79907146fb
The idea of the overflow-arith.h header is to collect overflow checking functions in one central place. If gcc compiler supports the __builtin_overflow_* builtins we use them because they might give better performance, otherwise the code falls back to normal overflow checking functions. The builtin_overflow functions are supported by gcc-5 and clang. The matter of supporting clang is to just provide a corresponding CC_HAVE_BUILTIN_OVERFLOW, because the specific overflow checking builtins don't differ between gcc and clang. I just provide overflow_usub function here as I intend this to get merged into net, more functions will definitely follow as they are needed. Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
19 lines
277 B
C
19 lines
277 B
C
#pragma once
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#include <linux/kernel.h>
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#ifdef CC_HAVE_BUILTIN_OVERFLOW
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#define overflow_usub __builtin_usub_overflow
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#else
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static inline bool overflow_usub(unsigned int a, unsigned int b,
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unsigned int *res)
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{
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*res = a - b;
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return *res > a ? true : false;
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}
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#endif
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