Fix PR79547

On Thu, 16 Feb 2017, Richard Biener wrote:

> 
> I am testing the following patch for PR79547.  Those builtins do not
> return anything that can be used to re-construct the pointer(s) passed
> to them.
> 
> Queued for GCC 8.

Actually we need calluse constraints.  Thus adjusted as follows.

Richard.

2017-02-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79547
	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
	without any constraints.

	* gcc.dg/tree-ssa/strlen-2.c: New testcase.

On Fri, 17 Feb 2017, Richard Biener wrote:

> On Thu, 16 Feb 2017, Richard Biener wrote:
>
>>
>> I am testing the following patch for PR79547.  Those builtins do not
>> return anything that can be used to re-construct the pointer(s) passed
>> to them.
>>
>> Queued for GCC 8.
>
> Actually we need calluse constraints.  Thus adjusted as follows.
>
> Richard.
>
> 2017-02-17  Richard Biener  <rguenther@suse.de>
>
> 	PR tree-optimization/79547
> 	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
> 	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
> 	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
> 	without any constraints.

We have EAF_NOESCAPE that we are using for non-builtins, though it 
probably gets little use there. Would it make sense to use it here as 
well, or would that be pointless?

On Fri, 17 Feb 2017, Marc Glisse wrote:

> On Fri, 17 Feb 2017, Richard Biener wrote:
> 
> > On Thu, 16 Feb 2017, Richard Biener wrote:
> > 
> > > 
> > > I am testing the following patch for PR79547.  Those builtins do not
> > > return anything that can be used to re-construct the pointer(s) passed
> > > to them.
> > > 
> > > Queued for GCC 8.
> > 
> > Actually we need calluse constraints.  Thus adjusted as follows.
> > 
> > Richard.
> > 
> > 2017-02-17  Richard Biener  <rguenther@suse.de>
> > 
> > 	PR tree-optimization/79547
> > 	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
> > 	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
> > 	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
> > 	without any constraints.
> 
> We have EAF_NOESCAPE that we are using for non-builtins, though it probably
> gets little use there. Would it make sense to use it here as well, or would
> that be pointless?

EAF_NOESCAPE doesn't capture what we want here -- for pure and const
functions arguments already don't escape in EAF_NOESCAPEs sense it's
just that EAF_NOESCAPE doesn't cover "escaping" through the return value.
We do not have sth like ERF_RETURNS_NO_ARG.

Generally all explicitely handled builtins do not need any further
fn-spec attributes added in builtins.def.

Richard.

On Fri, 17 Feb 2017, Richard Biener wrote:

> On Thu, 16 Feb 2017, Richard Biener wrote:
> 
> > 
> > I am testing the following patch for PR79547.  Those builtins do not
> > return anything that can be used to re-construct the pointer(s) passed
> > to them.
> > 
> > Queued for GCC 8.
> 
> Actually we need calluse constraints.  Thus adjusted as follows.

Re-bootstrapped & tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

> Richard.
> 
> 2017-02-17  Richard Biener  <rguenther@suse.de>
> 
> 	PR tree-optimization/79547
> 	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
> 	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
> 	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
> 	without any constraints.
> 
> 	* gcc.dg/tree-ssa/strlen-2.c: New testcase.
> 
> Index: gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c	(nonexistent)
> +++ gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c	(working copy)
> @@ -0,0 +1,15 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-strlen" } */
> +
> +void f (unsigned);
> +
> +void f3 (void)
> +{
> +  char s[] = "1234";
> +
> +  f (__builtin_strlen (s));
> +  f (__builtin_strlen (s));
> +  f (__builtin_strlen (s));
> +}
> +
> +/* { dg-final { scan-tree-dump-times "strlen" 1 "strlen" } } */
> Index: gcc/tree-ssa-structalias.c
> ===================================================================
> --- gcc/tree-ssa-structalias.c	(revision 245501)
> +++ gcc/tree-ssa-structalias.c	(working copy)
> @@ -4474,6 +4474,40 @@ find_func_aliases_for_builtin_call (stru
>  	    process_all_all_constraints (lhsc, rhsc);
>  	  }
>  	return true;
> +      /* Pure functions that return something not based on any object and
> +         that use the memory pointed to by their arguments (but not
> +	 transitively).  */
> +      case BUILT_IN_STRCMP:
> +      case BUILT_IN_STRNCMP:
> +      case BUILT_IN_STRCASECMP:
> +      case BUILT_IN_STRNCASECMP:
> +      case BUILT_IN_MEMCMP:
> +      case BUILT_IN_BCMP:
> +      case BUILT_IN_STRSPN:
> +      case BUILT_IN_STRCSPN:
> +	{
> +	  varinfo_t uses = get_call_use_vi (t);
> +	  make_any_offset_constraints (uses);
> +	  make_constraint_to (uses->id, gimple_call_arg (t, 0));
> +	  make_constraint_to (uses->id, gimple_call_arg (t, 1));
> +	  /* No constraints are necessary for the return value.  */
> +	  return true;
> +	}
> +      case BUILT_IN_STRLEN:
> +	{
> +	  varinfo_t uses = get_call_use_vi (t);
> +	  make_any_offset_constraints (uses);
> +	  make_constraint_to (uses->id, gimple_call_arg (t, 0));
> +	  /* No constraints are necessary for the return value.  */
> +	  return true;
> +	}
> +      case BUILT_IN_OBJECT_SIZE:
> +      case BUILT_IN_CONSTANT_P:
> +	{
> +	  /* No constraints are necessary for the return value or the
> +	     arguments.  */
> +	  return true;
> +	}
>        /* Trampolines are special - they set up passing the static
>  	 frame.  */
>        case BUILT_IN_INIT_TRAMPOLINE:
> 
>