Messages in this thread | | | Date | Thu, 27 Apr 2006 16:37:36 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] likely cleanup: remove unlikely for kfree(NULL) |
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Pekka J Enberg wrote: > On Wed, 26 Apr 2006, Kyle Moffett wrote: > >>Here's code that I've found works as well as can be expected under both GCC 3 >>and GCC 4. If xp is a known-NULL constant the whole function will be >>optimized out completely. If xp is known-not-NULL, then it will optimize to a >>kfree function without the null check. Otherwise it optimizes to call the >>out-of-line version. > > > Wouldn't it be better to simply remove calls to kfree() with known > NULL constant?
Yes, but this will optimise away the check for known non-NULL.
At the cost of icache footprint.
I think unmeasurable micro-optimisations that go against historic CPU trends (eg. size for speed) aren't worth wasting too much sleep over. If it is a 0.0001% speedup today, it'll be a 0.0001% slowdown tomorrow :)
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