[PATCH v4 2/7] Introduce can_vcond_compare_p function

[Ilya Leoshkevich]

> Am 03.10.2019 um 14:42 schrieb Richard Sandiford <richard.sandiford@arm.com>:
> 
> Ilya Leoshkevich <iii@linux.ibm.com> writes:
>> z13 supports only non-signaling vector comparisons.  This means we
>> cannot vectorize LT, LE, GT, GE and LTGT when compiling for z13.
>> However, we cannot express this restriction today: the code only checks
>> whether vcond$a$b optab exists, which does not contain information about
>> the operation.
>> 
>> Introduce a function that checks whether back-end supports vector
>> comparisons with individual rtx codes by matching vcond expander's third
>> argument with a fake comparison with the corresponding rtx code.
>> 
>> gcc/ChangeLog:
>> 
>> 2019-08-27  Ilya Leoshkevich  <iii@linux.ibm.com>
>> 
>> 	PR target/77918
>> 	* optabs-tree.c (vcond_icode_p): New function.
>> 	(vcond_eq_icode_p): New function.
>> 	(expand_vec_cond_expr_p): Use vcond_icode_p and
>> 	vcond_eq_icode_p.
>> 	* optabs.c (can_vcond_compare_p): New function.
>> 	(get_rtx_code): Use get_rtx_code_safe.
>> 	(get_rtx_code_safe): New function.
>> 	* optabs.h (can_vcond_compare_p): New function.
>> 	(get_rtx_code_safe): Likewise.
>> ---
>> gcc/optabs-tree.c | 37 +++++++++++++++++++++++++++++++------
>> gcc/optabs.c      | 38 ++++++++++++++++++++++++++++++++++----
>> gcc/optabs.h      |  7 +++++++
>> 3 files changed, 72 insertions(+), 10 deletions(-)
>> 
>> diff --git a/gcc/optabs-tree.c b/gcc/optabs-tree.c
>> index 8157798cc71..7f505c9cdee 100644
>> --- a/gcc/optabs-tree.c
>> +++ b/gcc/optabs-tree.c
>> @@ -23,7 +23,10 @@ along with GCC; see the file COPYING3.  If not see
>> #include "coretypes.h"
>> #include "target.h"
>> #include "insn-codes.h"
>> +#include "rtl.h"
>> #include "tree.h"
>> +#include "memmodel.h"
>> +#include "optabs.h"
>> #include "optabs-tree.h"
>> #include "stor-layout.h"
>> 
>> @@ -329,6 +332,28 @@ expand_vec_cmp_expr_p (tree value_type, tree mask_type, enum tree_code code)
>>   return false;
>> }
>> 
>> +/* Return true iff vcond_optab/vcondu_optab support the given tree
>> +   comparison.  */
> 
> Realise it's a bit repetitive in the context of this patch, but...
> 
> /* Return true iff vcond_optab/vcondu_optab can handle a vector
>   comparison for code CODE, comparing operands of type CMP_OP_TYPE and
>   producing a result of type VALUE_TYPE.  */
> 
>> +
>> +static bool
>> +vcond_icode_p (tree value_type, tree cmp_op_type, enum tree_code code)
>> +{
>> +  return can_vcond_compare_p (get_rtx_code (code, TYPE_UNSIGNED (cmp_op_type)),
>> +			      TYPE_MODE (value_type), TYPE_MODE (cmp_op_type));
>> +}
>> +
>> +/* Return true iff vcondeq_optab supports the given tree comparison.  */
> 
> Same idea here.
> 
>> +
>> +static bool
>> +vcond_eq_icode_p (tree value_type, tree cmp_op_type, enum tree_code code)
>> +{
>> +  if (code != EQ_EXPR && code != NE_EXPR)
>> +    return false;
>> +
>> +  return get_vcond_eq_icode (TYPE_MODE (value_type), TYPE_MODE (cmp_op_type))
>> +	 != CODE_FOR_nothing;
>> +}
>> +
>> /* Return TRUE iff, appropriate vector insns are available
>>    for vector cond expr with vector type VALUE_TYPE and a comparison
>>    with operand vector types in CMP_OP_TYPE.  */
>> @@ -347,14 +372,14 @@ expand_vec_cond_expr_p (tree value_type, tree cmp_op_type, enum tree_code code)
>>       || maybe_ne (GET_MODE_NUNITS (value_mode), GET_MODE_NUNITS (cmp_op_mode)))
>>     return false;
>> 
>> -  if (get_vcond_icode (TYPE_MODE (value_type), TYPE_MODE (cmp_op_type),
>> -		       TYPE_UNSIGNED (cmp_op_type)) == CODE_FOR_nothing
>> -      && ((code != EQ_EXPR && code != NE_EXPR)
>> -	  || get_vcond_eq_icode (TYPE_MODE (value_type),
>> -				 TYPE_MODE (cmp_op_type)) == CODE_FOR_nothing))
>> +  if (get_rtx_code_safe (code, TYPE_UNSIGNED (cmp_op_type))
>> +      == LAST_AND_UNUSED_RTX_CODE)
>> +    /* This may happen, for example, if code == SSA_NAME, in which case we
>> +       cannot be certain whether a vector insn is available.  */
>>     return false;
> 
> I think this should just be:
> 
>  if (TREE_CODE_CLASS (tcode) != tcc_comparison)
>    return false;
> 
> OK with those changes and without the introduction of get_rtx_code_safe.

Thanks! I've made the changes, retested, and committed the result as
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=276660
alongside
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=276659
which Richard B. has approved as well.

Now only the main S/390 bits remain..

Best regards,
Ilya