Re: [PATCH] tree-optimization/97151 - improve PTA for C++ operator delete

[Jason Merrill <jason@redhat.com>]

On 9/23/20 4:14 AM, Richard Biener wrote:
> C++ operator delete, when DECL_IS_REPLACEABLE_OPERATOR_DELETE_P,
> does not cause the deleted object to be escaped.  It also has no
> other interesting side-effects for PTA so skip it like we do
> for BUILT_IN_FREE.

Hmm, this is true of the default implementation, but since the function 
is replaceable, we don't know what a user definition might do with the 
pointer.

> Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
> 
> Richard.
> 
> 2020-09-23  Richard Biener  <rguenther@suse.de>
> 
> 	PR tree-optimization/97151
> 	* tree-ssa-structalias.c (find_func_aliases_for_call):
> 	DECL_IS_REPLACEABLE_OPERATOR_DELETE_P has no effect on
> 	arguments.
> 
> 	* g++.dg/cpp1y/new1.C: Adjust for two more handled transforms.
> ---
>   gcc/testsuite/g++.dg/cpp1y/new1.C | 4 ++--
>   gcc/tree-ssa-structalias.c        | 2 ++
>   2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/gcc/testsuite/g++.dg/cpp1y/new1.C b/gcc/testsuite/g++.dg/cpp1y/new1.C
> index aa5f647d535..fec0088cb40 100644
> --- a/gcc/testsuite/g++.dg/cpp1y/new1.C
> +++ b/gcc/testsuite/g++.dg/cpp1y/new1.C
> @@ -69,5 +69,5 @@ test_unused() {
>     delete p;
>   }
>   
> -/* { dg-final { scan-tree-dump-times "Deleting : operator delete" 5 "cddce1"} } */
> -/* { dg-final { scan-tree-dump-times "Deleting : _\\d+ = operator new" 7 "cddce1"} } */
> +/* { dg-final { scan-tree-dump-times "Deleting : operator delete" 6 "cddce1"} } */
> +/* { dg-final { scan-tree-dump-times "Deleting : _\\d+ = operator new" 8 "cddce1"} } */
> diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
> index 44fe52e0f65..f676bf91e95 100644
> --- a/gcc/tree-ssa-structalias.c
> +++ b/gcc/tree-ssa-structalias.c
> @@ -4857,6 +4857,8 @@ find_func_aliases_for_call (struct function *fn, gcall *t)
>   	 point for reachable memory of their arguments.  */
>         else if (flags & (ECF_PURE|ECF_LOOPING_CONST_OR_PURE))
>   	handle_pure_call (t, &rhsc);
> +      else if (fndecl && DECL_IS_REPLACEABLE_OPERATOR_DELETE_P (fndecl))
> +	;
>         else
>   	handle_rhs_call (t, &rhsc);
>         if (gimple_call_lhs (t))
>