From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nathan Chancellor <natechancellor@gmail.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
Nathan Chancellor <natechancellor@gmail.com>,
linuxppc-dev@lists.ozlabs.org, Daniel Axtens <dja@axtens.net>
Subject: Re: [PATCH v5 1/3] powerpc: Don't add -mabi= flags when building with Clang
Date: Tue, 26 Nov 2019 12:13:21 +1100 (AEDT) [thread overview]
Message-ID: <47MQrd1PSrz9sPZ@ozlabs.org> (raw)
In-Reply-To: <20191119045712.39633-2-natechancellor@gmail.com>
On Tue, 2019-11-19 at 04:57:10 UTC, Nathan Chancellor wrote:
> When building pseries_defconfig, building vdso32 errors out:
>
> error: unknown target ABI 'elfv1'
>
> This happens because -m32 in clang changes the target to 32-bit,
> which does not allow the ABI to be changed, as the setABI virtual
> function is not overridden:
>
> https://github.com/llvm/llvm-project/blob/llvmorg-9.0.0/clang/include/clang/Basic/TargetInfo.h#L1073-L1078
>
> https://github.com/llvm/llvm-project/blob/llvmorg-9.0.0/clang/lib/Basic/Targets/PPC.h#L327-L365
>
> Commit 4dc831aa8813 ("powerpc: Fix compiling a BE kernel with a
> powerpc64le toolchain") added these flags to fix building big endian
> kernels with a little endian GCC.
>
> Clang doesn't need -mabi because the target triple controls the default
> value. -mlittle-endian and -mbig-endian manipulate the triple into
> either powerpc64-* or powerpc64le-*, which properly sets the default
> ABI:
>
> https://github.com/llvm/llvm-project/blob/llvmorg-9.0.0/clang/lib/Driver/Driver.cpp#L450-L463
>
> https://github.com/llvm/llvm-project/blob/llvmorg-9.0.0/llvm/lib/Support/Triple.cpp#L1432-L1516
>
> https://github.com/llvm/llvm-project/blob/llvmorg-9.0.0/clang/lib/Basic/Targets/PPC.h#L377-L383
>
> Adding a debug print out in the PPC64TargetInfo constructor after line
> 383 above shows this:
>
> $ echo | ./clang -E --target=powerpc64-linux -mbig-endian -o /dev/null -
> Default ABI: elfv1
>
> $ echo | ./clang -E --target=powerpc64-linux -mlittle-endian -o /dev/null -
> Default ABI: elfv2
>
> $ echo | ./clang -E --target=powerpc64le-linux -mbig-endian -o /dev/null -
> Default ABI: elfv1
>
> $ echo | ./clang -E --target=powerpc64le-linux -mlittle-endian -o /dev/null -
> Default ABI: elfv2
>
> Don't specify -mabi when building with clang to avoid the build error
> with -m32 and not change any code generation.
>
> -mcall-aixdesc is not an implemented flag in clang so it can be
> safely excluded as well, see commit 238abecde8ad ("powerpc: Don't
> use gcc specific options on clang").
>
> pseries_defconfig successfully builds after this patch and
> powernv_defconfig and ppc44x_defconfig don't regress.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/240
> Reviewed-by: Daniel Axtens <dja@axtens.net>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/465bfd9c44dea6b55962b5788a23ac87a467c923
cheers
next prev parent reply other threads:[~2019-11-26 1:17 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 18:20 [PATCH v3 0/3] LLVM/Clang fixes for pseries_defconfig Nathan Chancellor
2019-09-11 18:20 ` [PATCH v3 1/3] powerpc: Don't add -mabi= flags when building with Clang Nathan Chancellor
2019-09-11 18:20 ` [PATCH v3 2/3] powerpc: Avoid clang warnings around setjmp and longjmp Nathan Chancellor
2019-09-11 20:55 ` Nick Desaulniers
2019-09-11 18:20 ` [PATCH v3 3/3] powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp Nathan Chancellor
2019-09-11 21:01 ` Nick Desaulniers
2019-09-12 5:43 ` Nathan Chancellor
2019-09-12 17:30 ` Nick Desaulniers
2019-10-14 2:50 ` [PATCH v4 0/3] LLVM/Clang fixes for pseries_defconfig Nathan Chancellor
2019-10-14 2:50 ` [PATCH v4 1/3] powerpc: Don't add -mabi= flags when building with Clang Nathan Chancellor
2019-10-14 2:51 ` [PATCH v4 2/3] powerpc: Avoid clang warnings around setjmp and longjmp Nathan Chancellor
2019-10-14 2:51 ` [PATCH v4 3/3] powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp Nathan Chancellor
2019-10-14 9:35 ` Segher Boessenkool
2019-10-14 15:56 ` Nick Desaulniers
2019-10-14 19:11 ` Segher Boessenkool
2019-10-18 19:00 ` Nathan Chancellor
2019-10-18 20:02 ` Segher Boessenkool
2019-10-22 5:15 ` Nathan Chancellor
2019-10-22 8:57 ` Segher Boessenkool
2019-10-30 4:12 ` Nathan Chancellor
2019-10-14 16:03 ` [PATCH v4 0/3] LLVM/Clang fixes for pseries_defconfig Nick Desaulniers
2019-11-19 4:57 ` [PATCH v5 0/3] LLVM/Clang fixes for a few defconfigs Nathan Chancellor
2019-11-19 4:57 ` [PATCH v5 1/3] powerpc: Don't add -mabi= flags when building with Clang Nathan Chancellor
2019-11-26 1:13 ` Michael Ellerman [this message]
2019-11-19 4:57 ` [PATCH v5 2/3] powerpc: Avoid clang warnings around setjmp and longjmp Nathan Chancellor
2019-11-19 4:57 ` [PATCH v5 3/3] powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp Nathan Chancellor
2019-11-25 20:15 ` [PATCH v5 0/3] LLVM/Clang fixes for a few defconfigs Nick Desaulniers
2019-11-28 4:59 ` Michael Ellerman
2019-11-28 7:45 ` Nathan Chancellor
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