[Bug target/104529] [12 Regression] inefficient codegen around new/delete

["tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104529

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[missed optimization]       |[12 Regression] inefficient
                   |inefficient codegen around  |codegen around new/delete
                   |new/delete                  |
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|DUPLICATE                   |---

--- Comment #3 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
I'm re-opening because I don't think it has anything to do with #94294

This is a GCC 12 regression.

In GCC 11 we generated in the mid-end

  <bb 2> [local count: 536870913]:
  _32 = operator new (6);
  MEM <unsigned int> [(char * {ref-all})_32] = 255;
  MEM <unsigned short> [(char * {ref-all})_32 + 4B] = 0;
  operator delete (_32, 6);
  return 56;

and in GCC 12 we now generate

  <bb 2> [local count: 536870913]:
  MEM <vector(4) unsigned char> [(unsigned char *)&D.24688] = { 255, 0, 0, 0 };
  MEM <vector(2) unsigned char> [(unsigned char *)&D.24688 + 4B] = { 0, 0 };
  _34 = operator new (6);
  MEM <unsigned char[6]> [(char * {ref-all})_34] = MEM <unsigned char[6]>
[(char * {ref-all})&D.24688];
  D.24688 ={v} {CLOBBER(eol)};
  operator delete (_34, 6);
  return 56;

See https://godbolt.org/z/KKfhxTxnd

Forcing it to keep the stores before the call to new.