From 61a0a7519ee0d26334d30a001501b8c443d36975 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Tue, 5 Nov 2013 21:37:29 +0000
Subject: [PATCH] Produce direct calls instead of alias to linkonce_odr
functions.
This is a small optimization on linux, but should help more on windows
where msvc only outputs one destructor if there would be two identical ones.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194095 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/CodeGen/CGCXX.cpp | 39 ++++++++++++++++-------------
lib/CodeGen/CodeGenModule.cpp | 15 +++++++++++
lib/CodeGen/CodeGenModule.h | 6 +++++
test/CodeGenCXX/ctor-dtor-alias.cpp | 9 +++----
test/CodeGenCXX/destructors.cpp | 10 +++++---
5 files changed, 51 insertions(+), 28 deletions(-)
diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index 31134be810..15686f7ff6 100644
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -112,33 +112,20 @@ bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
// support aliases with that linkage, fail.
llvm::GlobalValue::LinkageTypes Linkage = getFunctionLinkage(AliasDecl);
- llvm::GlobalValue::LinkageTypes TargetLinkage
- = getFunctionLinkage(TargetDecl);
-
- // Don't create an alias to a linker weak symbol unless we know we can do
- // that in every TU. This avoids producing different COMDATs in different
- // TUs.
- if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) {
- if (!InEveryTU)
- return true;
-
- // In addition to making sure we produce it in every TU, we have to make
- // sure llvm keeps it.
- // FIXME: Instead of outputting an alias we could just replace every use of
- // AliasDecl with TargetDecl.
- assert(Linkage == TargetLinkage);
- Linkage = llvm::GlobalValue::WeakODRLinkage;
- }
-
// We can't use an alias if the linkage is not valid for one.
if (!llvm::GlobalAlias::isValidLinkage(Linkage))
return true;
+ llvm::GlobalValue::LinkageTypes TargetLinkage =
+ getFunctionLinkage(TargetDecl);
+
// Check if we have it already.
StringRef MangledName = getMangledName(AliasDecl);
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
if (Entry && !Entry->isDeclaration())
return false;
+ if (Replacements.count(MangledName))
+ return false;
// Derive the type for the alias.
llvm::PointerType *AliasType
@@ -152,6 +139,22 @@ bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
if (Ref->getType() != AliasType)
Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType);
+ // Don't create an alias to a linker weak symbol unless we know we can do
+ // that in every TU. This avoids producing different COMDATs in different
+ // TUs.
+ if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) {
+ if (!InEveryTU)
+ return true;
+
+ assert(Linkage == TargetLinkage);
+ // Instead of creating as alias to a linkonce_odr, replace all of the uses
+ // of the aliassee.
+ if (TargetLinkage == llvm::GlobalValue::LinkOnceODRLinkage) {
+ Replacements[MangledName] = Aliasee;
+ return false;
+ }
+ }
+
// Create the alias with no name.
llvm::GlobalAlias *Alias =
new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule());
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index c34f833269..d7f33c9f1e 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -172,6 +172,20 @@ void CodeGenModule::createCUDARuntime() {
CUDARuntime = CreateNVCUDARuntime(*this);
}
+void CodeGenModule::applyReplacements() {
+ for (ReplacementsTy::iterator I = Replacements.begin(),
+ E = Replacements.end();
+ I != E; ++I) {
+ StringRef MangledName = I->first();
+ llvm::Constant *Replacement = I->second;
+ llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
+ if (!Entry)
+ continue;
+ Entry->replaceAllUsesWith(Replacement);
+ Entry->eraseFromParent();
+ }
+}
+
void CodeGenModule::checkAliases() {
bool Error = false;
for (std::vector<GlobalDecl>::iterator I = Aliases.begin(),
@@ -207,6 +221,7 @@ void CodeGenModule::checkAliases() {
void CodeGenModule::Release() {
EmitDeferred();
+ applyReplacements();
checkAliases();
EmitCXXGlobalInitFunc();
EmitCXXGlobalDtorFunc();
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index 45a9e20a51..02b9ce6471 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -279,6 +279,9 @@ class CodeGenModule : public CodeGenTypeCache {
/// is defined once we get to the end of the of the translation unit.
std::vector<GlobalDecl> Aliases;
+ typedef llvm::StringMap<llvm::TrackingVH<llvm::Constant> > ReplacementsTy;
+ ReplacementsTy Replacements;
+
/// DeferredVTables - A queue of (optional) vtables to consider emitting.
std::vector<const CXXRecordDecl*> DeferredVTables;
@@ -1082,6 +1085,9 @@ private:
/// was deferred.
void EmitDeferred();
+ /// Call replaceAllUsesWith on all pairs in Replacements.
