[RFC] external compiler support

Warner Losh imp at bsdimp.com
Wed Feb 27 15:57:18 UTC 2013


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.

> -- Brooks
> 
> -----
> MFP4 222356, 222371, 222375, 222391, 222403, 222407, 222411
> 
> Add support for an external cross compiler.  The cross compiler is
> specified by passing the XCC, XCXX, and XCPP variables (corresponding to
> CC, CXX, and CPP) to buildworld/buildkernel.  The compiler must be clang
> or be configured to target the appropriate architecture.
> 
> To speed build times, if XCC is an absolute path or
> WITHOUT_CROSS_COMPILER is defined then no cross compiler will be built
> during the cross-tools stage.

This change is likely good as-is.

> To facilitate the use of unmodified external compilers, a
> WITHOUT_FORMAT_EXTENSIONS option is available to supress printf format
> checking.

This one definitely is good as-is.

> As a short-term measure, supress a few new clang warnings during kernel
> builds.
> 
> Sponsored by:	DARPA, AFRL
> Reviewed by:	xxx
> 
> --- ../../freebsd/src/Makefile.inc1	2013-02-26 21:31:09.000000000 +0000
> +++ ./Makefile.inc1	2013-02-26 21:10:50.000000000 +0000
> @@ -280,16 +280,34 @@
> .if ${MK_CDDL} == "no"
> WMAKEENV+=	NO_CTF=1
> .endif
> -.if ${CC:T:Mgcc} == "gcc"
> +XCC?=	${CC}
> +XCXX?=	${CXX}
> +XCPP?=	${CPP}

I don't like having three different variables to set. I don't think this will work with gcc, unless we've fixed all the instances in the tree where we called AS or LD directly.  The patches that I had would set ${CC}, etc based on a CROSS_COMPILER_PATH=xxx variable. I'd rather see us do that than have this hacky set 3 variables thing.

> +.if ${XCC:T:Mgcc} == "gcc"
> WMAKE_COMPILER_TYPE=	gcc
> -.elif ${CC:T:Mclang} == "clang"
> +.elif ${XCC:T:Mclang} == "clang"
> WMAKE_COMPILER_TYPE=	clang
> .elif ${MK_CLANG_IS_CC} == "no"
> WMAKE_COMPILER_TYPE=	gcc
> .else
> WMAKE_COMPILER_TYPE=	clang
> .endif

Is there any way to set the WMAKE_COMPILER_TYPE with these patches? XCC might be something like mips-cavium-cc which won't trigger any of the above, unless you also have set WITHOUT_CLANG_IS_CC...

> -WMAKEENV+=	COMPILER_TYPE=${WMAKE_COMPILER_TYPE}
> +.if ${XCC:M/*}
> +XFLAGS=		--sysroot=${WORLDTMP} -B${WORLDTMP}/usr/bin
> +.if ${TARGET_ARCH} != ${MACHINE_ARCH} && ${WMAKE_COMPILER_TYPE} == "clang"
> +.if (${TARGET_ARCH} == "arm" || ${TARGET_ARCH} == "armv6") && \
> +${MK_ARM_EABI} != "no"
> +TARGET_ABI=	gnueabi
> +.else
> +TARGET_ABI=	unknown
> +.endif

We need to fix the gnueabi issue with arm.  machine_arch should always be enough to be self-hosting, and while I fixed the armv6 issue, this has cropped up in its place :(.

