r311898 - Revert r311857 "Emit static constexpr member as available_externally definition"

[Hans Wennborg via cfe-commits]

Author: hans
Date: Mon Aug 28 10:53:00 2017
New Revision: 311898

URL: http://llvm.org/viewvc/llvm-project?rev=311898&view=rev
Log:
Revert r311857 "Emit static constexpr member as available_externally definition"

It caused PR759744.

> Emit static constexpr member as available_externally definition
>
> By exposing the constant initializer, the optimizer can fold many
> of these constructs.
>
> Differential Revision: https://reviews.llvm.org/D34992

Removed:
    cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp
Modified:
    cfe/trunk/lib/CodeGen/CodeGenModule.cpp

Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=311898&r1=311897&r2=311898&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Mon Aug 28 10:53:00 2017
@@ -2437,28 +2437,6 @@ CodeGenModule::GetOrCreateLLVMGlobal(Str
         D->getType().isConstant(Context) &&
         isExternallyVisible(D->getLinkageAndVisibility().getLinkage()))
       GV->setSection(".cp.rodata");
-
-    // Check if we a have a const declaration with an initializer, we may be
-    // able to emit it as available_externally to expose it's value to the
-    // optimizer.
-    if (Context.getLangOpts().CPlusPlus && GV->hasExternalLinkage() &&
-        D->getType().isConstQualified() && !GV->hasInitializer() &&
-        !D->hasDefinition() && D->hasInit() && !D->hasAttr<DLLImportAttr>()) {
-      const auto *Record =
-          Context.getBaseElementType(D->getType())->getAsCXXRecordDecl();
-      bool HasMutableFields = Record && Record->hasMutableFields();
-      if (!HasMutableFields) {
-        const VarDecl *InitDecl;
-        const Expr *InitExpr = D->getAnyInitializer(InitDecl);
-        if (InitExpr) {
-          GV->setConstant(true);
-          GV->setLinkage(llvm::GlobalValue::AvailableExternallyLinkage);
-          ConstantEmitter emitter(*this);
-          GV->setInitializer(emitter.tryEmitForInitializer(*InitDecl));
-          emitter.finalize(GV);
-        }
-      }
-    }
   }
 
   auto ExpectedAS =

Removed: cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp?rev=311897&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp (removed)
@@ -1,55 +0,0 @@
-// RUN: %clang_cc1 -std=c++11 %s -emit-llvm -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK --check-prefix=CXX11
-// RUN: %clang_cc1 -std=c++1z %s -emit-llvm -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK --check-prefix=CXX17
-
-struct A {
-  static const int Foo = 123;
-};
-// CHECK: @_ZN1A3FooE = constant i32 123, align 4
-const int *p = &A::Foo; // emit available_externally
-const int A::Foo;       // convert to full definition
-
-struct Bar {
-  int b;
-};
-
-struct MutableBar {
-  mutable int b;
-};
-
-struct Foo {
-  // CXX11: @_ZN3Foo21ConstexprStaticMemberE = available_externally constant i32 42,
-  // CXX17: @_ZN3Foo21ConstexprStaticMemberE = linkonce_odr constant i32 42,
-  static constexpr int ConstexprStaticMember = 42;
-  // CHECK: @_ZN3Foo17ConstStaticMemberE = available_externally constant i32 43,
-  static const int ConstStaticMember = 43;
-
-  // CXX11: @_ZN3Foo23ConstStaticStructMemberE = available_externally constant %struct.Bar { i32 44 },
-  // CXX17: @_ZN3Foo23ConstStaticStructMemberE = linkonce_odr constant %struct.Bar { i32 44 },
-  static constexpr Bar ConstStaticStructMember = {44};
-
-  // CXX11: @_ZN3Foo34ConstexprStaticMutableStructMemberE = external global %struct.MutableBar,
-  // CXX17: @_ZN3Foo34ConstexprStaticMutableStructMemberE = linkonce_odr global %struct.MutableBar { i32 45 },
-  static constexpr MutableBar ConstexprStaticMutableStructMember = {45};
-};
-// CHECK: @_ZL15ConstStaticexpr = internal constant i32 46,
-static constexpr int ConstStaticexpr = 46;
-// CHECK: @_ZL9ConstExpr = internal constant i32 46, align 4
-static const int ConstExpr = 46;
-
-// CHECK: @_ZL21ConstexprStaticStruct = internal constant %struct.Bar { i32 47 },
-static constexpr Bar ConstexprStaticStruct = {47};
-
-// CHECK: @_ZL28ConstexprStaticMutableStruct = internal global %struct.MutableBar { i32 48 },
-static constexpr MutableBar ConstexprStaticMutableStruct = {48};
-
-void use(const int &);
-void foo() {
-  use(Foo::ConstexprStaticMember);
-  use(Foo::ConstStaticMember);
-  use(Foo::ConstStaticStructMember.b);
-  use(Foo::ConstexprStaticMutableStructMember.b);
-  use(ConstStaticexpr);
-  use(ConstExpr);
-  use(ConstexprStaticStruct.b);
-  use(ConstexprStaticMutableStruct.b);
-}