https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58483
--- Comment #11 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #10)
> Wit GCC 9 and trunk we are left with
>
> <bb 2> [local count: 118111600]:
> MEM[(int *)&D.30957] = 85899345930;
> D.30957[2] = 30;
> _33 = operator new (12);
> __builtin_memcpy (_33, &D.30957, 12);
> _41 = MEM[(const int &)_33];
> __init_42 = _41 + 100;
> _50 = MEM[(const int &)_33 + 4];
> __init_19 = __init_42 + _50;
> _14 = MEM[(const int &)_33 + 8];
> __init_16 = _14 + __init_19;
> operator delete (_33);
> D.30957 ={v} {CLOBBER};
> return __init_16;
>
> here I think operator new clobbers D.30957 which escapes at the memcpy call.
I thought we had code saying that nothing can escape through memcpy?
> This prevents a late FRE from doing its job (not sure if a late one is
> really needed).
With
#include <new>
inline void* operator new(std::size_t n){return __builtin_malloc(n);}
inline void operator delete(void*p)noexcept{__builtin_free(p);}
inline void operator delete(void*p,std::size_t)noexcept{__builtin_free(p);}
I get
_33 = __builtin_malloc (12);
MEM[(char * {ref-all})_33] = 85899345930;
MEM[(char * {ref-all})_33 + 8B] = 30;
_12 = MEM[(const int &)_33];
__init_49 = _12 + 100;
_38 = MEM[(const int &)_33 + 4];
__init_36 = _38 + __init_49;
_14 = MEM[(const int &)_33 + 8];
__init_16 = _14 + __init_36;
__builtin_free (_33);
return __init_16;
where FRE should work.
