r311857 - Emit static constexpr member as available_externally definition

[Mehdi AMINI via cfe-commits]

Sorry for the inconvenience!

I will follow-up in the PR.

-- 
Mehdi


2017-08-28 12:42 GMT-07:00 Hans Wennborg <hans at chromium.org>:

> I reverted this in r311898 as it caused Chromium builds to fail with
> an assertion; see PR34348.
>
> On Sun, Aug 27, 2017 at 1:24 PM, Mehdi Amini via cfe-commits
> <cfe-commits at lists.llvm.org> wrote:
> > Author: mehdi_amini
> > Date: Sun Aug 27 13:24:09 2017
> > New Revision: 311857
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=311857&view=rev
> > Log:
> > 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
> >
> > Added:
> >     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=311857&r1=311856&r2=311857&view=diff
> > ============================================================
> ==================
> > --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
> > +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Sun Aug 27 13:24:09 2017
> > @@ -2437,6 +2437,28 @@ 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 =
> >
> > Added: cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp
> > URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> CodeGenCXX/cxx11-extern-constexpr.cpp?rev=311857&view=auto
> > ============================================================
> ==================
> > --- cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp (added)
> > +++ cfe/trunk/test/CodeGenCXX/cxx11-extern-constexpr.cpp Sun Aug 27
> 13:24:09 2017
> > @@ -0,0 +1,55 @@
> > +// 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);
> > +}
> >
> >
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>
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