[PATCH 02/22] kbuild: Add support for 'as-instr' to be used in Kconfig files

[Catalin Marinas <catalin.marinas@arm.com>]

Similar to 'cc-option' or 'ld-option', it is occasionally necessary to
check whether the assembler supports certain ISA extensions. In the
arm64 code we currently do this in Makefile with an additional define:

lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)

Add the 'as-instr' option so that it can be used in Kconfig directly:

	def_bool $(as-instr,.arch_extension lse)

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kbuild@vger.kernel.org
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 scripts/Kconfig.include | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index d4adfbe42690..9d07e59cbdf7 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -31,6 +31,10 @@ cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /de
 # Return y if the linker supports <flag>, n otherwise
 ld-option = $(success,$(LD) -v $(1))
 
+# $(as-instr,<instr>)
+# Return y if the assembler supports <instr>, n otherwise
+as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
+
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
 $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)