Add EAF_NOT_RETURNED_DIRECTLY

  Hi,
this patch adds EAF_NOT_RETURNED_DIRECTLY which works similarly as
EAF_NODIRECTESCAPE.  Values pointed to by a given argument may be returned but
not the argument itself.  This helps PTA quite noticeably because we mostly
care about tracking points to which given memory location can escape.

I think this is about last reasonable improvement we can get to EAF
flags.

cc1plus disambiguation counts change from:

Alias oracle query stats:
  refs_may_alias_p: 77976088 disambiguations, 98744590 queries
  ref_maybe_used_by_call_p: 572845 disambiguations, 79014622 queries
  call_may_clobber_ref_p: 340823 disambiguations, 344823 queries
  nonoverlapping_component_refs_p: 0 disambiguations, 26590 queries
  nonoverlapping_refs_since_match_p: 31626 disambiguations, 65379 must overlaps, 97963 queries
  aliasing_component_refs_p: 57414 disambiguations, 11434878 queries
  TBAA oracle: 27749649 disambiguations 91624184 queries
               14733408 are in alias set 0
               8847139 queries asked about the same object
               139 queries asked about the same alias set
               0 access volatile
               38412201 are dependent in the DAG
               1881648 are aritificially in conflict with void *

Modref stats:
  modref use: 23785 disambiguations, 702425 queries
  modref clobber: 2296391 disambiguations, 22690531 queries
  5260226 tbaa queries (0.231825 per modref query)
  731741 base compares (0.032249 per modref query)

PTA query stats:
  pt_solution_includes: 12580233 disambiguations, 35854408 queries
  pt_solutions_intersect: 1409041 disambiguations, 13496899 queries

To:

Alias oracle query stats:
  refs_may_alias_p: 78304485 disambiguations, 98830913 queries
  ref_maybe_used_by_call_p: 630360 disambiguations, 79308222 queries
  call_may_clobber_ref_p: 381549 disambiguations, 384627 queries
  nonoverlapping_component_refs_p: 0 disambiguations, 26299 queries
  nonoverlapping_refs_since_match_p: 29919 disambiguations, 64917 must overlaps, 95781 queries
  aliasing_component_refs_p: 57250 disambiguations, 11336880 queries
  TBAA oracle: 27835747 disambiguations 91534430 queries
               14884868 are in alias set 0
               8933627 queries asked about the same object
               123 queries asked about the same alias set
               0 access volatile
               37974723 are dependent in the DAG
               1905342 are aritificially in conflict with void *

Modref stats:
  modref use: 24929 disambiguations, 756294 queries
  modref clobber: 2334910 disambiguations, 23414495 queries
  5359212 tbaa queries (0.228884 per modref query)
  754642 base compares (0.032230 per modref query)

PTA query stats:
  pt_solution_includes: 13262256 disambiguations, 36306509 queries
  pt_solutions_intersect: 1574672 disambiguations, 13638933 queries

So about 5% more pt_solution_includes and 11% more pt_solutions_intersect
disambiguations.

Bootstrapped/regtested x86_64-linux, OK?

Honza

gcc/ChangeLog:

	* tree-core.h (EAF_NOT_RETURNED_DIRECTLY): New flag.
	(EAF_NOREAD): Renumber.
	* ipa-modref.c (dump_eaf_flags): Dump EAF_NOT_RETURNED_DIRECTLY.
	(remove_useless_eaf_flags): Handle EAF_NOT_RETURNED_DIRECTLY
	(deref_flags): Likewise.
	(modref_lattice::init): Likewise.
	(modref_lattice::merge): Likewise.
	(merge_call_lhs_flags): Likewise.
	(analyze_ssa_name_flags): Likewise.
	(modref_merge_call_site_flags): Likewise.
	* tree-ssa-structalias.c (handle_call_arg): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.dg/ipa/modref-3.c: New test.
	* gcc.dg/tree-ssa/modref-10.c: New test.
  

On Mon, 1 Nov 2021, Jan Hubicka wrote:

