Index: cfe/trunk/test/Profile/cxx-templates.cpp
===================================================================
--- cfe/trunk/test/Profile/cxx-templates.cpp
+++ cfe/trunk/test/Profile/cxx-templates.cpp
@@ -10,8 +10,8 @@
 // RUN: FileCheck --input-file=%tuse -check-prefix=T0USE -check-prefix=ALL %s
 // RUN: FileCheck --input-file=%tuse -check-prefix=T100USE -check-prefix=ALL %s
 
-// T0GEN: @[[T0C:__profc__Z4loopILj0EEvv]] = {{(linkonce_odr hidden|internal)}} global [2 x i64] zeroinitializer
-// T100GEN: @[[T100C:__profc__Z4loopILj100EEvv]] = {{(linkonce_odr hidden|internal)}} global [2 x i64] zeroinitializer
+// T0GEN: @[[T0C:__profc__Z4loopILj0EEvv]] = linkonce_odr {{(hidden|dso_local)}} global [2 x i64] zeroinitializer
+// T100GEN: @[[T100C:__profc__Z4loopILj100EEvv]] = linkonce_odr {{(hidden|dso_local)}} global [2 x i64] zeroinitializer
 
 // T0GEN-LABEL: define linkonce_odr {{.*}}void @_Z4loopILj0EEvv()
 // T0USE-LABEL: define linkonce_odr {{.*}}void @_Z4loopILj0EEvv()
Index: compiler-rt/trunk/test/profile/coverage-inline.cpp
===================================================================
--- compiler-rt/trunk/test/profile/coverage-inline.cpp
+++ compiler-rt/trunk/test/profile/coverage-inline.cpp
@@ -1,11 +1,18 @@
+// Test that the instrumentation puts the right linkage on the profile data for
+// inline functions.
 // RUN: %clang_profgen -g -fcoverage-mapping -c -o %t1.o %s -DOBJECT_1
 // RUN: %clang_profgen -g -fcoverage-mapping -c -o %t2.o %s
 // RUN: %clang_profgen -g -fcoverage-mapping %t1.o %t2.o -o %t.exe
 // RUN: env LLVM_PROFILE_FILE=%t.profraw %run %t.exe
 // RUN: llvm-profdata show %t.profraw -all-functions | FileCheck %s
 
-// Test that the instrumentation puts the right linkage on the profile data for
-// inline functions.
+// Again, with optimizations and inlining. This tests that we use comdats
+// correctly.
+// RUN: %clang_profgen -O2 -g -fcoverage-mapping -c -o %t1.o %s -DOBJECT_1
+// RUN: %clang_profgen -O2 -g -fcoverage-mapping -c -o %t2.o %s
+// RUN: %clang_profgen -g -fcoverage-mapping %t1.o %t2.o -o %t.exe
+// RUN: env LLVM_PROFILE_FILE=%t.profraw %run %t.exe
+// RUN: llvm-profdata show %t.profraw -all-functions | FileCheck %s
 
 // CHECK:  {{.*}}foo{{.*}}:
 // CHECK-NEXT:    Hash:
Index: llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -743,30 +743,23 @@
 
