Add policy CMP0069 to enforce INTERPROCEDURAL_OPTIMIZATION

Previously the `INTERPROCEDURAL_OPTIMIZATION` target property was
honored only for the Intel compiler on Linux and otherwise ignored.  In
order to add support for more compilers incrementally without changing
behavior in the future, add a new policy whose NEW behavior enforces the
`INTERPROCEDURAL_OPTIMIZATION` property.  Add flags for supported
compilers and otherwise produce an error.

9 files changed, 78 insertions, 2 deletions

diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 2199e4a..bb79050 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -286,6 +286,7 @@ cmGeneratorTarget::cmGeneratorTarget(cmTarget* t, cmLocalGenerator* lg)
   , FortranModuleDirectoryCreated(false)
   , SourceFileFlagsConstructed(false)
   , PolicyWarnedCMP0022(false)
+  , PolicyReportedCMP0069(false)
   , DebugIncludesDone(false)
   , DebugCompileOptionsDone(false)
   , DebugCompileFeaturesDone(false)
@@ -659,7 +660,62 @@ const char* cmGeneratorTarget::GetFeature(const std::string& feature,
 bool cmGeneratorTarget::IsIPOEnabled(const std::string& config) const
 {
   const char* feature = "INTERPROCEDURAL_OPTIMIZATION";
-  return cmSystemTools::IsOn(this->GetFeature(feature, config));
+  const bool result = cmSystemTools::IsOn(this->GetFeature(feature, config));
+
+  if (!result) {
+    // 'INTERPROCEDURAL_OPTIMIZATION' is off, no need to check policies
+    return false;
+  }
+
+  cmPolicies::PolicyStatus cmp0069 = this->GetPolicyStatusCMP0069();
+
+  if (cmp0069 == cmPolicies::OLD || cmp0069 == cmPolicies::WARN) {
+    if (this->Makefile->IsOn("_CMAKE_IPO_LEGACY_BEHAVIOR")) {
+      return true;
+    }
+    if (this->PolicyReportedCMP0069) {
+      // problem is already reported, no need to issue a message
+      return false;
+    }
+    if (cmp0069 == cmPolicies::WARN) {
+      std::ostringstream w;
+      w << cmPolicies::GetPolicyWarning(cmPolicies::CMP0069) << "\n";
+      w << "INTERPROCEDURAL_OPTIMIZATION property will be ignored for target "
+        << "'" << this->GetName() << "'.";
+      this->LocalGenerator->GetCMakeInstance()->IssueMessage(
+        cmake::AUTHOR_WARNING, w.str(), this->GetBacktrace());
+
+      this->PolicyReportedCMP0069 = true;
+    }
+    return false;
+  }
+
+  // Note: check consistency with messages from CheckIPOSupported
+  const char* message = CM_NULLPTR;
+  if (!this->Makefile->IsOn("_CMAKE_IPO_SUPPORTED_BY_CMAKE")) {
+    message = "CMake doesn't support IPO for current compiler";
+  } else if (!this->Makefile->IsOn(
+               "_CMAKE_IPO_MAY_BE_SUPPORTED_BY_COMPILER")) {
+    message = "Compiler doesn't support IPO";
+  } else if (!this->GlobalGenerator->IsIPOSupported()) {
+    message = "CMake doesn't support IPO for current generator";
+  }
+
+  if (!message) {
+    // No error/warning messages
+    return true;
+  }
+
+  if (this->PolicyReportedCMP0069) {
+    // problem is already reported, no need to issue a message
+    return false;
+  }
+
+  this->PolicyReportedCMP0069 = true;
+
+  this->LocalGenerator->GetCMakeInstance()->IssueMessage(
+    cmake::FATAL_ERROR, message, this->GetBacktrace());
+  return false;
 }
 
 const std::string& cmGeneratorTarget::GetObjectName(cmSourceFile const* file)
diff --git a/Source/cmGeneratorTarget.h b/Source/cmGeneratorTarget.h
index 0ec7389..80bccd5 100644
--- a/Source/cmGeneratorTarget.h
+++ b/Source/cmGeneratorTarget.h
@@ -743,6 +743,7 @@ private:
   mutable std::set<cmLinkItem> UtilityItems;
   cmPolicies::PolicyMap PolicyMap;
   mutable bool PolicyWarnedCMP0022;
+  mutable bool PolicyReportedCMP0069;
   mutable bool DebugIncludesDone;
   mutable bool DebugCompileOptionsDone;
   mutable bool DebugCompileFeaturesDone;
diff --git a/Source/cmGlobalGenerator.h b/Source/cmGlobalGenerator.h
index b3cb41f..6432538 100644
--- a/Source/cmGlobalGenerator.h
+++ b/Source/cmGlobalGenerator.h
@@ -333,6 +333,8 @@ public:
 
   virtual bool UseFolderProperty() const;
 