> Hi,
> this patch adds EAF_NOT_RETURNED_DIRECTLY which works similarly as
> EAF_NODIRECTESCAPE.  Values pointed to by a given argument may be returned but
> not the argument itself.  This helps PTA quite noticeably because we mostly
> care about tracking points to which given memory location can escape.
> 
> I think this is about last reasonable improvement we can get to EAF
> flags.
> 
> cc1plus disambiguation counts change from:
> 
> Alias oracle query stats:
>   refs_may_alias_p: 77976088 disambiguations, 98744590 queries
>   ref_maybe_used_by_call_p: 572845 disambiguations, 79014622 queries
>   call_may_clobber_ref_p: 340823 disambiguations, 344823 queries
>   nonoverlapping_component_refs_p: 0 disambiguations, 26590 queries
>   nonoverlapping_refs_since_match_p: 31626 disambiguations, 65379 must overlaps, 97963 queries
>   aliasing_component_refs_p: 57414 disambiguations, 11434878 queries
>   TBAA oracle: 27749649 disambiguations 91624184 queries
>                14733408 are in alias set 0
>                8847139 queries asked about the same object
>                139 queries asked about the same alias set
>                0 access volatile
>                38412201 are dependent in the DAG
>                1881648 are aritificially in conflict with void *
> 
> Modref stats:
>   modref use: 23785 disambiguations, 702425 queries
>   modref clobber: 2296391 disambiguations, 22690531 queries
>   5260226 tbaa queries (0.231825 per modref query)
>   731741 base compares (0.032249 per modref query)
> 
> PTA query stats:
>   pt_solution_includes: 12580233 disambiguations, 35854408 queries
>   pt_solutions_intersect: 1409041 disambiguations, 13496899 queries
> 
> To:
> 
> Alias oracle query stats:
>   refs_may_alias_p: 78304485 disambiguations, 98830913 queries
>   ref_maybe_used_by_call_p: 630360 disambiguations, 79308222 queries
>   call_may_clobber_ref_p: 381549 disambiguations, 384627 queries
>   nonoverlapping_component_refs_p: 0 disambiguations, 26299 queries
>   nonoverlapping_refs_since_match_p: 29919 disambiguations, 64917 must overlaps, 95781 queries
>   aliasing_component_refs_p: 57250 disambiguations, 11336880 queries
>   TBAA oracle: 27835747 disambiguations 91534430 queries
>                14884868 are in alias set 0
>                8933627 queries asked about the same object
>                123 queries asked about the same alias set
>                0 access volatile
>                37974723 are dependent in the DAG
>                1905342 are aritificially in conflict with void *
> 
> Modref stats:
>   modref use: 24929 disambiguations, 756294 queries
>   modref clobber: 2334910 disambiguations, 23414495 queries
>   5359212 tbaa queries (0.228884 per modref query)
>   754642 base compares (0.032230 per modref query)
> 
> PTA query stats:
>   pt_solution_includes: 13262256 disambiguations, 36306509 queries
>   pt_solutions_intersect: 1574672 disambiguations, 13638933 queries
> 
> So about 5% more pt_solution_includes and 11% more pt_solutions_intersect
> disambiguations.
> 
> Bootstrapped/regtested x86_64-linux, OK?

OK.

Thanks,
Richard.

