Set function entry count.

[dnovillo]

Summary

I don't particularly like this approach.

The change in linkage for link once symbols is needed for ELF targets.
Although the symbol is only associated once, the discarded symbols
still occupy memory. This causes duplicate count problem at runtime
because the raw profile contains multiple copies of the same data
record (see https://llvm.org/bugs/show_bug.cgi?id=23499 for details).

[echristo]

As we commented in IRC this isn't going to be the correct way to do it. I've updated the PR accordingly and we should go ahead with that solution. Probably want to close this revision.

Thanks!

-eric

lib/CodeGen/CodeGenPGO.cpp

void CodeGenPGO::createFuncNameVar(llvm::GlobalValue::LinkageTypes Linkage) {
   // We generally want to match the function's linkage, but available_externally
   // and extern_weak both have the wrong semantics, and anything that doesn't
   // need to link across compilation units doesn't need to be visible at all.
   if (Linkage == llvm::GlobalValue::ExternalWeakLinkage)
     Linkage = llvm::GlobalValue::LinkOnceAnyLinkage;
   else if (Linkage == llvm::GlobalValue::AvailableExternallyLinkage)
     Linkage = llvm::GlobalValue::LinkOnceODRLinkage;
   else if (Linkage == llvm::GlobalValue::InternalLinkage ||
-           Linkage == llvm::GlobalValue::ExternalLinkage)
+           Linkage == llvm::GlobalValue::ExternalLinkage ||
+           Linkage == llvm::GlobalValue::LinkOnceODRLinkage)
     Linkage = llvm::GlobalValue::PrivateLinkage;
 
   auto *Value =
       llvm::ConstantDataArray::getString(CGM.getLLVMContext(), FuncName, false);
   FuncNameVar =
       new llvm::GlobalVariable(CGM.getModule(), Value->getType(), true, Linkage,
                                Value, "__llvm_profile_name_" + FuncName);
 
CodeGenPGO::applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
   if (FunctionCount >= (uint64_t)(0.3 * (double)MaxFunctionCount))
     // Turn on InlineHint attribute for hot functions.
     // FIXME: 30% is from preliminary tuning on SPEC, it may not be optimal.
     Fn->addFnAttr(llvm::Attribute::InlineHint);
   else if (FunctionCount <= (uint64_t)(0.01 * (double)MaxFunctionCount))
     // Turn on Cold attribute for cold functions.
     // FIXME: 1% is from preliminary tuning on SPEC, it may not be optimal.
     Fn->addFnAttr(llvm::Attribute::Cold);
+
+  Fn->setEntryCount(FunctionCount);
 }
 
 void CodeGenPGO::emitCounterIncrement(CGBuilderTy &Builder, const Stmt *S) {
   if (!CGM.getCodeGenOpts().ProfileInstrGenerate || !RegionCounterMap)
     return;
   if (!Builder.GetInsertPoint())
     return;
 

test/Profile/cxx-linkage.cpp

 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.9.0 -emit-llvm -main-file-name cxx-linkage.cpp %s -o - -fprofile-instr-generate | FileCheck %s
 
 // CHECK: @__llvm_profile_name__Z3foov = private constant [7 x i8] c"_Z3foov"
 // CHECK: @__llvm_profile_name__Z8foo_weakv = weak hidden constant [12 x i8] c"_Z8foo_weakv"
 // CHECK: @__llvm_profile_name_main = private constant [4 x i8] c"main"
-// CHECK: @__llvm_profile_name__Z10foo_inlinev = linkonce_odr hidden constant [15 x i8] c"_Z10foo_inlinev"
+// CHECK: @__llvm_profile_name__Z10foo_inlinev = private constant [15 x i8] c"_Z10foo_inlinev"
 
 void foo(void) { }
 
 void foo_weak(void) __attribute__((weak));
 void foo_weak(void) { if (0){} if (0){} if (0){} if (0){} }
 
 inline void foo_inline(void);
 int main(void) {
   foo();
   foo_inline();
   foo_weak();
   return 0;
 }
 
 inline void foo_inline(void) { if (0){} if (0){} if (0){} if (0){} if (0){} if (0){}}

test/Profile/cxx-templates.cpp

 // Tests for instrumentation of templated code. Each instantiation of a template
 // should be instrumented separately.
 
 // RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-templates.cpp -std=c++11 -o - -emit-llvm -fprofile-instr-generate > %tgen
 // RUN: FileCheck --input-file=%tgen -check-prefix=T0GEN -check-prefix=ALL %s
 // RUN: FileCheck --input-file=%tgen -check-prefix=T100GEN -check-prefix=ALL %s
 
 // RUN: llvm-profdata merge %S/Inputs/cxx-templates.proftext -o %t.profdata
 // RUN: %clang_cc1 -x c++ %s -triple %itanium_abi_triple -main-file-name cxx-templates.cpp -std=c++11 -o - -emit-llvm -fprofile-instr-use=%t.profdata > %tuse
 // 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:__llvm_profile_counters__Z4loopILj0EEvv]] = linkonce_odr hidden global [2 x i64] zeroinitializer
-// T100GEN: @[[T100C:__llvm_profile_counters__Z4loopILj100EEvv]] = linkonce_odr hidden global [2 x i64] zeroinitializer
+// T0GEN: @[[T0C:__llvm_profile_counters__Z4loopILj0EEvv]] = private global [2 x i64] zeroinitializer
+// T100GEN: @[[T100C:__llvm_profile_counters__Z4loopILj100EEvv]] = private global [2 x i64] zeroinitializer
 
 // T0GEN-LABEL: define linkonce_odr void @_Z4loopILj0EEvv()
 // T0USE-LABEL: define linkonce_odr void @_Z4loopILj0EEvv()
 // T100GEN-LABEL: define linkonce_odr void @_Z4loopILj100EEvv()
 // T100USE-LABEL: define linkonce_odr void @_Z4loopILj100EEvv()
 template <unsigned N> void loop() {
   // ALL-NOT: ret
   // T0GEN: store {{.*}} @[[T0C]], i64 0, i64 0