IPO: INTERPROCEDURAL_OPTIMIZATION (LTCG) for Visual Studio

Add IPO support for Visual Studio (which is referred to by VS as
"Link Time Code Generation" and "Whole Program Optimization"), for
VS version >= 10.  This allows CMake/VS users to enable IPO by setting
property `INTERPROCEDURAL_OPTIMIZATION`.

Fixes: #16748

3 files changed, 10 insertions, 2 deletions

diff --git a/Source/cmGlobalVisualStudio10Generator.h b/Source/cmGlobalVisualStudio10Generator.h
index 6eb597c..63e6903 100644
--- a/Source/cmGlobalVisualStudio10Generator.h
+++ b/Source/cmGlobalVisualStudio10Generator.h
@@ -111,6 +111,8 @@ public:
 
   bool FindMakeProgram(cmMakefile* mf) override;
 
+  bool IsIPOSupported() const override { return true; }
+
   static std::string GetInstalledNsightTegraVersion();
 
   cmIDEFlagTable const* GetClFlagTable() const;
diff --git a/Source/cmVisualStudio10TargetGenerator.cxx b/Source/cmVisualStudio10TargetGenerator.cxx
index 9e74335..c0b0435 100644
--- a/Source/cmVisualStudio10TargetGenerator.cxx
+++ b/Source/cmVisualStudio10TargetGenerator.cxx
@@ -1122,6 +1122,9 @@ void cmVisualStudio10TargetGenerator::WriteMSToolConfigurationValues(
       this->GeneratorTarget->GetPropertyAsBool("VS_WINRT_EXTENSIONS")) {
     e1.Element("WindowsAppContainer", "true");
   }
+  if (this->IPOEnabledConfigurations.count(config) > 0) {
+    e1.Element("WholeProgramOptimization", "true");
+  }
 }
 
 void cmVisualStudio10TargetGenerator::WriteMSToolConfigurationValuesManaged(
@@ -2485,8 +2488,10 @@ bool cmVisualStudio10TargetGenerator::ComputeClOptions(
     clOptions.AddFlag("CompileAs", "CompileAsCpp");
   }
 
-  // Check IPO related warning/error.
-  this->GeneratorTarget->IsIPOEnabled(linkLanguage, configName);
+  // Put the IPO enabled configurations into a set.
+  if (this->GeneratorTarget->IsIPOEnabled(linkLanguage, configName)) {
+    this->IPOEnabledConfigurations.insert(configName);
+  }
 
   // Get preprocessor definitions for this directory.
   std::string defineFlags = this->Makefile->GetDefineFlags();
diff --git a/Source/cmVisualStudio10TargetGenerator.h b/Source/cmVisualStudio10TargetGenerator.h
index 15e47b4..829d2bf 100644
--- a/Source/cmVisualStudio10TargetGenerator.h
+++ b/Source/cmVisualStudio10TargetGenerator.h
@@ -204,6 +204,7 @@ private:
   bool NsightTegra;
   unsigned int NsightTegraVersion[4];
   bool TargetCompileAsWinRT;
+  std::set<std::string> IPOEnabledConfigurations;
   cmGlobalVisualStudio10Generator* const GlobalGenerator;
   cmLocalVisualStudio10Generator* const LocalGenerator;
   std::set<std::string> CSharpCustomCommandNames;