diff --git a/lld/COFF/LTO.cpp b/lld/COFF/LTO.cpp
--- a/lld/COFF/LTO.cpp
+++ b/lld/COFF/LTO.cpp
@@ -223,7 +223,7 @@
       continue;
 
     if (config->saveTemps)
-      saveBuffer(buf[i], ltoObjName);
+      saveBuffer(objBuf, ltoObjName);
     ret.push_back(make<ObjFile>(MemoryBufferRef(objBuf, ltoObjName)));
   }
 
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -34,6 +34,7 @@
 #include "llvm/LTO/SummaryBasedOptimizations.h"
 #include "llvm/Linker/IRMover.h"
 #include "llvm/Object/IRObjectFile.h"
+#include "llvm/ProfileData/InstrProf.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
@@ -847,6 +848,15 @@
     M.setModuleInlineAsm(NewIA + M.getModuleInlineAsm());
   }
 
+  // Since IRPGO flag symbol (__llvm_profile_raw_version) has external linkage,
+  // it may not be kept if it's not prevailing in a mixed-LTO mode (both regular
+  // and thin LTO modules) compilation. This symbol will be used in later PGO
+  // Instrumentation phase by isIRPGOFlagSet. Keep this symbol will cause a
+  // duplicate symbol error on ELF. Try set the Module flag beforehand that can
+  // be evaluated later through enablesValueProfiling in PGO pass.
+  if (isIRPGOFlagSet(&M))
+    M.addModuleFlag(llvm::Module::Warning, "EnableValueProfiling", 1);
+
   assert(MsymI == MsymE);
   return std::move(Mod);
 }
@@ -1216,6 +1226,15 @@
       if (!MOrErr)
         return MOrErr.takeError();
 
+      // The IRPGO flag var (__llvm_profile_raw_version) may not be imported if
+      // it's not prevailing and no use in thinLTO module. However this symbol
+      // will be accessed later in PGO Instrumentation phase by isIRPGOFlagSet.
+      // Try set the Module flag instead that can be evaluated later through
+      // enablesValueProfiling in the PGO pass.
+      Module &M = **MOrErr;
+      if (isIRPGOFlagSet(&M))
+        M.addModuleFlag(llvm::Module::Warning, "EnableValueProfiling", 1);
+
       return thinBackend(Conf, Task, AddStream, **MOrErr, CombinedIndex,
                          ImportList, DefinedGlobals, &ModuleMap);
     };
diff --git a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -757,13 +757,28 @@
   CoverageNamesVar->eraseFromParent();
 }
 
+static uint64_t getIntModuleFlagOrZero(const Module &M, StringRef Flag) {
+  auto *MD = dyn_cast_or_null<ConstantAsMetadata>(M.getModuleFlag(Flag));
+  if (!MD)
+    return 0;
+
+  // If the flag is a ConstantAsMetadata, it should be an integer representable
+  // in 64-bits.
+  return cast<ConstantInt>(MD->getValue())->getZExtValue();
+}
+
+static bool enablesValueProfiling(const Module &M) {
+  return getIntModuleFlagOrZero(M, "EnableValueProfiling") != 0 ||
+         isIRPGOFlagSet(&M);
+}
+
 /// Get the name of a profiling variable for a particular function.
 static std::string getVarName(InstrProfIncrementInst *Inc, StringRef Prefix) {
   StringRef NamePrefix = getInstrProfNameVarPrefix();
   StringRef Name = Inc->getName()->getName().substr(NamePrefix.size());
   Function *F = Inc->getParent()->getParent();
   Module *M = F->getParent();
-  if (!DoHashBasedCounterSplit || !isIRPGOFlagSet(M) ||
+  if (!DoHashBasedCounterSplit || !enablesValueProfiling(*M) ||
       !canRenameComdatFunc(*F))
     return (Prefix + Name).str();
   uint64_t FuncHash = Inc->getHash()->getZExtValue();
@@ -773,20 +788,6 @@
   return (Prefix + Name + "." + Twine(FuncHash)).str();
 }
 
-static uint64_t getIntModuleFlagOrZero(const Module &M, StringRef Flag) {
-  auto *MD = dyn_cast_or_null<ConstantAsMetadata>(M.getModuleFlag(Flag));
-  if (!MD)
-    return 0;
-
-  // If the flag is a ConstantAsMetadata, it should be an integer representable
-  // in 64-bits.
-  return cast<ConstantInt>(MD->getValue())->getZExtValue();
-}
-
-static bool enablesValueProfiling(const Module &M) {
-  return isIRPGOFlagSet(&M) ||
-         getIntModuleFlagOrZero(M, "EnableValueProfiling") != 0;
-}
 
