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Tell the world we gave up on pushing CC_OPTIMIZE_FOR_SIZE

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In commit 281dc5c5ec ("Give up on pushing CC_OPTIMIZE_FOR_SIZE") we
already changed the actual default value, but the help-text still
suggested 'y'. Fix the help text too, for all the same reasons.

Sadly, -Os keeps on generating some very suboptimal code for certain
cases, to the point where any I$ miss upside is swamped by the downside.
The main ones are:

 - using "rep movsb" for memcpy, even on CPU's where that is
   horrendously bad for performance.

 - not honoring branch prediction information, so any I$ footprint you
   win from smaller code, you lose from less code density in the I$.

 - using divide instructions when that is very expensive.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill Smelkov 2012-11-02 15:41:01 +04:00 committed by Linus Torvalds
parent fbfc23ef90
commit 3a55fb0d9f
1 changed files with 1 additions and 1 deletions
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2
init/Kconfig
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@ -1182,7 +1182,7 @@ config CC_OPTIMIZE_FOR_SIZE
Enabling this option will pass "-Os" instead of "-O2" to gcc
resulting in a smaller kernel.
If unsure, say Y.
If unsure, say N.
config SYSCTL
bool