[cfe-commits] r103904 - in /cfe/trunk: lib/AST/ExprConstant.cpp test/CodeGenCXX/references.cpp
Chandler Carruth
chandlerc at gmail.com
Sun May 16 13:49:51 PDT 2010
On Sun, May 16, 2010 at 1:44 PM, Douglas Gregor <dgregor at apple.com> wrote:
> I am beginning to doubt our decision to inherit ParmVarDecl from VarDecl.
>
I can't tell whether that is the problem, or whether the decision to
represent default arguments as initializers is the problem. Fundamentally,
parameters *are* variables within the function, so it does seem a
reasonable way to represent them.
A slight counter proposal: we re-use the storage of initializers for default
arguments, but the accessor methods for initializers should filter them out,
and ParmVarDecl should provide a dedicated API. Would that resolve this?
Does it introduce other problems?
>
> Sent from my iPhone
>
> On May 16, 2010, at 2:32 AM, Chandler Carruth <chandlerc at gmail.com> wrote:
>
> > Author: chandlerc
> > Date: Sun May 16 04:32:51 2010
> > New Revision: 103904
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=103904&view=rev
> > Log:
> > When constant folding reference variables with an initializer to the
> > initializer, don't fold paramters. Their initializers are just default
> > arguments which can be overridden. This fixes some spectacular
> regressions due
> > to more things making it into the constant folding.
> >
> > Modified:
> > cfe/trunk/lib/AST/ExprConstant.cpp
> > cfe/trunk/test/CodeGenCXX/references.cpp
> >
> > Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=103904&r1=103903&r2=103904&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> > +++ cfe/trunk/lib/AST/ExprConstant.cpp Sun May 16 04:32:51 2010
> > @@ -355,6 +355,10 @@
> > } else if (VarDecl* VD = dyn_cast<VarDecl>(E->getDecl())) {
> > if (!VD->getType()->isReferenceType())
> > return Success(E);
> > + // Reference parameters can refer to anything even if they have an
> > + // "initializer" in the form of a default argument.
> > + if (isa<ParmVarDecl>(VD))
> > + return false;
> > // FIXME: Check whether VD might be overridden!
> > if (const Expr *Init = VD->getAnyInitializer())
> > return Visit(const_cast<Expr *>(Init));
> >
> > Modified: cfe/trunk/test/CodeGenCXX/references.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/references.cpp?rev=103904&r1=103903&r2=103904&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/test/CodeGenCXX/references.cpp (original)
> > +++ cfe/trunk/test/CodeGenCXX/references.cpp Sun May 16 04:32:51 2010
> > @@ -155,3 +155,16 @@
> > // CHECK: load
> > // CHECK: ret
> > const int &f2() { return 0; }
> > +
> > +// Don't constant fold const reference parameters with default arguments
> to
> > +// their default arguments.
> > +namespace N1 {
> > + const int foo = 1;
> > + // CHECK: @_ZN2N14test
> > + int test(const int& arg = foo) {
> > + // Ensure this array is on the stack where we can set values instead
> of
> > + // being a global constant.
> > + // CHECK: %args_array = alloca
> > + const int* const args_array[] = { &arg };
> > + }
> > +}
> >
> >
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