Re: [2/2] PR96463 -- changes to type checking vec_perm_expr in middle end

[Richard Sandiford <richard.sandiford@arm.com>]

Richard Biener <rguenther@suse.de> writes:
> On Fri, 17 Dec 2021, Richard Sandiford wrote:
>
>> Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
>> > Hi,
>> > The attached patch rearranges order of type-check for vec_perm_expr
>> > and relaxes type checking for
>> > lhs = vec_perm_expr<rhs1, rhs2, mask>
>> >
>> > when:
>> > rhs1 == rhs2,
>> > lhs is variable length vector,
>> > rhs1 is fixed length vector,
>> > TREE_TYPE (lhs) == TREE_TYPE (rhs1)
>> >
>> > I am not sure tho if this check is correct ? My intent was to capture
>> > case when vec_perm_expr is used to "extend" fixed length vector to
>> > it's VLA equivalent.
>> 
>> VLAness isn't really the issue.  We want the same thing to work for
>> -msve-vector-bits=256, -msve-vector-bits=512, etc., even though the
>> vectors are fixed-length in that case.
>> 
>> The principle is that for:
>> 
>>   A = VEC_PERM_EXPR <B, C, D>;
>> 
>> the requirements are:
>> 
>> - A, B, C and D must be vectors
>> - A, B and C must have the same element type
>> - D must have an integer element type
>> - A and D must have the same number of elements (NA)
>> - B and C must have the same number of elements (NB)
>> 
>> The semantics are that we create a joined vector BC (all elements of B
>> followed by all element of C) and that:
>> 
>>   A[i] = BC[D[i] % (NB+NB)]
>> 
>> for 0 ≤ i < NA.
>> 
>> This operation makes sense even if NA != NB.
>
> But note that we don't currently expect NA != NB and the optab just
> has a single mode.

True, but we only need this for constant permutes.  They are already
special in that they allow the index elements to be wider than the data
elements.

