[PATCH] D40697: Cache modulo values for the .gnu.hash section.

[Rui Ueyama via llvm-commits]

On Fri, Dec 1, 2017 at 2:08 PM, Rafael Avila de Espindola <
rafael.espindola at gmail.com> wrote:

> Rui Ueyama <ruiu at google.com> writes:
>
> > On Fri, Dec 1, 2017 at 1:41 PM, Rafael Avila de Espindola <
> > rafael.espindola at gmail.com> wrote:
> >
> >> Rui Ueyama via Phabricator <reviews at reviews.llvm.org> writes:
> >>
> >> > ruiu updated this revision to Diff 125067.
> >> > ruiu added a comment.
> >> >
> >> > - clang-format
> >> >
> >> > It seems this patch actually makes that test case 2% faster, which
> >> > isn't a negligible improvement.
> >>
> >> Please benchmark more than clang. There is a set of different benchmarks
> >> in https://s3-us-west-2.amazonaws.com/linker-tests/
> lld-speed-test.tar.xz.
> >>
> >>
> >> >    // Write hash buckets. Hash buckets contain indices in the
> following
> >> >    // hash value table.
> >> > @@ -1792,21 +1792,22 @@
> >> >    if (Mid == V.end())
> >> >      return;
> >> >
> >> > -  for (SymbolTableEntry &Ent : llvm::make_range(Mid, V.end())) {
> >> > -    Symbol *B = Ent.Sym;
> >> > -    Symbols.push_back({B, Ent.StrTabOffset, hashGnu(B->getName())});
> >> > -  }
> >> > -
> >>
> >> I would leave something like
> >>
> >> auto HashedSyms = llvm::make_range(Mid, V.end();
> >>
> >>
> >> >    // We chose load factor 4 for the on-disk hash table. For each hash
> >> >    // collision, the dynamic linker will compare a uint32_t hash
> value.
> >> >    // Since the integer comparison is quite fast, we believe we can
> make
> >> >    // the load factor even larger. 4 is just a conservative choice.
> >> > -  NBuckets = std::max<size_t>(Symbols.size() / 4, 1);
> >> > +  NBuckets = std::max<size_t>((V.end() - Mid) / 4, 1);
> >>
> >> And use it here.
> >
> >
> > llvm::range doesn't have `size()`, so you can't use it here.
>
> You can use end() - begin(), no?
>

I tried that but it didn't look beautiful, so I'd keep it as is .
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