   // Move the name variable to the right section. Place them in a COMDAT group
   // if the associated function is a COMDAT. This will make sure that only one
-  // copy of counters of the COMDAT function will be emitted after linking.
+  // copy of counters of the COMDAT function will be emitted after linking. Keep
+  // in mind that this pass may run before the inliner, so we need to create a
+  // new comdat group for the counters and profiling data. If we use the comdat
+  // of the parent function, that will result in relocations against discarded
+  // sections.
   Comdat *Cmdt = nullptr;
   GlobalValue::LinkageTypes CounterLinkage = Linkage;
   if (needsComdatForCounter(*Fn, *M)) {
+    StringRef CmdtPrefix = getInstrProfComdatPrefix();
     if (TT.isOSBinFormatCOFF()) {
-      // There are two cases that need a comdat on COFF:
-      // 1. Functions that already have comdats (standard case)
-      // 2. available_externally functions (dllimport and C99 inline)
-      // In the first case, put all the data in the original function comdat. In
-      // the second case, create a new comdat group using the counter as the
-      // leader. It's linkage must be external, so use linkonce_odr linkage in
-      // that case.
-      if (Comdat *C = Fn->getComdat()) {
-        Cmdt = C;
-      } else {
-        Cmdt = M->getOrInsertComdat(
-            getVarName(Inc, getInstrProfCountersVarPrefix()));
-        CounterLinkage = GlobalValue::LinkOnceODRLinkage;
-      }
-    } else {
-      // For other platforms that use comdats (ELF), make a new comdat group for
-      // all the profile data. It will be deduplicated within the current DSO.
-      Cmdt = M->getOrInsertComdat(getVarName(Inc, getInstrProfComdatPrefix()));
+      // For COFF, the comdat group name must be the name of a symbol in the
+      // group. Use the counter variable name, and upgrade its linkage to
+      // something externally visible, like linkonce_odr.
+      CmdtPrefix = getInstrProfCountersVarPrefix();
+      CounterLinkage = GlobalValue::LinkOnceODRLinkage;
     }
+    Cmdt = M->getOrInsertComdat(getVarName(Inc, CmdtPrefix));
   }
 
   uint64_t NumCounters = Inc->getNumCounters()->getZExtValue();
Index: llvm/trunk/test/Instrumentation/InstrProfiling/PR23499.ll
===================================================================
--- llvm/trunk/test/Instrumentation/InstrProfiling/PR23499.ll
+++ llvm/trunk/test/Instrumentation/InstrProfiling/PR23499.ll
@@ -20,8 +20,8 @@
 
 
 ; COFF-NOT: __profn__Z3barIvEvv
-; COFF: @__profc__Z3barIvEvv = internal global [1 x i64] zeroinitializer, section "{{.*}}prfc$M", comdat($_Z3barIvEvv), align 8
-; COFF: @__profd__Z3barIvEvv = internal global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8*{{.*}}, i8* null, i32 1, [2 x i16] zeroinitializer }, section "{{.*}}prfd{{.*}}", comdat($_Z3barIvEvv), align 8
+; COFF: @__profc__Z3barIvEvv = linkonce_odr dso_local global [1 x i64] zeroinitializer, section "{{.*}}prfc$M", comdat, align 8
+; COFF: @__profd__Z3barIvEvv = internal global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8*{{.*}}, i8* null, i32 1, [2 x i16] zeroinitializer }, section "{{.*}}prfd{{.*}}", comdat($__profc__Z3barIvEvv), align 8
 
 
 declare void @llvm.instrprof.increment(i8*, i64, i32, i32) #1
Index: llvm/trunk/test/Instrumentation/InstrProfiling/comdat.ll
===================================================================
--- llvm/trunk/test/Instrumentation/InstrProfiling/comdat.ll
+++ llvm/trunk/test/Instrumentation/InstrProfiling/comdat.ll
@@ -17,8 +17,8 @@
 
 ; ELF: @__profc_foo_inline = linkonce_odr hidden global{{.*}}, section "__llvm_prf_cnts", comdat($__profv_foo_inline), align 8
 ; ELF: @__profd_foo_inline = linkonce_odr hidden global{{.*}}, section "__llvm_prf_data", comdat($__profv_foo_inline), align 8
-; COFF: @__profc_foo_inline = internal global{{.*}}, section ".lprfc$M", comdat($foo_inline), align 8
-; COFF: @__profd_foo_inline = internal global{{.*}}, section ".lprfd$M", comdat($foo_inline), align 8
+; COFF: @__profc_foo_inline = linkonce_odr dso_local global{{.*}}, section ".lprfc$M", comdat, align 8
+; COFF: @__profd_foo_inline = internal global{{.*}}, section ".lprfd$M", comdat($__profc_foo_inline), align 8
 define weak_odr void @foo_inline() comdat {
   call void @llvm.instrprof.increment(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @__profn_foo_inline, i32 0, i32 0), i64 0, i32 1, i32 0)
   ret void