clang 3.4 @3.4.2_15: Build fails (incompatible cpu-subtype) on a G3. Makefile assumes altivec available in llvm-3.4.2.src/tools/clang/lib/Lex/Makefile

[evanmiller (Evan Miller)]

Log excerpt:

:info:build make/platform/clang_linux.mk:16: *** "unable to infer compiler target triple for /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build/Release/bin/clang".  Stop.
:info:build gmake[4]: Leaving directory '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/llvm-3.4.2.src/projects/compiler-rt'
:info:build gmake[3]: *** [Makefile:162: BuildRuntimeLibraries] Error 2
:info:build gmake[3]: Leaving directory '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build/tools/clang/runtime/compiler-rt'
:info:build gmake[2]: *** [/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/llvm-3.4.2.src/Makefile.rules:911: compiler-rt/.makeall] Error 2
:info:build gmake[2]: Leaving directory '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build/tools/clang/runtime'
:info:build gmake[1]: *** [/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/llvm-3.4.2.src/Makefile.rules:852: all] Error 1
:info:build gmake[1]: Leaving directory '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build/tools/clang'
:info:build gmake: *** [/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/llvm-3.4.2.src/Makefile.rules:852: all] Error 1
:info:build gmake: Leaving directory '/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build'
:info:build Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build" && /opt/local/bin/gmake -j1 -w clang-only
:info:build Exit code: 2
:error:build Failed to build clang-3.4: command execution failed
:debug:build Error code: CHILDSTATUS 9327 2
:debug:build Backtrace: command execution failed
:debug:build     while executing
:debug:build "system {*}$notty {*}$callback {*}$nice $fullcmdstring"
:debug:build     invoked from within
:debug:build "command_exec -callback portprogress::target_progress_callback build"
:debug:build     (procedure "portbuild::build_main" line 8)
:debug:build     invoked from within
:debug:build "$procedure $targetname"
:error:build See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/main.log for details.

Excerpt from the offending makefile:

Description := Static runtime libraries for clang/Linux.

###

CC := clang
Arch := unknown
Configs :=

# We don't currently have any general purpose way to target architectures other
# than the compiler defaults (because there is no generalized way to invoke
# cross compilers). For now, we just find the target architecture of the
# compiler and only define configurations we know that compiler can generate.
CompilerTargetTriple := $(shell \
    $(CC) -v 2>&1 | grep 'Target:' | cut -d' ' -f2)
ifeq ($(CompilerTargetTriple),)
$(error "unable to infer compiler target triple for $(CC)")
endif

Running the clang -v explicitly:

$ ./clang-3.4/work/build/Release/bin/clang -v
dyld: incompatible cpu-subtype

Checking it with lipo:

$ lipo -info ./clang-3.4/work/build/Release/bin/clang
Non-fat file: /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-3.4/clang-3.4/work/build/Release/bin/clang is architecture: ppc7400

It looks like GCC is emitting ppc7400 on an unsupported G3 machine, similar to #63259. I don't expect the maintainers to take up this issue, but wanted to document my findings for later.

System information:

:debug:sysinfo Mac OS X 10.4.11 (darwin/8.11.0) arch powerpc
:debug:sysinfo MacPorts 2.7.1
:debug:sysinfo Xcode 2.5
:debug:sysinfo SDK 10.4
:debug:sysinfo MACOSX_DEPLOYMENT_TARGET: 10.4

[kencu (Ken)]

apple-gcc42 usually puts out the right cpu subtype for you, otherwise nothing would run on your machine at all, so this doesn't appear to me to be an inherent error in apple-gcc42.

In fact, usually it puts out all the cpu subtypes, I believe, via cpu_subtype_all being a default setting.

in #63259, it seems gcc is being told to output Altivec code with -maltivec, so it does. That the cpu can't run it in the end seems to be a cmake logic error in libjpeg-turbo, not a gcc problem, although with further testing this might turn out to be an actual gcc error, don't know yet.

here, I dunno if anyone has ever tried to build clang-3.4 on a G3 before....I never have. Obviously somewhere apple-gcc42 is being told to put out ppc7400 code, probably by an -maltivec being thrown in somewhere in the build scripts for clang-3.4.

where exactly that might be, whether it is in multiple places, and whether clang-3.4 can be built without Altivec all remain unknown.

[evanmiller (Evan Miller)]

Yep there's an -maltivec indiscriminately added in llvm-3.4.2.src/tools/clang/lib/Lex/Makefile:

ifeq ($(ARCH),PowerPC)
CXX.Flags += -maltivec
endif

Currently trying to build with that commented out. If it works we'll likely need another (or broader) discussion about how to handle it, since there didn't seem to be a consensus about variants vs host checking with regard to libjpeg-turbo.

In the clang-3.4 case, it might be possible to pass in -mno-altivec without patching source – in my testing, this flag will override a prior -maltivec flag.

[kencu (Ken)]

gcc will have some logic for handling conflicting flags being passes into it. Usually, that means taking the last flag as the one to obey.

[evanmiller (Evan Miller)]

Good news - commenting out the CXX.Flags += -maltivec line does fix the build on the G3. But I'm really not sure how to proceed here – maybe worth opening a separate ticket to discuss the general G3 vs Altivec issue?

[kencu (Ken)]

FWIW, all versions of clang are unable to build anything useful on PPC, G3, G4, or G5 -- the PPC code generator in LLVM is broken when it comes to the Darwin PPC ABI.

G3 altivec hiccups appear to be a port-by-port issue, like this flag added in clang-3.4 assuming altivec, or the broken cmake system altivec test in libjpeg-turbo. It is not a general MacPorts issue, although no doubt you'll find more ports that assume altivec if they support ppc at all.

[kencu (Ken)]

In c22ae68c2fcc1039046536fdb2448a26f635665d/macports-ports (master):

clang-3.4: fix build on G3 Tiger

if this machine is a G3, don't assume Altivec, and also force a local build
so we don't download a buildbot-built version possibly built on a G4+
or cross-compiled from an Intel system

closes: #63304