Messages in this thread Patch in this message | | | From | Nathan Chancellor <> | Subject | [PATCH v5 1/3] powerpc: Don't add -mabi= flags when building with Clang | Date | Mon, 18 Nov 2019 21:57:10 -0700 |
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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> ---
v1 -> v2:
* Improve commit message
v2 -> v3:
* Rebase and merge into a single series.
v3 -> v4:
* Rebase on v5.4-rc3.
* Update links to point to llvmorg-9.0.0 instead of llvmorg-9.0.0-rc2.
v4 -> v5:
* Rebase on next-20191118
arch/powerpc/Makefile | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index a3ed4f168607..f35730548e42 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -91,11 +91,13 @@ MULTIPLEWORD := -mmultiple endif ifdef CONFIG_PPC64 +ifndef CONFIG_CC_IS_CLANG cflags-$(CONFIG_CPU_BIG_ENDIAN) += $(call cc-option,-mabi=elfv1) cflags-$(CONFIG_CPU_BIG_ENDIAN) += $(call cc-option,-mcall-aixdesc) aflags-$(CONFIG_CPU_BIG_ENDIAN) += $(call cc-option,-mabi=elfv1) aflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -mabi=elfv2 endif +endif ifndef CONFIG_CC_IS_CLANG cflags-$(CONFIG_CPU_LITTLE_ENDIAN) += -mno-strict-align @@ -141,6 +143,7 @@ endif endif CFLAGS-$(CONFIG_PPC64) := $(call cc-option,-mtraceback=no) +ifndef CONFIG_CC_IS_CLANG ifdef CONFIG_CPU_LITTLE_ENDIAN CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2,$(call cc-option,-mcall-aixdesc)) AFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv2) @@ -149,6 +152,7 @@ CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv1) CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mcall-aixdesc) AFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mabi=elfv1) endif +endif CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mcmodel=medium,$(call cc-option,-mminimal-toc)) CFLAGS-$(CONFIG_PPC64) += $(call cc-option,-mno-pointers-to-nested-functions) -- 2.24.0
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