lkml.org 
[lkml]   [2017]   [Mar]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/7] Makefile, x86, LLVM: disable unsupported optimization flags
From
Date
On 03/16/17 17:15, Michael Davidson wrote:
> Unfortunately, while clang generates a warning about these flags
> being unsupported it still exits with a status of 0 so we have
> to explicitly disable them instead of just using a cc-option check.
>
> Signed-off-by: Michael Davidson <md@google.com>
> ---
> Makefile | 2 ++
> arch/x86/Makefile | 2 ++
> 2 files changed, 4 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index b21fd0ca2946..5e97e5fc1eea 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -629,7 +629,9 @@ ARCH_AFLAGS :=
> ARCH_CFLAGS :=
> include arch/$(SRCARCH)/Makefile
>
> +ifneq ($(cc-name),clang)
> KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
> +endif
> KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
>
> ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 2d449337a360..894a8d18bf97 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -87,11 +87,13 @@ else
> KBUILD_AFLAGS += -m64
> KBUILD_CFLAGS += -m64
>
> +ifneq ($(cc-name),clang)
> # Align jump targets to 1 byte, not the default 16 bytes:
> KBUILD_CFLAGS += -falign-jumps=1
>
> # Pack loops tightly as well:
> KBUILD_CFLAGS += -falign-loops=1
> +endif
>
> # Don't autogenerate traditional x87 instructions
> KBUILD_CFLAGS += $(call cc-option,-mno-80387)
>

NAK. Fix your compiler, or use a wrapper script or something. It is
absolutely *not* acceptable to disable this since future versions of
clang *should* support that.

That being said, it might make sense to look for a key pattern like
"(un|not )supported" on stderr the try-run macro. Is there really no
-Wno- or -Werror= option to turn off this craziness?

-hpa

\
 
 \ /
  Last update: 2017-03-17 22:44    [W:0.460 / U:0.932 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site