On Mon, Jan 06, 2025 at 12:58:44PM +0100, Morten Brørup wrote: > > From: Bruce Richardson [mailto:bruce.richard...@intel.com] > > Sent: Monday, 6 January 2025 12.34 > > > > On Mon, Jan 06, 2025 at 12:21:39PM +0100, Morten Brørup wrote: > > > > From: Bruce Richardson [mailto:bruce.richard...@intel.com] > > > > Sent: Monday, 6 January 2025 12.07 > > > > > > > > On Fri, Jan 03, 2025 at 12:39:38PM -0800, Andre Muezerie wrote: > > > > > __builtin_add_overflow is gcc specific. There's a need for a > > portable > > > > > version that can also be used with other compilers. > > > > > > > > > > This patch introduces rte_add_overflow. > > > > > > > > > > +/* > > > > > + * Function that allows performing simple arithmetic operations > > > > together with > > > > > + * checking whether the operation overflowed. > > > > > + * Example of usage: > > > > > + * uint8_t overflow; > > > > > + * uint16_t a, b, result; > > > > > + * a = 1; > > > > > + * b = 2; > > > > > + * overflow = rte_add_overflow(a, b, &result); > > > > > + */ > > > > > +#ifdef RTE_TOOLCHAIN_MSVC > > > > > +#define rte_add_overflow(a, b, res) _Generic((a), \ > > > > > + uint8_t : _addcarry_u8, \ > > > > > + uint16_t : _addcarry_u16, \ > > > > > + uint32_t : _addcarry_u32, \ > > > > > + uint64_t : _addcarry_u64)(0, a, b, res) > > > > > +#else > > > > > +#define rte_add_overflow(a, b, res) _Generic((a), \ > > > > > + uint8_t : __builtin_add_overflow, \ > > > > > + uint16_t : __builtin_add_overflow, \ > > > > > + uint32_t : __builtin_add_overflow, \ > > > > > + uint64_t : __builtin_add_overflow)(a, b, res) > > > > > +#endif > > > > > > > > For the gcc version, can you just simplify to the one-line below? > > > > > > > > #define rte_add_overflow __builtin_add_overflow > > > > > > Yes, but then GCC compilation would not fail if "a" has some other > > type than the four types explicitly supported. > > > I prefer keeping the method used this v2 patch. > > > > > Is that really a problem? Should our DPDK macro not support all the > > types > > that the GCC builtin supports? > > The DPDK macro should support all the types that both MSVC and GCC supports. > Using _Generic() for GCC is an improvement for the CI to catch MSVC > incompatible code when building for GCC. > > Only these four unsigned types are supported by the x86_64 intrinsics. > I don't think we need support for more types; but if the need should arise, > it can be added later.
Great. Let me know if any further action is needed on this patch.
