3 files changed, 10 insertions, 1 deletions
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 55d631733ad..198b0b5b228 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5395,7 +5395,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back("-fwhole-program-vtables");
   }
 
-  bool DefaultsSplitLTOUnit = WholeProgramVTables || Sanitize.needsLTO();
+  bool DefaultsSplitLTOUnit =
+      (WholeProgramVTables || Sanitize.needsLTO()) &&
+      (D.getLTOMode() == LTOK_Full || TC.canSplitThinLTOUnit());
   bool SplitLTOUnit =
       Args.hasFlag(options::OPT_fsplit_lto_unit,
                    options::OPT_fno_split_lto_unit, DefaultsSplitLTOUnit);
diff --git a/clang/lib/Driver/ToolChains/Darwin.h b/clang/lib/Driver/ToolChains/Darwin.h
index 2dc7c85880f..1b1c358c40a 100644
--- a/clang/lib/Driver/ToolChains/Darwin.h
+++ b/clang/lib/Driver/ToolChains/Darwin.h
@@ -258,6 +258,9 @@ public:
     return "";
   }
 
+  // Darwin toolchain uses legacy thin LTO API, which is not
+  // capable of unit splitting.
+  bool canSplitThinLTOUnit() const override { return false; }
   /// }
 };
 
diff --git a/clang/lib/Driver/ToolChains/PS4CPU.h b/clang/lib/Driver/ToolChains/PS4CPU.h
index e9f0891c119..18852b2808c 100644
--- a/clang/lib/Driver/ToolChains/PS4CPU.h
+++ b/clang/lib/Driver/ToolChains/PS4CPU.h
@@ -84,6 +84,10 @@ public:
 
   SanitizerMask getSupportedSanitizers() const override;
 
+  // PS4 toolchain uses legacy thin LTO API, which is not
+  // capable of unit splitting.
+  bool canSplitThinLTOUnit() const override { return false; }
+
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;