GCC missing obvious optimizations on x86

         Give up on pushing CC_OPTIMIZE_FOR_SIZE

I still happen to believe that I$ miss costs are a major thing, but

sadly, -Os doesn't seem to be the solution. With or without it, gcc

will miss some obvious code size improvements, and with it enabled gcc

will sometimes make choices that aren't good even with high I$ miss

ratios.

For example, with -Os, gcc on x86 will turn a 20-byte constant memcpy

into a "rep movsl". While I sincerely hope that x86 CPU's will some day

do a good job at that, they certainly don't do it yet, and the cost is

higher than a L1 I$ miss would be.

Some day I hope we can re-enable this.

Signed-off-by: Linus Torvalds

Reference:  Linux Kernel GIT