 // Conservatively returns true if data variables may be referenced by code.
 static bool profDataReferencedByCode(const Module &M) {
diff --git a/llvm/test/Instrumentation/InstrProfiling/comdat.ll b/llvm/test/Instrumentation/InstrProfiling/comdat.ll
--- a/llvm/test/Instrumentation/InstrProfiling/comdat.ll
+++ b/llvm/test/Instrumentation/InstrProfiling/comdat.ll
@@ -10,8 +10,8 @@
 ; RUN: cat %t/main.ll %t/enable.ll > %t1.ll
 ; RUN: opt < %t0.ll -mtriple=x86_64-linux -passes=instrprof -S | FileCheck %s --check-prefixes=ELF
 ; RUN: opt < %t1.ll -mtriple=x86_64-linux -passes=instrprof -S | FileCheck %s --check-prefixes=ELF
-; RUN: opt < %t0.ll -mtriple=x86_64-windows -passes=instrprof -S | FileCheck %s --check-prefixes=COFF
-; RUN: opt < %t1.ll -mtriple=x86_64-windows -passes=instrprof -S | FileCheck %s --check-prefixes=COFF
+; RUN: opt < %t0.ll -mtriple=x86_64-windows -passes=instrprof -S | FileCheck %s --check-prefixes=COFF0
+; RUN: opt < %t1.ll -mtriple=x86_64-windows -passes=instrprof -S | FileCheck %s --check-prefixes=COFF1
 
 ;--- main.ll
 declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
@@ -38,12 +38,14 @@
   ret void
 }
 
-; ELF:   @__profc_foo_extern = linkonce_odr hidden global{{.*}}, section "__llvm_prf_cnts", comdat, align 8
+; ELF0:   @__profc_foo_extern = linkonce_odr hidden global{{.*}}, section "__llvm_prf_cnts", comdat, align 8
+; ELF1:   @__profc_foo_extern.0 = linkonce_odr hidden global{{.*}}, section "__llvm_prf_cnts", comdat, align 8
 ; ELF0:  @__profd_foo_extern = private global{{.*}}, section "__llvm_prf_data", comdat($__profc_foo_extern), align 8
-; ELF1:  @__profd_foo_extern = linkonce_odr hidden global{{.*}}, section "__llvm_prf_data", comdat($__profc_foo_extern), align 8
-; COFF:  @__profc_foo_extern = linkonce_odr hidden global{{.*}}, section ".lprfc$M", comdat, align 8
+; ELF1:  @__profd_foo_extern.0 = linkonce_odr hidden global{{.*}}, section "__llvm_prf_data", comdat($__profc_foo_extern), align 8
+; COFF0:  @__profc_foo_extern = linkonce_odr hidden global{{.*}}, section ".lprfc$M", comdat, align 8
+; COFF1:  @__profc_foo_extern.0 = linkonce_odr hidden global{{.*}}, section ".lprfc$M", comdat, align 8
 ; COFF0: @__profd_foo_extern = private global{{.*}}, section ".lprfd$M", comdat($__profc_foo_extern), align 8
-; COFF1: @__profd_foo_extern = linkonce_odr hidden global{{.*}}, section ".lprfd$M", comdat, align 8
+; COFF1: @__profd_foo_extern.0 = linkonce_odr hidden global{{.*}}, section ".lprfd$M", comdat, align 8
 define available_externally void @foo_extern() {
   call void @llvm.instrprof.increment(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @__profn_foo_extern, i32 0, i32 0), i64 0, i32 1, i32 0)
   ret void
diff --git a/llvm/test/Transforms/PGOProfile/lto_cspgo_gen.ll b/llvm/test/Transforms/PGOProfile/lto_cspgo_gen.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/PGOProfile/lto_cspgo_gen.ll
@@ -0,0 +1,32 @@
+; REQUIRES: x86-registered-target
+
+; RUN: opt -module-summary %s -o %t1.bc
+; RUN: llvm-lto2 run -lto-cspgo-profile-file=alloc -lto-cspgo-gen -save-temps -o %t %t1.bc \
+; RUN:   -r=%t1.bc,f,pl \
+; RUN:   -r=%t1.bc,__llvm_profile_filename,x \
+; RUN:   -r=%t1.bc,__llvm_profile_raw_version,x
+; RUN: llvm-dis %t.0.0.preopt.bc -o - | FileCheck %s --check-prefix=VALUEPROFILE
+
+; VALUEPROFILE: {{.*}} !"EnableValueProfiling", i32 1}
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+$__llvm_profile_filename = comdat any
+$__llvm_profile_raw_version = comdat any
+@__llvm_profile_filename = local_unnamed_addr constant [19 x i8] c"default_%m.profraw\00", comdat
+@__llvm_profile_raw_version = local_unnamed_addr constant i64 216172782113783813, comdat
+
+; Function Attrs: nofree norecurse nosync nounwind readnone uwtable willreturn mustprogress
+define dso_local i32 @f() local_unnamed_addr #0 {
+entry:
+  ret i32 1
+}
+
+attributes #0 = { "target-cpu"="x86-64" }
+
+!llvm.module.flags = !{!0, !1, !2}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 7, !"uwtable", i32 1}
+!2 = !{i32 1, !"ThinLTO", i32 0}
diff --git a/llvm/test/Transforms/PGOProfile/thinlto_cspgo_gen.ll b/llvm/test/Transforms/PGOProfile/thinlto_cspgo_gen.ll
--- a/llvm/test/Transforms/PGOProfile/thinlto_cspgo_gen.ll
+++ b/llvm/test/Transforms/PGOProfile/thinlto_cspgo_gen.ll
@@ -17,6 +17,7 @@
 
 ; CSGEN: @__profc_
 ; CSGEN: @__profd_
+; CSGEN: {{.*}} !"EnableValueProfiling", i32 1}
 
 source_filename = "cspgo.c"
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"