mirror of https://gitee.com/openkylin/linux.git
ae37a8cd9b
__pure is used to make gcc do Common Subexpression Elimination (CSE) and thus save subsequent invocations of a function which does a complex computation (without side effects). As a simple example: bool a = _static_cpu_has(x); bool b = _static_cpu_has(x); gets turned into bool a = _static_cpu_has(x); bool b = a; However, gcc doesn't do CSE with asm()s when those get inlined - like it is done with _static_cpu_has() - because, for example, the t_yes/t_no labels are different for each inlined function body and thus cannot be detected as equivalent anymore for the CSE heuristic to hit. However, this all is beside the point because best it should be avoided to have more than one call to _static_cpu_has(X) in the same function due to the fact that each such call is an alternatives patch site and it is simply pointless. Therefore, drop the __pure attribute as it is not doing anything. Reported-by: Nadav Amit <nadav.amit@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: x86@kernel.org Link: https://lkml.kernel.org/r/20190307151036.GD26566@zn.tnic |
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