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@194046 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index 25f3e6f..ab45e32 100644
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -112,28 +112,13 @@
// 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);
@@ -152,6 +137,26 @@
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) {
+ if (!Entry)
+ return false;
+
+ Entry->replaceAllUsesWith(Aliasee);
+ Entry->eraseFromParent();
+ return false;
+ }
+ }
+
// Create the alias with no name.
llvm::GlobalAlias *Alias =
new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule());
diff --git a/test/CodeGenCXX/ctor-dtor-alias.cpp b/test/CodeGenCXX/ctor-dtor-alias.cpp
index e658522..ff9bd7c 100644
--- a/test/CodeGenCXX/ctor-dtor-alias.cpp
+++ b/test/CodeGenCXX/ctor-dtor-alias.cpp
@@ -13,12 +13,11 @@
}
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 @@
// 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 0030aae..fa7df1b 100644
--- a/test/CodeGenCXX/destructors.cpp
+++ b/test/CodeGenCXX/destructors.cpp
@@ -9,7 +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
struct A {
int a;
@@ -45,6 +44,9 @@
// 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;
}