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SubjectRe: Linux 2.6.27.27


On Tue, 21 Jul 2009, Linus Torvalds wrote:
>
> Just out of curiosity, how did you find it? Now that I know where to look,
> it's very obvious in the assembler diffs, but I didn't notice it until you
> pointed it out just because there is so _much_ of the diffs...

Ahh. I think I see how you found it. Looking at the diffs, there's only a
few places where the number of instructions changed by a big fraction. And
there's only _one_ place that has a factor-of-three difference (26 lines
in the correct cases, and 7 lines in the wrong one). Clever.

There's also a case in do_page_fault() where -fno-strict-overflow
generates a _lot_ more instructions than the other cases (but not by a
factor of three - but it expands 63 instructions to 100). I'm not seeing
quite _why_ it does that, but it does various stupid things like multiply
by 0x38 etc. But it doesn't look buggy, it just looks stupid.

Or did you just brute-force it and spend a lot of time eyeballing things?

Linus


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