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 $$?),0) This is more expensive than using built-in functions since it forks a process. If we know the two have the same number of digits, we can do better. This commit adds four macros, test-le, test-ge, test-lt, test-gt. $(call test-lt, A, B) is evaluated to 'y' if A is less than B, or empty otherwise. This will replace $(call shell test A -lt B). Again, the limitation is that A and B must have the same number of digits because these macros are based on $(sort ) function. $(call test-lt, 1, 9) --> y (Works!) $(call test-lt, 10, 9) --> y (Not work...) To make the latter work, you need to add '0' prefix to align the number of digits: $(call test-lt, 10, 09) --> empty (Works!) Actually, we can live with this limitation in many places. As for the example above, we know $(CONFIG_LLD_VERSION) is 6-digits because the minimal supported version of LLVM is 11.0.0 (or CONFIG_LLD_VERSION=0 if the linker is not LLD, this case also works.) So, the shell invocation can be replaced with more efficient code: ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 130000),y) Of course, this assumption will break when LLVM 100 is released, but it will be far in the future. Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx> --- Changes in v3: - Ensure the given parameters are not empty Makefile | 2 +- arch/riscv/Makefile | 2 +- arch/x86/Makefile | 2 +- scripts/Kbuild.include | 10 ++++++++++ 4 files changed, 13 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index 6f846b1f2618..eb80332f7b51 100644 --- a/Makefile +++ b/Makefile @@ -986,7 +986,7 @@ KBUILD_LDFLAGS += -mllvm -import-instr-limit=5 # Check for frame size exceeding threshold during prolog/epilog insertion # when using lld < 13.0.0. ifneq ($(CONFIG_FRAME_WARN),0) -ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),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
