[PATCH] D42528: [LTO] - Introduce GlobalResolution::Prevailing flag.

[Rafael Avila de Espindola via llvm-commits]

LGTM with the comment Teresa suggested added.

Thanks,
Rafael

George Rimar via Phabricator <reviews at reviews.llvm.org> writes:

> grimar updated this revision to Diff 131450.
> grimar added a comment.
>
> - Addressed review comment.
>
>
> https://reviews.llvm.org/D42528
>
> Files:
>   include/llvm/LTO/LTO.h
>   lib/LTO/LTO.cpp
>
>
> Index: lib/LTO/LTO.cpp
> ===================================================================
> --- lib/LTO/LTO.cpp
> +++ lib/LTO/LTO.cpp
> @@ -419,8 +419,9 @@
>      auto &GlobalRes = GlobalResolutions[Sym.getName()];
>      GlobalRes.UnnamedAddr &= Sym.isUnnamedAddr();
>      if (Res.Prevailing) {
> -      assert(GlobalRes.IRName.empty() &&
> +      assert(!GlobalRes.Prevailing &&
>               "Multiple prevailing defs are not allowed");
> +      GlobalRes.Prevailing = true;
>        GlobalRes.IRName = Sym.getIRName();
>      }
>  
> @@ -746,14 +747,10 @@
>  Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
>    // Compute "dead" symbols, we don't want to import/export these!
>    DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
> -  for (auto &Res : GlobalResolutions) {
> -    if (Res.second.VisibleOutsideSummary &&
> -        // IRName will be defined if we have seen the prevailing copy of
> -        // this value. If not, no need to preserve any ThinLTO copies.
> -        !Res.second.IRName.empty())
> +  for (auto &Res : GlobalResolutions)
> +    if (Res.second.VisibleOutsideSummary && Res.second.Prevailing)
>        GUIDPreservedSymbols.insert(GlobalValue::getGUID(
>            GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
> -  }
>  
>    computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
>  
> @@ -803,7 +800,7 @@
>  
>    if (!Conf.CodeGenOnly) {
>      for (const auto &R : GlobalResolutions) {
> -      if (R.second.IRName.empty())
> +      if (!R.second.Prevailing)
>          continue;
>        if (R.second.Partition != 0 &&
>            R.second.Partition != GlobalResolution::External)
> @@ -1114,13 +1111,10 @@
>    // undefined references during the final link.
>    std::set<GlobalValue::GUID> ExportedGUIDs;
>    for (auto &Res : GlobalResolutions) {
> -    // First check if the symbol was flagged as having external references.
> -    if (Res.second.Partition != GlobalResolution::External)
> -      continue;
> -    // IRName will be defined if we have seen the prevailing copy of
> -    // this value. If not, no need to mark as exported from a ThinLTO
> -    // partition (and we can't get the GUID).
> -    if (Res.second.IRName.empty())
> +    // If the symbol does not have external references or it is not prevailing,
> +    // then not need to mark it as exported from a ThinLTO partition.
> +    if (Res.second.Partition != GlobalResolution::External ||
> +        !Res.second.Prevailing)
>        continue;
>      auto GUID = GlobalValue::getGUID(
>          GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
> Index: include/llvm/LTO/LTO.h
> ===================================================================
> --- include/llvm/LTO/LTO.h
> +++ include/llvm/LTO/LTO.h
> @@ -320,6 +320,8 @@
>  
>      bool UnnamedAddr = true;
>  
> +    bool Prevailing = false;
> +
>      /// This field keeps track of the partition number of this global. The
>      /// regular LTO object is partition 0, while each ThinLTO object has its own
>      /// partition number from 1 onwards.
>
>
> Index: lib/LTO/LTO.cpp
> ===================================================================
> --- lib/LTO/LTO.cpp
> +++ lib/LTO/LTO.cpp
> @@ -419,8 +419,9 @@
>      auto &GlobalRes = GlobalResolutions[Sym.getName()];
>      GlobalRes.UnnamedAddr &= Sym.isUnnamedAddr();
>      if (Res.Prevailing) {
> -      assert(GlobalRes.IRName.empty() &&
> +      assert(!GlobalRes.Prevailing &&
>               "Multiple prevailing defs are not allowed");
> +      GlobalRes.Prevailing = true;
>        GlobalRes.IRName = Sym.getIRName();
>      }
>  
> @@ -746,14 +747,10 @@
>  Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
>    // Compute "dead" symbols, we don't want to import/export these!
>    DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
> -  for (auto &Res : GlobalResolutions) {
> -    if (Res.second.VisibleOutsideSummary &&
> -        // IRName will be defined if we have seen the prevailing copy of
> -        // this value. If not, no need to preserve any ThinLTO copies.
> -        !Res.second.IRName.empty())
> +  for (auto &Res : GlobalResolutions)
> +    if (Res.second.VisibleOutsideSummary && Res.second.Prevailing)
>        GUIDPreservedSymbols.insert(GlobalValue::getGUID(
>            GlobalValue::dropLLVMManglingEscape(Res.second.IRName)));
> -  }
>  
>    computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols);
>  
> @@ -803,7 +800,7 @@
>  
>    if (!Conf.CodeGenOnly) {
>      for (const auto &R : GlobalResolutions) {
> -      if (R.second.IRName.empty())
> +      if (!R.second.Prevailing)
>          continue;
>        if (R.second.Partition != 0 &&
>            R.second.Partition != GlobalResolution::External)
> @@ -1114,13 +1111,10 @@
>    // undefined references during the final link.
>    std::set<GlobalValue::GUID> ExportedGUIDs;
>    for (auto &Res : GlobalResolutions) {
> -    // First check if the symbol was flagged as having external references.
> -    if (Res.second.Partition != GlobalResolution::External)
> -      continue;
> -    // IRName will be defined if we have seen the prevailing copy of
> -    // this value. If not, no need to mark as exported from a ThinLTO
> -    // partition (and we can't get the GUID).
> -    if (Res.second.IRName.empty())
> +    // If the symbol does not have external references or it is not prevailing,
> +    // then not need to mark it as exported from a ThinLTO partition.
> +    if (Res.second.Partition != GlobalResolution::External ||
> +        !Res.second.Prevailing)
>        continue;
>      auto GUID = GlobalValue::getGUID(
>          GlobalValue::dropLLVMManglingEscape(Res.second.IRName));
> Index: include/llvm/LTO/LTO.h
> ===================================================================
> --- include/llvm/LTO/LTO.h
> +++ include/llvm/LTO/LTO.h
> @@ -320,6 +320,8 @@
>  
>      bool UnnamedAddr = true;
>  
> +    bool Prevailing = false;
> +
>      /// This field keeps track of the partition number of this global. The
>      /// regular LTO object is partition 0, while each ThinLTO object has its own
>      /// partition number from 1 onwards.