mbox series

[v4,0/4] pass -march= only to compiler

Message ID 20221014201354.3190007-1-ndesaulniers@google.com (mailing list archive)
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Series pass -march= only to compiler | expand

Message

Nick Desaulniers Oct. 14, 2022, 8:13 p.m. UTC 
When both -march= and -Wa,-march= are specified for assembler or
assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march=
value but Clang will warn that -march= is unused.

warning: argument unused during compilation: '-march=armv6k'
[-Wunused-command-line-argument]

This is the top group of warnings we observe when using clang to
assemble the kernel via `ARCH=arm make LLVM=1`.

Arnd sent a v2 of my previous patch
https://lore.kernel.org/linux-arm-kernel/20210928154143.2106903-14-arnd@kernel.org/
I added yet a few more instances I found since then. Nathan pointed out
a new one too that I've fixed since v3.

Fixing this will allow us to enable
-Werror=unused-command-line-argument for clang builds.

v3 had an issue wrt. __thumb2__
https://lore.kernel.org/llvm/CAKwvOdmkd2PxvMUZA=A-72eATGDZkqDj--Bv1W+Xt_K_LWdROA@mail.gmail.com/
I've incorporated idea from Nathan and Ard on that.

Nick Desaulniers (4):
  ARM: remove lazy evaluation in Makefile
  ARM: use .arch directives instead of assembler command line flags
  ARM: only use -mtp=cp15 for the compiler
  ARM: pass -march= only to compiler

 arch/arm/Makefile                   | 78 ++++++++++++++++-------------
 arch/arm/boot/compressed/Makefile   |  1 -
 arch/arm/common/Makefile            |  2 -
 arch/arm/common/mcpm_head.S         |  2 +
 arch/arm/common/vlock.S             |  2 +
 arch/arm/kernel/Makefile            |  2 -
 arch/arm/kernel/hyp-stub.S          |  2 +
 arch/arm/kernel/swp_emulate.c       |  1 +
 arch/arm/lib/Makefile               |  4 --
 arch/arm/lib/delay-loop.S           |  4 ++
 arch/arm/mach-at91/Makefile         |  3 --
 arch/arm/mach-at91/pm_suspend.S     |  4 ++
 arch/arm/mach-imx/Makefile          |  3 --
 arch/arm/mach-imx/headsmp.S         |  2 +
 arch/arm/mach-imx/resume-imx6.S     |  2 +
 arch/arm/mach-imx/suspend-imx6.S    |  2 +
 arch/arm/mach-mvebu/Makefile        |  3 --
 arch/arm/mach-mvebu/coherency_ll.S  |  1 +
 arch/arm/mach-mvebu/pmsu.c          |  1 +
 arch/arm/mach-npcm/Makefile         |  2 -
 arch/arm/mach-npcm/headsmp.S        |  2 +
 arch/arm/mach-tegra/Makefile        |  2 -
 arch/arm/mach-tegra/reset-handler.S |  2 +
 arch/arm/mach-tegra/sleep-tegra20.S |  2 +
 arch/arm/mach-tegra/sleep-tegra30.S |  2 +
 arch/arm/mach-tegra/sleep.S         |  2 +
 arch/arm/mm/Makefile                | 15 ------
 arch/arm/mm/abort-ev6.S             |  1 +
 arch/arm/mm/abort-ev7.S             |  1 +
 arch/arm/mm/cache-v6.S              |  2 +
 arch/arm/mm/cache-v7.S              |  2 +
 arch/arm/mm/cache-v7m.S             |  2 +
 arch/arm/mm/copypage-feroceon.c     |  1 +
 arch/arm/mm/proc-v6.S               |  2 +
 arch/arm/mm/proc-v7-2level.S        |  2 +
 arch/arm/mm/proc-v7.S               |  2 +
 arch/arm/mm/tlb-v6.S                |  2 +
 arch/arm/mm/tlb-v7.S                |  2 +
 drivers/memory/Makefile             |  2 -
 drivers/memory/ti-emif-sram-pm.S    |  1 +
 drivers/soc/bcm/brcmstb/pm/Makefile |  1 -
 drivers/soc/bcm/brcmstb/pm/s2-arm.S |  1 +
 42 files changed, 97 insertions(+), 75 deletions(-)

Comments

Nick Desaulniers Oct. 14, 2022, 8:16 p.m. UTC | #1 
On Fri, Oct 14, 2022 at 1:14 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> When both -march= and -Wa,-march= are specified for assembler or
> assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march=
> value but Clang will warn that -march= is unused.
>
> warning: argument unused during compilation: '-march=armv6k'
> [-Wunused-command-line-argument]
>
> This is the top group of warnings we observe when using clang to
> assemble the kernel via `ARCH=arm make LLVM=1`.
>
> Arnd sent a v2 of my previous patch
> https://lore.kernel.org/linux-arm-kernel/20210928154143.2106903-14-arnd@kernel.org/
> I added yet a few more instances I found since then. Nathan pointed out
> a new one too that I've fixed since v3.
>
> Fixing this will allow us to enable
> -Werror=unused-command-line-argument for clang builds.
>
> v3 had an issue wrt. __thumb2__
> https://lore.kernel.org/llvm/CAKwvOdmkd2PxvMUZA=A-72eATGDZkqDj--Bv1W+Xt_K_LWdROA@mail.gmail.com/
> I've incorporated idea from Nathan and Ard on that.

I probably should have made a note: the base of this series is a
little funny.  It's based on today's linux-next (20221014) but with
0a7606a9832ab375a38425a659bda13712ca89ae reverted.  It sounds like
0a7606a9832ab375a38425a659bda13712ca89ae might be dropped from -next
imminently
https://lore.kernel.org/linux-next/CAK7LNARg8OpqLR_71PJV3ZoLuDV8+mz9mphg=CzEeEEMY0G3rw@mail.gmail.com/.