> +TARGET_TRIPLE?=	${TARGET_ARCH:C/amd64/x86_64/}-${TARGET_ABI}-freebsd10.0
> +XFLAGS+=	-target ${TARGET_TRIPLE}
> +.endif
> +.endif
> +WMAKEENV+=	CC="${XCC} ${XFLAGS}" CXX="${XCXX} ${XFLAGS}" \
> +		CPP="${XCPP} ${XFLAGS}" \
> +		COMPILER_TYPE=${WMAKE_COMPILER_TYPE}
> WMAKE=		${WMAKEENV} ${MAKE} ${WORLD_FLAGS} -f Makefile.inc1 DESTDIR=${WORLDTMP}
> 
> .if ${TARGET_ARCH} == "amd64" || ${TARGET_ARCH} == "powerpc64"
> @@ -321,6 +339,7 @@
> 
> 
> LIB32FLAGS=	-m32 ${LIB32CPUFLAGS} -DCOMPAT_32BIT \
> +		--sysroot=${WORLDTMP} \
> 		-isystem ${LIB32TMP}/usr/include/ \
> 		-L${LIB32TMP}/usr/lib32 \
> 		-B${LIB32TMP}/usr/lib32
> @@ -336,8 +355,8 @@
> 		SHLIBDIR=/usr/lib32 \
> 		COMPILER_TYPE=${WMAKE_COMPILER_TYPE}
> LIB32WMAKEFLAGS+=	\
> -		CC="${CC} ${LIB32FLAGS}" \
> -		CXX="${CXX} ${LIB32FLAGS}" \
> +		CC="${XCC} ${LIB32FLAGS}" \
> +		CXX="${XCXX} ${LIB32FLAGS}" \
> 		DESTDIR=${LIB32TMP} \
> 		-DCOMPAT_32BIT \
> 		-DLIBRARIES_ONLY \
> @@ -1288,6 +1307,9 @@
> _binutils=	gnu/usr.bin/binutils
> .endif
> 
> +# If an full path to an external cross compiler is given, don't build
> +# a cross compiler.
> +.if ${XCC:M/*} == "" && ${MK_CROSS_COMPILER} != "no"
> .if ${MK_CLANG} != "no" && (${MK_CLANG_IS_CC} != "no" || ${CC:T:Mclang} == "clang")
> _clang=		usr.bin/clang
> _clang_libs=	lib/clang
> @@ -1296,6 +1318,7 @@
> .if ${MK_GCC} != "no" && (${MK_CLANG_IS_CC} == "no" || ${TARGET} == "pc98")
> _cc=		gnu/usr.bin/cc
> .endif
> +.endif
> 
> cross-tools:
> .for _tool in \
> --- ../../freebsd/src/share/mk/bsd.own.mk	2013-02-15 18:49:13.000000000 +0000
> +++ share/mk/bsd.own.mk	2013-02-26 21:10:50.000000000 +0000
> @@ -262,6 +262,7 @@
>     CAPSICUM \
>     CDDL \
>     CPP \
> +    CROSS_COMPILER \
>     CRYPT \
>     CTM \
>     CVS \
> @@ -271,6 +272,7 @@
>     ED_CRYPTO \
>     EXAMPLES \
>     FLOPPY \
> +    FORMAT_EXTENSIONS \
>     FORTH \
>     FP_LIBC \
>     FREEBSD_UPDATE \
> --- ../../freebsd/src/sys/conf/kern.mk	2012-11-11 22:15:16.000000000 +0000
> +++ sys/conf/kern.mk	2013-02-26 20:35:48.000000000 +0000
> @@ -5,7 +5,7 @@
> #
> CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
> 		-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
> -		-Wundef -Wno-pointer-sign -fformat-extensions \
> +		-Wundef -Wno-pointer-sign ${FORMAT_EXTENTIONS} \
> 		-Wmissing-include-dirs -fdiagnostics-show-option \
> 		${CWARNEXTRA}
> #
> @@ -29,7 +29,18 @@
> # enough to error out the whole kernel build.  Display them anyway, so there is
> # some incentive to fix them eventually.
> CWARNEXTRA?=	-Wno-error-tautological-compare -Wno-error-empty-body \
> -		-Wno-error-parentheses-equality
> +		-Wno-error-parentheses-equality \
> +		-Wno-sizeof-pointer-memaccess \
> +		-Wno-unused-command-line-argument \
> +		${NO_WFORMAT}
> +.endif
> +
> +# External compilers may not support our format extensions.  Allow them
> +# to be disabled.  WARNING: format checking is disabled in this case.
> +.if ${MK_FORMAT_EXTENSIONS} == "no"
> +NO_WFORMAT=		-Wno-format
> +.else
> +FORMAT_EXTENTIONS=	-fformat-extensions
> .endif
> 
> #
> diff -uN ../../freebsd/src/tools/build/options/WITHOUT_CROSS_COMPILER tools/build/options/WITHOUT_CROSS_COMPILER
> --- ../../freebsd/src/tools/build/options/WITHOUT_CROSS_COMPILER	1970-01-01 00:00:00.000000000 +0000
> +++ tools/build/options/WITHOUT_CROSS_COMPILER	2013-02-26 21:10:50.000000000 +0000
> @@ -0,0 +1,3 @@
> +.\" $FreeBSD$
> +Set to not build a cross compiler in the cross-tools stage of
> +buildworld, buildkernel, etc.
> diff -uN ../../freebsd/src/tools/build/options/WITHOUT_FORMAT_EXTENSIONS tools/build/options/WITHOUT_FORMAT_EXTENSIONS
> --- ../../freebsd/src/tools/build/options/WITHOUT_FORMAT_EXTENSIONS	1970-01-01 00:00:00.000000000 +0000
> +++ tools/build/options/WITHOUT_FORMAT_EXTENSIONS	2013-02-26 20:35:48.000000000 +0000
> @@ -0,0 +1,5 @@
> +.\" $FreeBSD$
> +Set to not enable
> +.Fl fformat-extensions
> +when compiling the kernel.
> +Also disables all format checking.



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