+  virtual bool IsIPOSupported() const { return false; }
+
   /** Return whether the generator should use EFFECTIVE_PLATFORM_NAME. This is
       relevant for mixed macOS and iOS builds. */
   virtual bool UseEffectivePlatformName(cmMakefile*) const { return false; }
diff --git a/Source/cmGlobalNinjaGenerator.h b/Source/cmGlobalNinjaGenerator.h
index a51e919..956af51 100644
--- a/Source/cmGlobalNinjaGenerator.h
+++ b/Source/cmGlobalNinjaGenerator.h
@@ -99,6 +99,8 @@ public:
    */
   static bool SupportsPlatform() { return false; }
 
+  bool IsIPOSupported() const CM_OVERRIDE { return true; }
+
   /**
    * Write a build statement to @a os with the @a comment using
    * the @a rule the list of @a outputs files and inputs.
diff --git a/Source/cmGlobalUnixMakefileGenerator3.h b/Source/cmGlobalUnixMakefileGenerator3.h
index 67d7bc9..bbf9f0f 100644
--- a/Source/cmGlobalUnixMakefileGenerator3.h
+++ b/Source/cmGlobalUnixMakefileGenerator3.h
@@ -149,6 +149,8 @@ public:
   /** Does the make tool tolerate .DELETE_ON_ERROR? */
   virtual bool AllowDeleteOnError() const { return true; }
 
+  bool IsIPOSupported() const CM_OVERRIDE { return true; }
+
   void ComputeTargetObjectDirectory(cmGeneratorTarget* gt) const CM_OVERRIDE;
 
   std::string IncludeDirective;
diff --git a/Source/cmGlobalXCodeGenerator.cxx b/Source/cmGlobalXCodeGenerator.cxx
index 77f3408..45993ce 100644
--- a/Source/cmGlobalXCodeGenerator.cxx
+++ b/Source/cmGlobalXCodeGenerator.cxx
@@ -1664,6 +1664,9 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
     return;
   }
 
+  // Check IPO related warning/error.
+  gtgt->IsIPOEnabled(configName);
+
   // Add define flags
   this->CurrentLocalGenerator->AppendFlags(
     defFlags, this->CurrentMakefile->GetDefineFlags());
diff --git a/Source/cmLocalVisualStudio7Generator.cxx b/Source/cmLocalVisualStudio7Generator.cxx
index 7c33821..cd5b46b 100644
--- a/Source/cmLocalVisualStudio7Generator.cxx
+++ b/Source/cmLocalVisualStudio7Generator.cxx
@@ -670,6 +670,9 @@ void cmLocalVisualStudio7Generator::WriteConfiguration(
 
     // Add the target-specific flags.
     this->AddCompileOptions(flags, target, linkLanguage, configName);
+
+    // Check IPO related warning/error.
+    target->IsIPOEnabled(configName);
   }
 
   if (this->FortranProject) {
diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index ecf06b3..72dcc4f 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -203,6 +203,9 @@ class cmMakefile;
          3, 8, 0, cmPolicies::WARN)                                           \
   SELECT(POLICY, CMP0068,                                                     \
          "RPATH settings on macOS do not affect install_name.", 3, 9, 0,      \
+         cmPolicies::WARN)                                                    \
+  SELECT(POLICY, CMP0069,                                                     \
+         "INTERPROCEDURAL_OPTIMIZATION is enforced when enabled.", 3, 9, 0,   \
          cmPolicies::WARN)
 
 #define CM_SELECT_ID(F, A1, A2, A3, A4, A5, A6) F(A1)
@@ -225,7 +228,8 @@ class cmMakefile;
   F(CMP0060)                                                                  \
   F(CMP0063)                                                                  \
   F(CMP0065)                                                                  \
-  F(CMP0068)
+  F(CMP0068)                                                                  \
+  F(CMP0069)
 
 /** \class cmPolicies
  * \brief Handles changes in CMake behavior and policies
diff --git a/Source/cmVisualStudio10TargetGenerator.cxx b/Source/cmVisualStudio10TargetGenerator.cxx
index 84767a8..2ab72dc 100644
--- a/Source/cmVisualStudio10TargetGenerator.cxx
+++ b/Source/cmVisualStudio10TargetGenerator.cxx
@@ -2239,6 +2239,9 @@ bool cmVisualStudio10TargetGenerator::ComputeClOptions(
                                             linkLanguage, configName.c_str());
   }
 
+  // Check IPO related warning/error.
+  this->GeneratorTarget->IsIPOEnabled(configName);
+
   // Get preprocessor definitions for this directory.
   std::string defineFlags =
     this->GeneratorTarget->Target->GetMakefile()->GetDefineFlags();