setting. > Is there any other comment to this patch[1]? >=20 >=20 > [1] = http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20110620/043072= .html Not enough of a llvm guy to know if this patch is good or bad. Warner
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