[llvm] 48c74bb - [SampleProfileInference] Work around odr-use of const non-inline static data member to fix -O0 builds after D120508

[David Blaikie via llvm-commits]

On Mon, Jun 27, 2022, 9:23 PM Fangrui Song <i at maskray.me> wrote:

> On Mon, Jun 27, 2022 at 6:01 PM David Blaikie <dblaikie at gmail.com> wrote:
> >
> > Sorry, didn't see this earlier, but came across it looking at a
> > similar change recently - could you add a definition of this instead
> > of a cast, so it's not a trip-hazard for future development?
>
> Do you mean something like D.6 Redeclaration of static constexpr data
> members [depr.static.constexpr] ?
> The usage is deprecated from C++17 onwards.
>

Yep, that. So long as we're building in C++14 mode that's the suitable
thing to do. In 17 onwards we can remove them without them being a trap for
new code to trip over like this.


> >
> > On Tue, Mar 8, 2022 at 2:35 PM Fangrui Song via llvm-commits
> > <llvm-commits at lists.llvm.org> wrote:
> > >
> > >
> > > Author: Fangrui Song
> > > Date: 2022-03-08T14:34:53-08:00
> > > New Revision: 48c74bb2e2a72830f1068823bfc2f6fd4b53d427
> > >
> > > URL:
> https://github.com/llvm/llvm-project/commit/48c74bb2e2a72830f1068823bfc2f6fd4b53d427
> > > DIFF:
> https://github.com/llvm/llvm-project/commit/48c74bb2e2a72830f1068823bfc2f6fd4b53d427.diff
> > >
> > > LOG: [SampleProfileInference] Work around odr-use of const non-inline
> static data member to fix -O0 builds after D120508
> > >
> > > MinBaseDistance may be odr-used by std::max, leading to an undefined
> symbol linker error:
> > >
> > > ```
> > > ld.lld: error: undefined symbol: (anonymous
> namespace)::MinCostMaxFlow::MinBaseDistance
> > > >>> referenced by SampleProfileInference.cpp:744
> (/home/ray/llvm-project/llvm/lib/Transforms/Utils/SampleProfileInference.cpp:744)
> > > >>>
>  lib/Transforms/Utils/CMakeFiles/LLVMTransformUtils.dir/SampleProfileInference.cpp.o:((anonymous
> namespace)::FlowAdjuster::jumpDistance(llvm::FlowJump*) const)
> > > ```
> > >
> > > Since llvm-project is still using C++ 14, workaround it with a cast.
> > >
> > > Added:
> > >
> > >
> > > Modified:
> > >     llvm/lib/Transforms/Utils/SampleProfileInference.cpp
> > >
> > > Removed:
> > >
> > >
> > >
> > >
> ################################################################################
> > > diff  --git a/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
> b/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
> > > index 298c36b7ecd3d..6f56f1c432c2e 100644
> > > --- a/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
> > > +++ b/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
> > > @@ -741,7 +741,7 @@ class FlowAdjuster {
> > >    /// parts to a multiple of 1 / BaseDistance.
> > >    int64_t jumpDistance(FlowJump *Jump) const {
> > >      uint64_t BaseDistance =
> > > -        std::max(MinCostMaxFlow::MinBaseDistance,
> > > +
> std::max(static_cast<uint64_t>(MinCostMaxFlow::MinBaseDistance),
> > >                   std::min(Func.Blocks[Func.Entry].Flow,
> > >                            MinCostMaxFlow::AuxCostUnlikely /
> NumBlocks()));
> > >      if (Jump->IsUnlikely)
> > >
> > >
> > >
> > > _______________________________________________
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> > > llvm-commits at lists.llvm.org
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>
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