+ void applyReplacements();
+
void checkAliases();
/// EmitDeferredVTables - Emit any vtables which we deferred and
diff --git a/test/CodeGenCXX/ctor-dtor-alias.cpp b/test/CodeGenCXX/ctor-dtor-alias.cpp
index e658522d79..ff9bd7c5c5 100644
--- a/test/CodeGenCXX/ctor-dtor-alias.cpp
+++ b/test/CodeGenCXX/ctor-dtor-alias.cpp
@@ -13,12 +13,11 @@ template struct foobar<void>;
}
namespace test2 {
-// test that we produce an alias when the destrucor is linkonce_odr. Note that
-// the alias itself is weak_odr to make sure we don't get a translation unit
-// with just _ZN5test26foobarIvEC2Ev in it.
+// test that when the destrucor is linkonce_odr we just replace every use of
+// C1 with C2.
-// CHECK-DAG: @_ZN5test26foobarIvEC1Ev = alias weak_odr void (%"struct.test2::foobar"*)* @_ZN5test26foobarIvEC2Ev
// CHECK-DAG: define linkonce_odr void @_ZN5test26foobarIvEC2Ev(
+// CHECK-DAG: call void @_ZN5test26foobarIvEC2Ev
void g();
template <typename T> struct foobar {
foobar() { g(); }
@@ -48,9 +47,7 @@ namespace test4 {
// Test that we don't produce aliases from B to A. We cannot because we cannot
// guarantee that they will be present in every TU.
- // CHECK-DAG: @_ZN5test41BD1Ev = alias weak_odr void (%"struct.test4::B"*)* @_ZN5test41BD2Ev
// CHECK-DAG: define linkonce_odr void @_ZN5test41BD2Ev(
- // CHECK-DAG: @_ZN5test41AD1Ev = alias weak_odr void (%"struct.test4::A"*)* @_ZN5test41AD2Ev
// CHECK-DAG: define linkonce_odr void @_ZN5test41AD2Ev(
struct A {
virtual ~A() {}
diff --git a/test/CodeGenCXX/destructors.cpp b/test/CodeGenCXX/destructors.cpp
index 472a229a9b..887b73fcc5 100644
--- a/test/CodeGenCXX/destructors.cpp
+++ b/test/CodeGenCXX/destructors.cpp
@@ -9,8 +9,6 @@
// CHECK-DAG: @_ZN5test312_GLOBAL__N_11DD1Ev = alias internal {{.*}} @_ZN5test312_GLOBAL__N_11DD2Ev
// CHECK-DAG: @_ZN5test312_GLOBAL__N_11DD2Ev = alias internal bitcast {{.*}} @_ZN5test312_GLOBAL__N_11CD2Ev
// CHECK-DAG: @_ZN5test312_GLOBAL__N_11CD1Ev = alias internal {{.*}} @_ZN5test312_GLOBAL__N_11CD2Ev
-// CHECK-DAG: @_ZN6PR752617allocator_derivedD1Ev = alias weak_odr void (%"struct.PR7526::allocator_derived"*)* @_ZN6PR752617allocator_derivedD2Ev
-// CHECK-DAG: @_ZN6test106OptionD1Ev = alias weak_odr void (%"struct.test10::Option"*)* @_ZN6test106OptionD2Ev
struct A {
int a;
@@ -46,6 +44,9 @@ namespace PR7526 {
// CHECK: call void @__cxa_call_unexpected
allocator::~allocator() throw() { foo(); }
+ // CHECK-LABEL: define void @_ZN6PR75263fooEv()
+ // CHECK: call void @_ZN6PR752617allocator_derivedD2Ev
+
void foo() {
allocator_derived ad;
}
@@ -367,14 +368,15 @@ namespace test9 {
namespace test10 {
// We used to crash trying to replace _ZN6test106OptionD1Ev with
- // _ZN6test106OptionD2Ev twice. For now check that we don't try and produce
- // an alias instead (check at the top of the file).
+ // _ZN6test106OptionD2Ev twice.
struct Option {
virtual ~Option() {}
};
template <class DataType> class opt : public Option {};
template class opt<int>;
+ // CHECK-LABEL: define zeroext i1 @_ZN6test1016handleOccurrenceEv(
bool handleOccurrence() {
+ // CHECK: call void @_ZN6test106OptionD2Ev(
Option x;
return true;
}
--
2.40.0