> Honza
> 
> gcc/ChangeLog:
> 
> 	* tree-core.h (EAF_NOT_RETURNED_DIRECTLY): New flag.
> 	(EAF_NOREAD): Renumber.
> 	* ipa-modref.c (dump_eaf_flags): Dump EAF_NOT_RETURNED_DIRECTLY.
> 	(remove_useless_eaf_flags): Handle EAF_NOT_RETURNED_DIRECTLY
> 	(deref_flags): Likewise.
> 	(modref_lattice::init): Likewise.
> 	(modref_lattice::merge): Likewise.
> 	(merge_call_lhs_flags): Likewise.
> 	(analyze_ssa_name_flags): Likewise.
> 	(modref_merge_call_site_flags): Likewise.
> 	* tree-ssa-structalias.c (handle_call_arg): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.dg/ipa/modref-3.c: New test.
> 	* gcc.dg/tree-ssa/modref-10.c: New test.
> 
> diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
> index d866d9ed6b3..c0aae084dbd 100644
> --- a/gcc/ipa-modref.c
> +++ b/gcc/ipa-modref.c
> @@ -160,6 +160,8 @@ dump_eaf_flags (FILE *out, int flags, bool newline = true)
>      fprintf (out, " unused");
>    if (flags & EAF_NOT_RETURNED)
>      fprintf (out, " not_returned");
> +  if (flags & EAF_NOT_RETURNED_DIRECTLY)
> +    fprintf (out, " not_returned_directly");
>    if (flags & EAF_NOREAD)
>      fprintf (out, " noread");
>    if (newline)
> @@ -295,7 +297,7 @@ remove_useless_eaf_flags (int eaf_flags, int ecf_flags, bool returns_void)
>    else if (ecf_flags & ECF_PURE)
>      eaf_flags &= ~implicit_pure_eaf_flags;
>    else if ((ecf_flags & ECF_NORETURN) || returns_void)
> -    eaf_flags &= ~EAF_NOT_RETURNED;
> +    eaf_flags &= ~(EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY);
>    return eaf_flags;
>  }
>  
> @@ -1373,7 +1375,7 @@ memory_access_to (tree op, tree ssa_name)
>  static int
>  deref_flags (int flags, bool ignore_stores)
>  {
> -  int ret = EAF_NODIRECTESCAPE;
> +  int ret = EAF_NODIRECTESCAPE | EAF_NOT_RETURNED_DIRECTLY;
>    /* If argument is unused just account for
>       the read involved in dereference.  */
>    if (flags & EAF_UNUSED)
> @@ -1458,7 +1460,8 @@ modref_lattice::init ()
>  {
>    /* All flags we track.  */
>    int f = EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE | EAF_UNUSED
> -	  | EAF_NODIRECTESCAPE | EAF_NOT_RETURNED | EAF_NOREAD;
> +	  | EAF_NODIRECTESCAPE | EAF_NOT_RETURNED |
> +	  EAF_NOT_RETURNED_DIRECTLY | EAF_NOREAD;
>    flags = f;
>    /* Check that eaf_flags_t is wide enough to hold all flags.  */
>    gcc_checking_assert (f == flags);
> @@ -1540,6 +1543,8 @@ modref_lattice::merge (int f)
>       Fnspec machinery does set both so compensate for this.  */
>    if (f & EAF_NOESCAPE)
>      f |= EAF_NODIRECTESCAPE;
> +  if (f & EAF_NOT_RETURNED)
> +    f |= EAF_NOT_RETURNED_DIRECTLY;
>    if ((flags & f) != flags)
>      {
>        flags &= f;
> @@ -1647,7 +1652,9 @@ merge_call_lhs_flags (gcall *call, int arg, int index, bool deref,
>        && (flags & ERF_RETURN_ARG_MASK) != arg)
>      return;
>  
> -  if (gimple_call_arg_flags (call, arg) & (EAF_NOT_RETURNED | EAF_UNUSED))
> +  int eaf_flags = gimple_call_arg_flags (call, arg);
> +
> +  if (eaf_flags & (EAF_NOT_RETURNED | EAF_UNUSED))
>      return;
>  
>    /* If return value is SSA name determine its flags.  */
> @@ -1655,12 +1662,14 @@ merge_call_lhs_flags (gcall *call, int arg, int index, bool deref,
>      {
>        tree lhs = gimple_call_lhs (call);
>        analyze_ssa_name_flags (lhs, lattice, depth + 1, ipa);
> -      if (deref)
> +      if (deref || (eaf_flags & EAF_NOT_RETURNED_DIRECTLY))
>  	lattice[index].merge_deref (lattice[SSA_NAME_VERSION (lhs)], false);
>        else
>  	lattice[index].merge (lattice[SSA_NAME_VERSION (lhs)]);
>      }
>    /* In the case of memory store we can do nothing.  */
> +  else if (eaf_flags & EAF_NOT_RETURNED_DIRECTLY)
> +    lattice[index].merge (deref_flags (0, false));
>    else
>      lattice[index].merge (0);
>  }
> @@ -1731,11 +1740,13 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
>  	      && DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
>  	    ;
>  	  else if (gimple_return_retval (ret) == name)
> -	    lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED));
> +	    lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED
> +				    | EAF_NOT_RETURNED_DIRECTLY));
>  	  else if (memory_access_to (gimple_return_retval (ret), name))
>  	    {
>  	      lattice[index].merge_direct_load ();
> -	      lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED));
> +	      lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED
> +				      | EAF_NOT_RETURNED_DIRECTLY));
>  	    }
>  	}
>        /* Account for LHS store, arg loads and flags from callee function.  */
