[Bug d/101273] New: d: missed RVO optimization with non-pod structs

[Bug d/101273] New: d: missed RVO optimization with non-pod structs

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101273

            Bug ID: 101273
           Summary: d: missed RVO optimization with non-pod structs
           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: ---

It looks like fixing PR d/100882 introduced a small regression:
---
struct S
{
    int x;
    S *impl;
    this(int x)
    {
        this.x = x;
        this.impl = &this;
    }
    ~this() { }
}

S makeS()
{
    return S(42);
}

S nrvo()
{
    S ret = S(2);
    return ret; 
}

S rvo()
{
    return makeS(); 
}

void main()
{
    auto a1 = nrvo();
    assert(&a1 is a1.impl);
    auto b1 = rvo();
    assert(&b1 is b1.impl);
    return;
}

[Bug d/101273] d: missed RVO optimization with non-pod structs

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101273

--- Comment #1 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
(In reply to Iain Buclaw from comment #0)
> It looks like fixing PR d/100882 introduced a small regression:
On further inspection, this is not the case.  The front-end semantic pass
returns us code that uses an intermediate temporary. i.e:

  return __ctor((S tmp = S(), &tmp), 42);

The code generator in D just doesn't detect this pattern and replace `tmp' with
the DECL_RESULT variable to give us a more desired representation:

  S tmp [value-expr: <retval>];
  __ctor(<retval> = S(), &<retval>, 42);
  return <retval>;

[Bug d/101273] d: missed RVO optimization with non-pod structs

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101273

--- Comment #2 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:152f4d0e4d3b524ce30d05f20e23a44b0dd29765

commit r12-1995-g152f4d0e4d3b524ce30d05f20e23a44b0dd29765
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Sat Jul 3 02:42:14 2021 +0200

    d: Missed RVO optimization with non-POD structs

    The D front-end semantic pass sometimes declares a temporary inside a
    return expression.  This is now detected with the RESULT_DECL replacing
    the temporary, allowing for RVO to be done.

            PR d/101273

    gcc/d/ChangeLog:

            * toir.cc (IRVisitor::visit (ReturnStatement *)): Detect returns
that
            use a temporary, and replace with return value.

    gcc/testsuite/ChangeLog:

            * gdc.dg/torture/pr101273.d: New test.

[Bug d/101273] d: missed RVO optimization with non-pod structs

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101273

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Iain Buclaw
<ibuclaw@gcc.gnu.org>:

https://gcc.gnu.org/g:46d1cb4c218ff1fb73b391a28218ee1f362e8ca1

commit r11-8688-g46d1cb4c218ff1fb73b391a28218ee1f362e8ca1
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Sat Jul 3 02:42:14 2021 +0200

    d: Missed RVO optimization with non-POD structs

    The D front-end semantic pass sometimes declares a temporary inside a
    return expression.  This is now detected with the RESULT_DECL replacing
    the temporary, allowing for RVO to be done.

            PR d/101273

    gcc/d/ChangeLog:

            * toir.cc (IRVisitor::visit (ReturnStatement *)): Detect returns
that
            use a temporary, and replace with return value.

    gcc/testsuite/ChangeLog:

            * gdc.dg/torture/pr101273.d: New test.

    (cherry picked from commit 152f4d0e4d3b524ce30d05f20e23a44b0dd29765)

[Bug d/101273] d: missed RVO optimization with non-pod structs

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101273

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> ---
Fixed.