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Message-Id: <20221126225624.751661-1-masahiroy@kernel.org> Date: Sun, 27 Nov 2022 07:56:20 +0900 From: Masahiro Yamada <masahiroy@...nel.org> To: linux-kbuild@...r.kernel.org Cc: linux-kernel@...r.kernel.org, Masahiro Yamada <masahiroy@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, Albert Ou <aou@...s.berkeley.edu>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Thomas Gleixner <tglx@...utronix.de>, Tom Rix <trix@...hat.com>, linux-riscv@...ts.infradead.org, llvm@...ts.linux.dev, x86@...nel.org Subject: [PATCH v3 1/5] kbuild: add test-{le,ge,lt,gt} macros Because GNU Make is handle strings, it is very hard to perform math in Makefiles. When we compare two integers, we invokes shell. One example is in the top Makefile: ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0) This is more expensive than using built-in functions since it forks a process. If we know the two have the same number of digits, we can do better. This commit adds four macros, test-le, test-ge, test-lt, test-gt. $(call test-lt, A, B) is evaluated to 'y' if A is less than B, or empty otherwise. This will replace $(call shell test A -lt B). Again, the limitation is that A and B must have the same number of digits because these macros are based on $(sort ) function. $(call test-lt, 1, 9) --> y (Works!) $(call test-lt, 10, 9) --> y (Not work...) To make the latter work, you need to add '0' prefix to align the number of digits: $(call test-lt, 10, 09) --> empty (Works!) Actually, we can live with this limitation in many places. As for the example above, we know $(CONFIG_LLD_VERSION) is 6-digits because the minimal supported version of LLVM is 11.0.0 (or CONFIG_LLD_VERSION=0 if the linker is not LLD, this case also works.) So, the shell invocation can be replaced with more efficient code: ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y) Of course, this assumption will break when LLVM 100 is released, but it will be far in the future. Signed-off-by: Masahiro Yamada <masahiroy@...nel.org> Reviewed-by: Nicolas Schier <nicolas@...sle.eu> --- Changes in v3: - Ensure the given parameters are not empty Makefile | 2 +- arch/riscv/Makefile | 2 +- arch/x86/Makefile | 2 +- scripts/Kbuild.include | 10 ++++++++++ 4 files changed, 13 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index 6f846b1f2618..eb80332f7b51 100644 --- a/Makefile +++ b/Makefile @@ -986,7 +986,7 @@ KBUILD_LDFLAGS += -mllvm -import-instr-limit=5 # Check for frame size exceeding threshold during prolog/epilog insertion # when using lld < 13.0.0. ifneq ($(CONFIG_FRAME_WARN),0) -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0) +ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y) KBUILD_LDFLAGS += -plugin-opt=-warn-stack-size=$(CONFIG_FRAME_WARN) endif endif diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index 0d13b597cb55..faf2c2177094 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -37,7 +37,7 @@ else endif ifeq ($(CONFIG_LD_IS_LLD),y) -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 150000; echo $$?),0) +ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 150000),y) KBUILD_CFLAGS += -mno-relax KBUILD_AFLAGS += -mno-relax ifndef CONFIG_AS_IS_LLVM diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 415a5d138de4..e72c7a49cd59 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -211,7 +211,7 @@ endif KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE) ifdef CONFIG_LTO_CLANG -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0) +ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y) KBUILD_LDFLAGS += -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8) endif endif diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index cbe28744637b..4b8cf464b53b 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -11,6 +11,16 @@ space := $(empty) $(empty) space_escape := _-_SPACE_-_ pound := \# +### +# Comparison macros. +# Usage: $(call test-le, A, B) +# works like shell's "test A -le B", use with care bacause it is ASCII sort. +# If A and B have the same number of digits, it works as expected. +test-le = $(and $(strip $1),$(strip $2),$(filter $1, $(firstword $(sort $1 $2))),y) +test-ge = $(call test-le, $2, $1) +test-lt = $(and $(strip $1),$(strip $2),$(filter-out $2, $(firstword $(sort $1 $2))),y) +test-gt = $(call test-lt, $2, $1) + ### # Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o dot-target = $(dir $@).$(notdir $@) -- 2.34.1
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