Messages in this thread | | | Date | Tue, 26 May 2020 23:36:01 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH -tip v3 09/11] data_race: Avoid nested statement expression |
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On Tue, May 26, 2020 at 07:33:12PM +0200, Marco Elver wrote: > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > index 5faf68eae204..a529fa263906 100644 > --- a/include/linux/compiler_types.h > +++ b/include/linux/compiler_types.h > @@ -245,7 +245,9 @@ struct ftrace_likely_data { > /* > * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving > * non-scalar types unchanged. > - * > + */ > +#if defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 40900 > +/* > * We build this out of a couple of helper macros in a vain attempt to > * help you keep your lunch down while reading it. > */ > @@ -267,6 +269,24 @@ struct ftrace_likely_data { > __pick_integer_type(x, int, \ > __pick_integer_type(x, long, \ > __pick_integer_type(x, long long, x)))))) > +#else > +/* > + * If supported, prefer C11 _Generic for better compile-times. As above, 'char' > + * is not type-compatible with 'signed char', and we define a separate case. > + */ > +#define __scalar_type_to_expr_cases(type) \ > + type: (type)0, unsigned type: (unsigned type)0 > + > +#define __unqual_scalar_typeof(x) typeof( \ > + _Generic((x), \ > + __scalar_type_to_expr_cases(char), \ > + signed char: (signed char)0, \ > + __scalar_type_to_expr_cases(short), \ > + __scalar_type_to_expr_cases(int), \ > + __scalar_type_to_expr_cases(long), \ > + __scalar_type_to_expr_cases(long long), \ > + default: (x))) > +#endif > > /* Is this type a native word size -- useful for atomic operations */ > #define __native_word(t) \ >
Yeah, this shaves around 5% off of my kernel builds. The _Atomic hack is every so slightly faster on GCC but apparently doesn't work on clang -- also, it's disguisting :-)
Ack!
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