On 09/09/2022 15:31, Jakub Jelinek wrote:
>> --- a/gcc/tree-if-conv.cc
>> +++ b/gcc/tree-if-conv.cc
>> @@ -1074,13 +1076,19 @@ if_convertible_stmt_p (gimple *stmt, vec<data_reference_p> refs)
>>   	tree fndecl = gimple_call_fndecl (stmt);
>>   	if (fndecl)
>>   	  {
>> +	    /* We can vectorize some builtins and functions with SIMD
>> +	       clones.  */
>>   	    int flags = gimple_call_flags (stmt);
>> +	    struct cgraph_node *node = cgraph_node::get (fndecl);
>>   	    if ((flags & ECF_CONST)
>>   		&& !(flags & ECF_LOOPING_CONST_OR_PURE)
>> -		/* We can only vectorize some builtins at the moment,
>> -		   so restrict if-conversion to those.  */
>>   		&& fndecl_built_in_p (fndecl))
>>   	      return true;
>> +	    else if (node && node->simd_clones != NULL)
>> +	      {
>> +		need_to_predicate = true;
> 
> I think it would be worth it to check that at least one of the
> node->simd_clones clones has ->inbranch set, because if all calls
> are declare simd notinbranch, then predicating the loop will be just a
> wasted effort.
> 
>> +		return true;
>> +	      }
>>   	  }
>>   	return false;
>>         }
>> @@ -2614,6 +2622,31 @@ predicate_statements (loop_p loop)
>>   	      gimple_assign_set_rhs1 (stmt, ifc_temp_var (type, rhs, &gsi));
>>   	      update_stmt (stmt);
>>   	    }
>> +
>> +	  /* Add a predicate parameter to functions that have a SIMD clone.
>> +	     This will cause the vectorizer to match the "in branch" clone
>> +	     variants because they also have the extra parameter, and serves
>> +	     to build the mask vector in a natural way.  */
>> +	  gcall *call = dyn_cast <gcall *> (gsi_stmt (gsi));
>> +	  if (call && !gimple_call_internal_p (call))
>> +	    {
>> +	      tree orig_fndecl = gimple_call_fndecl (call);
>> +	      int orig_nargs = gimple_call_num_args (call);
>> +	      auto_vec<tree> args;
>> +	      for (int i=0; i < orig_nargs; i++)
>> +		args.safe_push (gimple_call_arg (call, i));
>> +	      args.safe_push (cond);
>> +
>> +	      /* Replace the call with a new one that has the extra
>> +		 parameter.  The FUNCTION_DECL remains unchanged so that
>> +		 the vectorizer can find the SIMD clones.  This call will
>> +		 either be deleted or replaced at that time, so the
>> +		 mismatch is short-lived and we can live with it.  */
>> +	      gcall *new_call = gimple_build_call_vec (orig_fndecl, args);
>> +	      gimple_call_set_lhs (new_call, gimple_call_lhs (call));
>> +	      gsi_replace (&gsi, new_call, true);
> 
> I think this is way too dangerous to represent conditional calls that way,
> there is nothing to distinguish those from non-conditional calls.
> I think I'd prefer (but please see what Richi thinks too) to represent
> the conditional calls as a call to a new internal function, say
> IFN_COND_CALL or IFN_MASK_CALL, which would have the arguments the original
> call had, plus 2 extra ones first (or 3?), one that would be saved copy of
> original gimple_call_fn (i.e. usually &fndecl), another one that would be the
> condition (and dunno about whether we need also something to represent
> gimple_call_fntype, or whether we simply should punt during ifcvt
> on conditional calls where gimple_call_fntype is incompatible with
> the function type of fndecl.  Another question is about
> gimple_call_chain.  Punt or copy it over to the ifn and back.

The attached should resolve these issues.

OK for mainline?

Andrew