Date: Wed, 27 Feb 2013 14:47:59 -0700 From: Warner Losh <imp@bsdimp.com> To: Brooks Davis <brooks@FreeBSD.org> Cc: freebsd-arch@FreeBSD.org Subject: Re: [RFC] external compiler support Message-ID: <1CC1DB5A-E87A-456C-AD2C-E203146BB736@bsdimp.com> In-Reply-To: <20130227214445.GA19594@lor.one-eyed-alien.net> References: <20130227003517.GB7348@lor.one-eyed-alien.net> <28404C12-67F3-44F0-AB28-02B749472873@bsdimp.com> <51BB3E17-128A-4989-B272-D8B40D4B854B@bsdimp.com> <20130227190804.GB17489@lor.one-eyed-alien.net> <13FB8CB0-9937-4BD8-AE89-0D24494D8663@bsdimp.com> <20130227214445.GA19594@lor.one-eyed-alien.net>
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On Feb 27, 2013, at 2:44 PM, Brooks Davis wrote: > On Wed, Feb 27, 2013 at 02:01:42PM -0700, Warner Losh wrote: >> >> On Feb 27, 2013, at 12:08 PM, Brooks Davis wrote: >> >>> On Wed, Feb 27, 2013 at 09:08:05AM -0700, Warner Losh wrote: >>>> Ooops, forgot to add one item.. >>>> >>>> >>>> On Feb 27, 2013, at 8:57 AM, Warner Losh wrote: >>>> >>>>> >>>>> On Feb 26, 2013, at 5:35 PM, Brooks Davis wrote: >>>>> >>>>>> Below (and at http://people.freebsd.org/~brooks/patches/xcc.diff) you >>>>>> can find an initial patch with proposed commit for external compiler >>>>>> support. It relies on the existing cross binutils as I'm finding that >>>>>> the two are fairly separable. With this patch I've been able to build >>>>>> from amd64 to arm, amd64, and i386 using clang from the lang/clang-devel >>>>>> port. I've also compiled the tree with a customized clang being >>>>>> developed at the University of Cambridge. >>>>> >>>>> Cool! >>>>> >>>>>> The patch is untested with gcc. >>>>> >>>>> I'd like to see it tested with gcc :) >>>>> >>>>>> Does this seem like a reasonable approach? I do plan to look at external >>>>>> binutils support, but it's not on the critical path for our current work >>>>>> so I've opted to avoid it for now. >>>>> >>>>> The patches I posted a few months ago had that as well... >>>>> >>>>>> As a bonus for those who don't need an external compiler, but do run >>>>>> make buildworld frequently, the XCC, XCXX, and XCPP variables can be set >>>>>> to the location of the installed base system compiler to avoid building >>>>>> the compiler twice during buildworld. >>>>> >>>>> I think this will work, but it is kludgy. I had created a __X=<prefix-path> which was prepended to ${CC}, et al, in sys.mk. It was only defined when you set CROSS_COMPILER_PATH (or EXTERNAL_COMPILER_PATH, I forget) during the cross building stage. It also had the advantage of making external cross binutils available. Your patch could fairly easily use this interface instead of having to set 3 different variables, which will morph to 10 when you add binutil support. >>>> >>> >>> I think something like this will have to be done for binutils given the >>> way -B works, but I don't think it's workable in the general compiler >>> case because I want to be able to use gcc46 or a future clang33 or >>> similar as CC without changing the system compiler. Ideally I'd >>> also like to support clang's method of finding appropriate binutils >>> by looking first for /binutils/path/${TARGET_TRIPLE}-tool and then >>> /binutils/path/tool. >> >> I didn't know that clang did this, but that's certainly doable. > > The key is that for it to work we need to set each tool's name > individually. > >>> As a strawman, let's say we add a CROSS_COMPILER_PATH and a >>> CROSS_BINUTILS_PATH. The former will set XCC, XCXX, and XCPP if they >>> are unset. The latter will control -B and set the various binutils >>> variables (XNM, XLD, etc). >> >> I'm not sure I like splitting things like that. It is unnatural. > > That's the traditional view with lots of historic merit. At least in > the short term it's not a useful view for me. I want to be able to > use our existing infrastructure to build a cross binutils and then use > it with an external compiler. In a clang world, we currently have one > compiler and many binutils unless we gratuitously build many compilers > as the FreeBSD build system currently does. Some day we will likely have > an all-llvm toolchain available and then we will have one toolchain for > all supported architectures. > > I suppose could hack what I want to do into the traditional single > toolchain world view by build a mips64 xdev toolchain and then building > a linkfarm and/or set of wrapper scripts to it and the clang I want to > include, but that seems problematic from a reproducability perspective > (not to mention performance if I need wrappers to set -B). > > Having a CROSS_TOOLCHAIN_PATH path that sets both would probably be a > useful compromise in this regard. Are you suggesting something like: CROSS_COMPILER_PATH?=${CROSS_TOOLCHAIN_PATH} CROSS_BINUTILS_PATH?=${CROSS_TOOLCHAIN_PATH} If so, I'd agree, that would be a very useful compromise: hits my ease of use issues, and lets you do what you need on the theory that others will likely need it too. Warner
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