Messages in this thread | | | Date | Sat, 11 Apr 2015 15:48:57 +0200 | From | Markus Trippelsdorf <> | Subject | Re: [PATCH] x86: Align jump targets to 1 byte boundaries |
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On 2015.04.10 at 14:50 +0200, Denys Vlasenko wrote: > New-ish versions of gcc allow people to specify optimization > options per function: > > https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#Function-Attributes > > optimize > The optimize attribute is used to specify that a function is to be compiled > with different optimization options than specified on the command line. > Arguments can either be numbers or strings. Numbers are assumed to be an > optimization level. Strings that begin with O are assumed to be an > optimization option, while other options are assumed to be used with > a -f prefix. > > How about not aligning code by default, and using > > #define hot_func __attribute__((optimize("O2","align-functions=16","align-jumps=16"))) > ... > > void hot_func super_often_called_func(...) {...} > > in hot code paths?
__attribute__((optimize)) is meant for compiler debugging only (to help folks to reduce their testcases to a single function). It should _not_ be used in production code, because the implementation is very buggy.
-- Markus
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