[llvm] r284069 - [unittests] Delete even more copy constructors (NFC)

[David Blaikie via llvm-commits]

On Mon, Oct 17, 2016 at 11:02 AM Vedant Kumar <vsk at apple.com> wrote:

> While we didn't have any cases where we'd copy InputFunctionCoverageData
> objects, I wanted to prevent these copies from ever occurring because they
> would be expensive. Each object contains a SmallDenseMap<unsigned,
> unsigned>
> and a std::vector<CounterMappingRegion>.
>
> This commit was motivated by a case where we called std::vector::resize on
> a
> vector of OutputFunctionCoverageData. Deleting the copy constructor in that
> case should have made the resize operation cheaper (caveat - I haven't
> actually
> measured this).
>

If the move ctor/assign is noexcept, it should be OK as-is (without
removing the copy ops). We (C++/Clang/etc) don't really have a good answer
for this in a codebase without exceptions anyway... :/

This is pretty far outside any of the code I deal with, so do whatever
works best for you, but I'd probably avoid the extra complexity & leaev the
code as it was before.

- Dave


>
> vedant
>
> > On Oct 17, 2016, at 9:58 AM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> > Were these copies problematic in any way? If it's just a POD type, you
> might as well leave it copyable, etc?
> >
> > On Wed, Oct 12, 2016 at 3:53 PM Vedant Kumar via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
> > Author: vedantk
> > Date: Wed Oct 12 17:44:50 2016
> > New Revision: 284069
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=284069&view=rev
> > Log:
> > [unittests] Delete even more copy constructors (NFC)
> >
> > Modified:
> >     llvm/trunk/unittests/ProfileData/CoverageMappingTest.cpp
> >
> > Modified: llvm/trunk/unittests/ProfileData/CoverageMappingTest.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ProfileData/CoverageMappingTest.cpp?rev=284069&r1=284068&r2=284069&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/unittests/ProfileData/CoverageMappingTest.cpp (original)
> > +++ llvm/trunk/unittests/ProfileData/CoverageMappingTest.cpp Wed Oct 12
> 17:44:50 2016
> > @@ -106,6 +106,16 @@ struct InputFunctionCoverageData {
> >
> >    InputFunctionCoverageData(std::string Name, uint64_t Hash)
> >        : Name(std::move(Name)), Hash(Hash) {}
> > +
> > +  InputFunctionCoverageData(InputFunctionCoverageData &&IFCD)
> > +      :
> ReverseVirtualFileMapping(std::move(IFCD.ReverseVirtualFileMapping)),
> > +        Name(std::move(IFCD.Name)), Hash(IFCD.Hash),
> > +        Regions(std::move(IFCD.Regions)) {}
> > +
> > +  InputFunctionCoverageData(const InputFunctionCoverageData &) = delete;
> > +  InputFunctionCoverageData &
> > +  operator=(const InputFunctionCoverageData &) = delete;
> > +  InputFunctionCoverageData &operator=(InputFunctionCoverageData &&) =
> delete;
> >  };
> >
> >  struct CoverageMappingTest : ::testing::Test {
> >
> >
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>
>
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