Re: [musl] [PATCH] build: allow forcing generic implementations of library functions

[Yuval Deutscher <yuval.d@nextsilicon.com>]

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Hey,

The main goal is to provide an option to disable exactly those optional
optimizations you mentioned. I wrote this patch as I needed their
unoptimized versions as part of a more complex system, and thought it makes
sense to get it merged as it might be useful, since optimizations usually
have a way to be disabled at build time.

You are correct that the current way this is written is too prone to
errors. Maybe we should implement it as a boolean argument that disables
only those optimizations we know are optional? If this makes sense to you,
let me know how exactly do you see it so that I can write a new patch.

On Tue, Jun 16, 2020 at 8:55 PM Rich Felker <dalias@libc.org> wrote:

> On Tue, Jun 16, 2020 at 08:22:23PM +0300, Yuval Deutscher wrote:
> > This change allows excluding chosen functions from ARCH_OBJS thus
> > causing the library to be built with non-platform-specific versions of
> > them. The option can be used by setting the FORCE_GENERIC variable when
> > invoking make.
> >
> > Signed-off-by: Yuval Deutscher <yuval.d@nextsilicon.com>
> > ---
> >  Makefile | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/Makefile b/Makefile
> > index bd8f5c38..c6e5a386 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -23,7 +23,8 @@ ARCH_GLOBS = $(addsuffix /$(ARCH)/*.[csS],$(SRC_DIRS))
> >  BASE_SRCS = $(sort $(wildcard $(BASE_GLOBS)))
> >  ARCH_SRCS = $(sort $(wildcard $(ARCH_GLOBS)))
> >  BASE_OBJS = $(patsubst $(srcdir)/%,%.o,$(basename $(BASE_SRCS)))
> > -ARCH_OBJS = $(patsubst $(srcdir)/%,%.o,$(basename $(ARCH_SRCS)))
> > +ALL_ARCH_OBJS = $(patsubst $(srcdir)/%,%.o,$(basename $(ARCH_SRCS)))
> > +ARCH_OBJS = $(filter-out $(addprefix %/,$(addsuffix
> .o,$(FORCE_GENERIC))), $(ALL_ARCH_OBJS))
> >  REPLACED_OBJS = $(sort $(subst /$(ARCH)/,/,$(ARCH_OBJS)))
> >  ALL_OBJS = $(addprefix obj/, $(filter-out $(REPLACED_OBJS), $(sort
> $(BASE_OBJS) $(ARCH_OBJS))))
> >
> > --
> > 2.25.1
>
> Can you clarify what problem this is attempting to solve? Maybe it
> could be solved better in a different way. As written, this patch
> creates an option that produces broken builds unless you follow
> unwritten rules about which files are valid to include in
> FORCE_GENERIC. Only a very small portion of the ARCH_OBJS (mainly
> string and math) are optional optimizations rather than hard
> requirements.
>
> Rich
>


-- 
Yuval Deutscher

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