Thanks,
Richard

>
> I'd rather go with the simpler patch I posted as reply to the earlier
> mail rather such large refactoring at this point.
>
> Richard.
>
>> Thanks,
>> Richard
>> 
>> >
>> > Thanks,
>> > Prathamesh
>> >
>> > diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
>> > index 672e384ef09..9f91878c468 100644
>> > --- a/gcc/tree-cfg.c
>> > +++ b/gcc/tree-cfg.c
>> > @@ -4325,10 +4325,11 @@ verify_gimple_assign_ternary (gassign *stmt)
>> >        break;
>> >  
>> >      case VEC_PERM_EXPR:
>> > -      if (!useless_type_conversion_p (lhs_type, rhs1_type)
>> > -	  || !useless_type_conversion_p (lhs_type, rhs2_type))
>> > +      if (TREE_CODE (rhs1_type) != VECTOR_TYPE
>> > +	  || TREE_CODE (rhs2_type) != VECTOR_TYPE
>> > +	  || TREE_CODE (rhs3_type) != VECTOR_TYPE)
>> >  	{
>> > -	  error ("type mismatch in %qs", code_name);
>> > +	  error ("vector types expected in %qs", code_name);
>> >  	  debug_generic_expr (lhs_type);
>> >  	  debug_generic_expr (rhs1_type);
>> >  	  debug_generic_expr (rhs2_type);
>> > @@ -4336,11 +4337,14 @@ verify_gimple_assign_ternary (gassign *stmt)
>> >  	  return true;
>> >  	}
>> >  
>> > -      if (TREE_CODE (rhs1_type) != VECTOR_TYPE
>> > -	  || TREE_CODE (rhs2_type) != VECTOR_TYPE
>> > -	  || TREE_CODE (rhs3_type) != VECTOR_TYPE)
>> > +      if (TREE_CODE (TREE_TYPE (rhs3_type)) != INTEGER_TYPE
>> > +	  || (TREE_CODE (rhs3) != VECTOR_CST
>> > +	      && (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE
>> > +				    (TREE_TYPE (rhs3_type)))
>> > +		  != GET_MODE_BITSIZE (SCALAR_TYPE_MODE
>> > +				       (TREE_TYPE (rhs1_type))))))
>> >  	{
>> > -	  error ("vector types expected in %qs", code_name);
>> > +	  error ("invalid mask type in %qs", code_name);
>> >  	  debug_generic_expr (lhs_type);
>> >  	  debug_generic_expr (rhs1_type);
>> >  	  debug_generic_expr (rhs2_type);
>> > @@ -4348,15 +4352,18 @@ verify_gimple_assign_ternary (gassign *stmt)
>> >  	  return true;
>> >  	}
>> >  
>> > -      if (maybe_ne (TYPE_VECTOR_SUBPARTS (rhs1_type),
>> > -		    TYPE_VECTOR_SUBPARTS (rhs2_type))
>> > -	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs2_type),
>> > -		       TYPE_VECTOR_SUBPARTS (rhs3_type))
>> > -	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs3_type),
>> > -		       TYPE_VECTOR_SUBPARTS (lhs_type)))
>> > +      /* Accept lhs = vec_perm_expr<v, v, mask> if lhs is vector length agnostic,
>> > +	 and has same element type as v.  */
>> > +      if (!TYPE_VECTOR_SUBPARTS (lhs_type).is_constant ()
>> > +	  && operand_equal_p (rhs1, rhs2, 0)
>> > +	  && TYPE_VECTOR_SUBPARTS (rhs1_type).is_constant ()
>> > +	  && TREE_TYPE (lhs_type) == TREE_TYPE (rhs1_type)) 
>> > +	return false;
>> > +
>> > +      if (!useless_type_conversion_p (lhs_type, rhs1_type)
>> > +	  || !useless_type_conversion_p (lhs_type, rhs2_type))
>> >  	{
>> > -	  error ("vectors with different element number found in %qs",
>> > -		 code_name);
>> > +	  error ("type mismatch in %qs", code_name);
>> >  	  debug_generic_expr (lhs_type);
>> >  	  debug_generic_expr (rhs1_type);
>> >  	  debug_generic_expr (rhs2_type);
>> > @@ -4364,21 +4371,21 @@ verify_gimple_assign_ternary (gassign *stmt)
>> >  	  return true;
>> >  	}
>> >  
>> > -      if (TREE_CODE (TREE_TYPE (rhs3_type)) != INTEGER_TYPE
>> > -	  || (TREE_CODE (rhs3) != VECTOR_CST
>> > -	      && (GET_MODE_BITSIZE (SCALAR_INT_TYPE_MODE
>> > -				    (TREE_TYPE (rhs3_type)))
>> > -		  != GET_MODE_BITSIZE (SCALAR_TYPE_MODE
>> > -				       (TREE_TYPE (rhs1_type))))))
>> > +      if (maybe_ne (TYPE_VECTOR_SUBPARTS (rhs1_type),
>> > +		    TYPE_VECTOR_SUBPARTS (rhs2_type))
>> > +	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs2_type),
>> > +		       TYPE_VECTOR_SUBPARTS (rhs3_type))
>> > +	  || maybe_ne (TYPE_VECTOR_SUBPARTS (rhs3_type),
>> > +		       TYPE_VECTOR_SUBPARTS (lhs_type)))
>> >  	{
>> > -	  error ("invalid mask type in %qs", code_name);
>> > +	  error ("vectors with different element number found in %qs",
>> > +		 code_name);
>> >  	  debug_generic_expr (lhs_type);
>> >  	  debug_generic_expr (rhs1_type);
>> >  	  debug_generic_expr (rhs2_type);
>> >  	  debug_generic_expr (rhs3_type);
>> >  	  return true;
>> >  	}
>> > -
>> >        return false;
>> >  
>> >      case SAD_EXPR:
>>