> @@ -1794,7 +1805,8 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
>  		    if (!(ecf_flags & (ECF_CONST | ECF_NOVOPS)))
>  		      {
>  			int call_flags = gimple_call_arg_flags (call, i)
> -					 | EAF_NOT_RETURNED;
> +					 | EAF_NOT_RETURNED
> +					 | EAF_NOT_RETURNED_DIRECTLY;
>  			if (ignore_stores)
>  			  call_flags |= ignore_stores_eaf_flags;
>  
> @@ -1817,7 +1829,8 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
>  		      {
>  			int call_flags = deref_flags
>  			   (gimple_call_arg_flags (call, i)
> -			    | EAF_NOT_RETURNED, ignore_stores);
> +			    | EAF_NOT_RETURNED
> +			    | EAF_NOT_RETURNED_DIRECTLY, ignore_stores);
>  			if (!record_ipa)
>  			  lattice[index].merge (call_flags);
>  			else
> @@ -3858,14 +3871,18 @@ modref_merge_call_site_flags (escape_summary *sum,
>  	  flags_lto |= ignore_stores_eaf_flags;
>  	}
>        /* Returning the value is already accounted to at local propagation.  */
> -      flags |= ee->min_flags | EAF_NOT_RETURNED;
> -      flags_lto |= ee->min_flags | EAF_NOT_RETURNED;
> +      flags |= ee->min_flags | EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY;
> +      flags_lto |= ee->min_flags | EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY;
>        /* Noescape implies that value also does not escape directly.
>  	 Fnspec machinery does set both so compensate for this.  */
>        if (flags & EAF_NOESCAPE)
>  	flags |= EAF_NODIRECTESCAPE;
>        if (flags_lto & EAF_NOESCAPE)
>  	flags_lto |= EAF_NODIRECTESCAPE;
> +      if (flags & EAF_NOT_RETURNED)
> +	flags |= EAF_NOT_RETURNED_DIRECTLY;
> +      if (flags_lto & EAF_NOT_RETURNED)
> +	flags_lto |= EAF_NOT_RETURNED_DIRECTLY;
>        if (!(flags & EAF_UNUSED)
>  	  && cur_summary && ee->parm_index < (int)cur_summary->arg_flags.length ())
>  	{
> diff --git a/gcc/testsuite/gcc.dg/ipa/modref-3.c b/gcc/testsuite/gcc.dg/ipa/modref-3.c
> new file mode 100644
> index 00000000000..c90683bc962
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/modref-3.c
> @@ -0,0 +1,20 @@
> +/* { dg-options "-O2 -fdump-ipa-modref"  } */
> +/* { dg-do link } */
> +int *ptr;
> +void linker_error ();
> +int
> +main ()
> +{
> +  int a;
> +  __attribute__((noinline)) int test2 ()
> +  {
> +    ptr = 0;
> +    return a;
> +  }
> +  a = 1;
> +  test2 ();
> +  if (a != 1)
> +    linker_error ();
> +  return 0;
> +}
> +/* { dg-final { scan-ipa-dump "Static chain flags: noclobber noescape nodirectescape" "modref" } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/modref-10.c b/gcc/testsuite/gcc.dg/tree-ssa/modref-10.c
> new file mode 100644
> index 00000000000..c608408809d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/modref-10.c
> @@ -0,0 +1,20 @@
> +/* { dg-do link } */
> +/* { dg-options "-O2 -fdump-tree-modref1"  } */
> +void linker_error ();
> +__attribute__((noinline))
> +int *
> +test (int **a)
> +{
> +  return *a;
> +}
> +int
> +main()
> +{
> +	int val;
> +	int *a=&val;
> +	int *b = test (&a);
> +	if (b == (int *)&a)
> +		linker_error ();
> +	return 0;
> +}
> +/* { dg-final { scan-tree-dump "parm 0 flags: noclobber noescape nodirectescape not_returned_directly" "modref1"} } */
> diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> index d3d2a8d812f..8a55db2b3f5 100644
> --- a/gcc/tree-core.h
> +++ b/gcc/tree-core.h
> @@ -117,8 +117,12 @@ struct die_struct;
>  /* Nonzero if the argument does not escape to return value.  */
>  #define EAF_NOT_RETURNED	(1 << 5)
>  
> +/* Nonzero if the argument argument itself does not escape
> +   to return value but memory referenced by it may escape.  */
> +#define EAF_NOT_RETURNED_DIRECTLY (1 << 6)
> +
>  /* Nonzero if the argument is not read.  */
> -#define EAF_NOREAD		(1 << 6)
> +#define EAF_NOREAD		(1 << 7)
>  
>  /* Call return flags.  */
>  /* Mask for the argument number that is returned.  Lower two bits of
> diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
> index 99072df0768..5f24c0171f0 100644
> --- a/gcc/tree-ssa-structalias.c
> +++ b/gcc/tree-ssa-structalias.c
> @@ -4082,8 +4082,16 @@ handle_call_arg (gcall *stmt, tree arg, vec<ce_s> *results, int flags,
>      {
>        struct constraint_expr cexpr;
>        cexpr.var = tem->id;
> -      cexpr.type = SCALAR;
> -      cexpr.offset = 0;
> +      if (flags & EAF_NOT_RETURNED_DIRECTLY)
> +	{
> +	  cexpr.type = DEREF;
> +	  cexpr.offset = UNKNOWN_OFFSET;
> +	}
> +      else
> +	{
> +	  cexpr.type = SCALAR;
> +	  cexpr.offset = 0;
> +	}
>        results->safe_push (cexpr);
>      }
>  
>