[PATCH -next v21 23/27] riscv: detect assembler support for .option arch

[Andy Chiu]

Some extensions use .option arch directive to selectively enable certain
extensions in parts of its assembly code. For example, Zbb uses it to
inform assmebler to emit bit manipulation instructions. However,
supporting of this directive only exist on GNU assembler and has not
landed on clang at the moment, making TOOLCHAIN_HAS_ZBB depend on
AS_IS_GNU.

While it is still under review at https://reviews.llvm.org/D123515, the
upcoming Vector patch also requires this feature in assembler. Thus,
provide Kconfig AS_HAS_OPTION_ARCH to detect such feature. Then
TOOLCHAIN_HAS_XXX will be turned on automatically when the feature land.

Suggested-by: Nathan Chancellor <nathan at kernel.org>
Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
Reviewed-by: Conor Dooley <conor.dooley at microchip.com>
Reviewed-by: Nathan Chancellor <nathan at kernel.org>
Reviewed-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
---
 arch/riscv/Kconfig | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 348c0fa1fc8c..1019b519d590 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -262,6 +262,12 @@ config RISCV_DMA_NONCOHERENT
 config AS_HAS_INSN
 	def_bool $(as-instr,.insn r 51$(comma) 0$(comma) 0$(comma) t0$(comma) t0$(comma) zero)
 
+config AS_HAS_OPTION_ARCH
+	# https://reviews.llvm.org/D123515
+	def_bool y
+	depends on $(as-instr, .option arch$(comma) +m)
+	depends on !$(as-instr, .option arch$(comma) -i)
+
 source "arch/riscv/Kconfig.socs"
 source "arch/riscv/Kconfig.errata"
 
@@ -466,7 +472,7 @@ config TOOLCHAIN_HAS_ZBB
 	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zbb)
 	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbb)
 	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
-	depends on AS_IS_GNU
+	depends on AS_HAS_OPTION_ARCH
 
 config RISCV_ISA_ZBB
 	bool "Zbb extension support for bit manipulation instructions"
-- 
2.17.1