Re: [PATCH] Revert "kbuild: use -Oz instead of -Os when using clang"

[hpa@zytor.com]

On March 18, 2019 2:56:05 PM PDT, Matthias Kaehlcke <mka@chromium.org> wrote:
>On Mon, Mar 18, 2019 at 02:47:13PM -0700, 'Nick Desaulniers' via Clang
>Built Linux wrote:
>> On Mon, Mar 18, 2019 at 2:10 PM Matthias Kaehlcke <mka@chromium.org>
>wrote:
>> >
>> > The clang option -Oz enables *aggressive* optimization for size,
>> > which doesn't necessarily result in smaller images, but can have
>> > negative impact on performance. Switch back to the less aggressive
>> > -Os.
>> >
>> > This reverts commit 6748cb3c299de1ffbe56733647b01dbcc398c419.
>> 
>> Does scripts/checkpatch.pl complain about this format (full sha, no
>> title)?
>
>Nope, for reverts checkpatch is happy with it, I suppose because by
>default the subject of the reverted patch is part of the revert's
>subject.
>
>> Not sure that necessitates a v2, but if so would be good to
>> mention that Clang generates excessive calls into libgcc/compiler-rt
>> at -Oz.  Thanks for the patch and the discussion/sanity check.
>
>I can send a v2 if 'needed'.
>
>> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
>Thanks!
>
>Matthias
>
>> >
>> > Suggested-by: Peter Zijlstra <peterz@infradead.org>
>> > Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
>> > ---
>> >  Makefile | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/Makefile b/Makefile
>> > index 9ef547fc7ffe..191f3ce3cb5e 100644
>> > --- a/Makefile
>> > +++ b/Makefile
>> > @@ -667,7 +667,7 @@ KBUILD_CFLAGS       += $(call
>cc-disable-warning, format-overflow)
>> >  KBUILD_CFLAGS  += $(call cc-disable-warning, int-in-bool-context)
>> >
>> >  ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
>> > -KBUILD_CFLAGS  += $(call cc-option,-Oz,-Os)
>> > +KBUILD_CFLAGS  += -Os
>> >  else
>> >  KBUILD_CFLAGS   += -O2
>> >  endif
>> 
>> 
>> 

Would be nice, still, to have -Ok.
-- 
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