[PATCH] D14547: [llvm-profdata] Add support for weighted merge of profile data

[Xinliang David Li via llvm-commits]

We can simply document it. In other words, user is not expected  to use
":<num>" or ",<num>" as file suffix for profile data.

David

On Wed, Nov 11, 2015 at 1:45 PM, Justin Bogner <mail at justinbogner.com>
wrote:

> Xinliang David Li <davidxl at google.com> writes:
> > On Tue, Nov 10, 2015 at 2:36 PM, Diego Novillo <dnovillo at google.com>
> wrote:
> >> On Tue, Nov 10, 2015 at 3:07 PM, David Li <davidxl at google.com> wrote:
> >>> ================
> >>> Comment at: test/tools/llvm-profdata/weight-sample.test:42
> >>> @@ +41,3 @@
> >>> +3- Bad merge: foo and bar profiles with too few weight values
> >>> +RUN: not llvm-profdata merge --sample --text -weights=2
> >>> %p/Inputs/weight-sample-bar.proftext
> %p/Inputs/weight-sample-foo.proftext
> >>> -o %t.out 2>&1 | FileCheck %s --check-prefix=ERROR1
> >>> +ERROR1: error: Profile weight must be specified for each input file.
> >>> ----------------
> >>> No need for such tests if the weight is always attached to the input
> file.
> >>>
> >>
> >> But then what happens if one of the files is specified without
> ":WEIGHT"?
> >> Should we complain about it?  Should we assume MAX(other weights)?
> >
> > The default is 1 of course.
> >
> >> I'm not sure I'm completely convinced that file1:W1 file2:W2 is better
> >> than --weights=W1,W2.  What if ':' is part of the filename?  I know,
> seems
> >> like a stretch.  I'm not actually arguing against it.  I mostly find it
> a
> >> bit odd.
> >
> > : is just a suggestion, you can use coma to separate it.
> >
> > pros:
> >
> > 1) the weight and file name are always 'together'. Think about a long
> list
> > of files -- having a separate list option make it harder to associate and
> > and  can not really skip the default weight of 1, e.g
> > -W10,1,1,1,1,1,1,1,1,1,20
> > 2) there is no need for an additional option
> > 3) the implementation is simpler and requires fewer code.
> >
> > cons:
> > I don't see any real cons -- except that you find it weird -- but why?
>
> The biggest con is probably ambiguity. Using a comma isn't really any
> better than using a colon here, both are perfectly valid in filenames.
> I guess it's probably not likely that anyone has a file named foo and a
> file named foo:10 and wants to use foo with a weight of 10, but the code
> will certainly have to deal with that case if we're attaching the
> weights to the filenames.
>
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