[Bug d/96156] New: d: No RVO when returning struct literals initialized with constructor.

[Bug d/96156] New: d: No RVO when returning struct literals initialized with constructor.

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96156

            Bug ID: 96156
           Summary: d: No RVO when returning struct literals initialized
                    with constructor.
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: d
          Assignee: ibuclaw at gdcproject dot org
          Reporter: ibuclaw at gdcproject dot org
  Target Milestone: ---

The address of 's' should become the 'this' pointer of the __ctor() call.

struct S66 {
    int x;
    __gshared void* ptr;
    @disable this(this);
    this(int x) { ptr = &this; this.x = x; }
}
auto f66() { return g66(); }
auto g66() { return h66(); }
auto h66() { return S66(100); }
void main()
{
    auto s = f66();
    assert(&s == S66.ptr);
}

[Bug d/96156] d: No RVO when returning struct literals initialized with constructor.

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96156

--- Comment #1 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
The fix for this is blocked by pr96347.

[Bug d/96156] d: No RVO when returning struct literals initialized with constructor.

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96156

Iain Buclaw <ibuclaw at gdcproject dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|96347                       |

--- Comment #2 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
Generated code has been sufficiently altered that it is no longer blocked, but
the underlying depends-on bug still exists under the right conditions.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96347
[Bug 96347] note: non-delegitimized UNSPEC UNSPEC_TP (19) found in variable
location

[Bug d/96156] d: No RVO when returning struct literals initialized with constructor.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96156

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Iain Buclaw <ibuclaw@gcc.gnu.org>:

https://gcc.gnu.org/g:87e36d9baf41a8642ca8687e846764e0828a088b

commit r11-2869-g87e36d9baf41a8642ca8687e846764e0828a088b
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Fri Jul 24 18:06:51 2020 +0200

    d: Fix no RVO when returning struct literals initialized with constructor.

    Backports a change from upstream dmd that moves front-end NRVO checking
    from ReturnStatement semantic to the end of FuncDeclaration semantic.

    In the codegen, retStyle has been partially implemented so that only
    structs and static arrays return RETstack.  This isn't accurate, but
    don't need to be for the purposes of semantic analysis.

    If a function either has TREE_ADDRESSABLE or must return in memory, then
    DECL_RESULT is set as the shidden field for the function.  This is used
    in the codegen pass for ReturnStatement where it is now detected whether
    a function is returning a struct literal or a constructor function, then
    the DECL_RESULT is used to directly construct the return value, instead
    of doing so via temporaries.

    Reviewed-on: https://github.com/dlang/dmd/pull/11622

    gcc/d/ChangeLog:

            PR d/96156
            * d-frontend.cc (retStyle): Only return RETstack for struct and
static
            array types.
            * decl.cc (DeclVisitor::visit (FuncDeclaration *)): Use NRVO return
            for all TREE_ADDRESSABLE types.  Set shidden to the RESULT_DECL.
            * expr.cc (ExprVisitor::visit (CallExp *)): Force TARGET_EXPR if
the
            'this' pointer reference is a CONSTRUCTOR.
            (ExprVisitor::visit (StructLiteralExp *)): Generate assignment to
the
            symbol to initialize with literal.
            * toir.cc (IRVisitor::visit (ReturnStatement *)): Detect returning
            struct literals and write directly into the RESULT_DECL.
            * dmd/MERGE: Merge upstream dmd fe5f388d8.

    gcc/testsuite/ChangeLog:

            PR d/96156
            * gdc.dg/pr96156.d: New test.

[Bug d/96156] d: No RVO when returning struct literals initialized with constructor.

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96156

Iain Buclaw <ibuclaw at gdcproject dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #4 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
Done.