05/08/2020 18:45, Bruce Richardson: > On Wed, Aug 05, 2020 at 05:15:31PM +0200, Thomas Monjalon wrote: > > 05/08/2020 17:07, Bruce Richardson: > > > On Wed, Aug 05, 2020 at 04:57:42PM +0200, Thomas Monjalon wrote: > > > > 05/08/2020 16:21, Bruce Richardson: > > > > > The RTE_MACHINE_CPUFLAGS_* macros in DPDK build just duplicate info > > > > > from > > > > > the compiler macros, so we can remove them and just use the compiler > > > > > versions directly. > > > > > > > > > > Signed-off-by: Bruce Richardson <bruce.richard...@intel.com> > > > > > --- > > > > > --- a/doc/guides/rel_notes/deprecation.rst > > > > > +++ b/doc/guides/rel_notes/deprecation.rst > > > > > +* build macros: The macros defining RTE_MACHINE_CPUFLAG_* will be > > > > > removed > > > > > + from the build. The information provided by these macros is > > > > > available > > > > > + through standard compiler macros. For example, > > > > > RTE_MACHINE_CPUFLAG_SSE3 > > > > > + duplicates the compiler-provided macro __SSE3__. > > > > > > > > I see 2 advantages of having alias: > > > > - if 2 compilers differ, we can manage > > > > - we can find all such macros with grep RTE_MACHINE_CPUFLAG > > > > > > > > > > Sure, if you think it's worthwhile keeping them, we can do so. It's just > > > right now they seem to be largely a waste of space. For #2, I'm not sure > > > when we would want to grep for them all, except possibly to remove them. > > > :-) > > > > For instance, in a lib, I grep where we have CPU specific code. > > > > We probably need more opinions, I can change my mind. > > > Yes, we need some more opinions here. > > For the above point, yes it's useful to be able to grep for these things, > but it does assume that everybody uses the DPDK-defines and doesn't use the > compiler ones directly. There are a few instances where there seems to be > x86, ARM or PPC compiler flags already directly used in the code. > > As well as brevity, the other big reason I see for removing them is to > avoid having to maintain these lists of flags for future use. Right now, > with -march=skylake-avx512, gcc will define 7 different AVX feature flags. > DPDK, on the other hand, only provides equivalent defines for 3 of them. > We have no automatic way of pulling all newly added flags from gcc/clang > into our build, so we just add them on an as-needed basis, which makes it > more awkward for those adding new features that may depend on the flags. If > we always try to add in all flags to keep things in sync, we are just > duplicating the efforts the compiler authors have already done for us, and > wasting the effort for those flags that are unused.
You see, you can provide good arguments :) Maybe some of them deserve to be part of the patch. Acked-by: Thomas Monjalon <tho...@monjalon.net>
