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selftests/bpf: make BPF_TARGET_ENDIAN non-recursive to speed up *.bpf.o build

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BPF_TARGET_ENDIAN is used in CLANG_BPF_BUILD_RULE and co macros.
It is defined as a recursively expanded variable, meaning that it is
recomputed each time the value is needed. Thus, it is recomputed for
each *.bpf.o file compilation. The variable is computed by running a C
compiler in a shell. This significantly hinders parallel build
performance for *.bpf.o files.

This commit changes BPF_TARGET_ENDIAN to be a simply expanded
variable.

    # Build performance stats before this commit
    $ git clean -xfd; time make -j12
    real	1m0.000s
    ...

    # Build performance stats after this commit
    $ git clean -xfd; time make -j12
    real	0m43.605s
    ...

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20241213003224.837030-1-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2024-12-12 16:32:24 -08:00 committed by Alexei Starovoitov
parent f4f25b689b
commit 5506b7d7bb
1 changed files with 3 additions and 3 deletions
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6
tools/testing/selftests/bpf/Makefile
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@ -461,10 +461,10 @@ $(shell $(1) $(2) -dM -E - </dev/null | grep -E 'MIPS(EL|EB)|_MIPS_SZ(PTR|LONG)
endef
# Determine target endianness.
IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \
IS_LITTLE_ENDIAN := $(shell $(CC) -dM -E - </dev/null | \
grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__')
MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
BPF_TARGET_ENDIAN=$(if $(IS_LITTLE_ENDIAN),--target=bpfel,--target=bpfeb)
MENDIAN:=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
BPF_TARGET_ENDIAN:=$(if $(IS_LITTLE_ENDIAN),--target=bpfel,--target=bpfeb)
ifneq ($(CROSS_COMPILE),)
CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))